AQA Biology A-Level

#separator:tab #html:true Why is (control) used?- as a control<div>- to show effect of x<br><div>- to show that x does not affect results</div><div>- to show that <b>only</b> y causes the change</div><div>- may be used as baseline value to investigate effect of treatments</div></div> Why is a representative sample important?- more reliable mean "Mitosis is important in the life of an organism. State reasons why. [4] MS "1. Growth / increase in cell number;<br>2. Replace cells / repair tissue / organs / body;<br>3. Genetically identical cells;<br>4. Asexual reproduction / cloning;<br><br> "A decrease in temperature decreases the kinetic energy of molecules in a solution. Explain how a decrease in temperature decreases the rate of an enzyme-controlled reaction. MS [2] "<ul><li>molecules moving less/slower;</li><li>reduces chance of collision (between enzyme and substrate)/of enzyme-substrate complexes being formed;</li></ul> "Explain why an electron microscope shows more detail of cell structure than a light microscope [2] ""<ul><li>electron microscope has a <b><font color=""#ff0000"">greater resolving power</font></b> / objects closer together can be distinguished</li><li>electron (beams) have a<b><font color=""#ff0000""> shorter wavelength</font></b>;</li></ul>" "Abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of the insect. Explain why. ( 2 marks) "More air / oxygen enters / air / oxygen enters quickly / quicker;<br><div><br></div><div>(So) maintains / greater diffusion or concentration gradient;<br></div> Recall the uses of ATP. [6]<br><div><br></div>provides energy for <div><br><div>- synthesis of macromolecules<div>- muscle contraction</div></div><div>- active transport</div><div>- secretion</div><div><br></div><div><br></div><div>Phosphate Released:</div><div>- phosphorylation of molecules<br></div></div><div>- can active other key bio molecules</div> What are the 3 aspects to consider when choosing a temperature for an experiment?- sufficient kinetic energy<div>- does not denature proteins</div><div>- <b>optimum</b></div> Explain the function of the golgi apparatus + vesicles"<ul><li><font color=""#ff0000"">Packages and mods proteins </font>(e.g adding a carbohydrate to it)</li><li>Vesicles transport proteins + lipids  out of the cell to the CS membrane (using exocytosis)</li></ul>" How are photomicrographs formed using a TEM?"<ul><li>e<sup>-</sup> gun produces a beam of e<sup>-</sup> -> focused on specimen by electromagnet.</li><li>beam <font color=""#ff0000"">passes through specimen</font>, denser areas are absorbed causing dark spots.</li></ul>" How are SEM images created?<div><ul><li>e<sup>- </sup> beam is directed from above</li><li>e<sup>- </sup> beams are scattered which are analysed by a computer to build a 3-D image.</li></ul></div><div><br></div> what are the functions of glycoproteins? [2]- act as recognition sites<div>- help cells attach to one another + form tissues </div><div>(e.g lymphocytes can recognise an organism's own cells)</div> How do desert animals with a high SA:V ratio reduce water loss? (e.g adaptations)<ul><li>adaptations to kidney structure to produce less urine. (longer loops of Henle)</li></ul> State the 3 products of the light- dependent reaction.Reduced NADP, ATP & O<sub>2 </sub> Where does the light independent reaction occur?In the stroma Where does the light dependent reaction occur?In the thylakoids State the products of the light independent reaction [2]Sugars (e.g glucose) and organic molecules. Explain photoionisation and chemiosmosis. [3]"1. Photoionisation of chlorophyll a (PS II) causes an e<sup>- </sup> to become <font color=""#ff0000"">excited.</font><div><font color=""#ff0000""><br></font></div><div>2. The e<sup>- </sup><sub> </sub>travels DOWN the ETC and <font color=""#ff0000"">loses energy as it goes down</font> (energy is used to pump H<sup>+ </sup>across the thylakoid membrane)</div><div><br></div><div>3. <font color=""#ff0000"">H<sup>+ </sup>diffuses out of the thylakoid membrane through ATP synthase, which provides energy for an ADP + Pi molecule to form ATP</font> (chemiosmosis= movement of ions across a semi perm-membrane, down their electro chemical gradient)</div>" Explain how reduced NADP is formed. [3]"1. Photoactivation of chlorophyll a (PS II) causes <font color=""#ff0000"">photolysis</font>:<div><br><div>H<sub>2</sub>O molecule to be split into hydrogen ions, electrons and an Oxygen molecule<div><div><br></div><div>2. Oxygen diffuses out of the chloroplast via the stomata</div><div><br></div><div>3. <font color=""#ff0000"">H<sup>+ </sup>reduces NADP</font><sup><font color=""#ff0000"">+</font> </sup> to produce reduced NADP (aka NADPH).</div></div></div></div>" What is the general formula for monosaccharides?(CH<sub>2</sub>0)<sub>n</sub> Why are unsaturated lipids liquid at room temperature?The precense of the double bond means that the molecule is able to bend. As a result, the unsaturated fats cannot pack together as tightly, hence it's liquid at room temperature.  "Saturated lipids are found in <span class=""cloze"" data-cloze=""animals"" data-ordinal=""1"">[...]</span> whilst unsaturated lipids are found in <span class=""cloze"" data-cloze=""plants"" data-ordinal=""1"">[...]</span>""Saturated lipids are found in <span class=""cloze"" data-ordinal=""1"">animals</span> whilst unsaturated lipids are found in <span class=""cloze"" data-ordinal=""1"">plants</span><br> " Illustrate the formation of a Dipeptide"<img src=""dd732e5f03c98729f4b843329cdc444b.png"">" Why do hydrogen bonds form in the secondary structure?The hydrogen in the -NH has a slight positive charge whilst the oxygen in the -C=O has a slight negative charge. "Proteins can be either <span class=""cloze"" data-cloze=""globular"" data-ordinal=""1"">[...]</span> or <span class=""cloze"" data-cloze=""fibrous"" data-ordinal=""1"">[...]</span>. ""Proteins can be either <span class=""cloze"" data-ordinal=""1"">globular</span> or <span class=""cloze"" data-ordinal=""1"">fibrous</span>. <br> " "All <span class=""cloze"" data-cloze=""polysaccharides"" data-ordinal=""1"">[...]</span> and some <span class=""cloze"" data-cloze=""disaccharides"" data-ordinal=""1"">[...]</span> are non-reducing sugars""All <span class=""cloze"" data-ordinal=""1"">polysaccharides</span> and some <span class=""cloze"" data-ordinal=""1"">disaccharides</span> are non-reducing sugars<br> " Contrast DNA and RNA<div>in terms of:<br><div> - Name</div><div> - Chain Length</div><div> - Strand Number</div><div> - Pentose Sugar</div><div> - Organic Bases</div><div> - Chemical Stability</div><div> - Function</div></div>"<img src=""paste-81b9f50368a3a4dd91ffc8a2394834287e2a8e48.jpg""><br>" Describe the structure of RNA (5)1) single stranded<div>2) short polynucleotides<br></div><div>3) ribose sugar</div><div>4) bases: uracil, guanine, cytosine, adenine</div><div>5) less stable</div><div><br></div> Explain why, in semi-conservative DNA replication, that DNA polymerase works in different directions<div>(1) The two strands of DNA are antiparallel to each other</div><div>(2) The alignment / orientation of the nucleotides are arranged differently</div><div>(3) Enzymes have active sites with a specific shape</div><div>(4) Only substrates will the complementary shape and orientation will be able to bind to the active site of DNA polymerase </div><div><br></div> Illustrate the reaction of ADP + Pi, labelling the enzymes and names of the reaction"<img src=""8a80ff5f754ed117c69874b719dae553.png"">" Discuss the advantages and disadvantages of using a transmission electron microscope."<font color=""#d694ff"">Advantages:</font><div><ul><li>Best magnification and resolution</li><li>Allows internal structures to be seen</li></ul></div><div><br></div><div><font color=""#d694ff"" style="""">Disadvantages:</font></div><div><ul><li>Can't look at living cells → specimen need to be in a vacuum</li><li>Specimen must be very thin</li><li>Artefacts present</li><li>Long preparation time and complex staining process</li><li>Doesn't form a colour image</li><li>Only 2D images produced</li></ul></div>" Name 2 alternative respiratory substrates.<ul><li>Lipids</li><li>Proteins</li></ul> Explain how proteins enter the Krebs Cycle. [3]<div><ul><li>hydrolysed into AA</li><li>deamination</li><li>enters pathway at diff. points depending on number of carbons (3Cs converted to pruvate, 4+5Cs conveted to KCycle intermediates)</li></ul></div> What are lysosomes and their function?"<ul><li>Membrane-bound vesicles found in the cytoplasm that contain a <font color=""#ff0000"">hydrolytic enzyme called lysozyme.</font></li><li>They are responsible for digesting invading cells / breaking down work out components</li></ul>" Recall the structure of chloroplasts [7]"1. Small, flattened structure found within plant and algae cells<div>2. Contains a double membrane</div><div>3. Stroma is an aqueous liquid found within these membranes (contains enzymes)</div><div>4. Contains structures within called thylakoids</div><div>5. Stacked thylakoids = grana</div><div>6. Grana linked to each other by thin, flat  piece of membrane called a lamellae </div><div>7. Contains circular DNA and ribosomes</div><div><br></div><div><br></div><div><img src=""chloroplastdiagram.jpg""><br></div>" What do prokaryotic cells have instead of Mitochondria?Mesosomes - these are in foldings of the cell membrane that provide a large surface area for the attachment of the enzymes involved in respiration.  Explain why phospholipids form a bilayer in plasma membranes1) Phospholipids have a <b>polar </b>phosphate group which are <b>hydrophilic </b>and will face the aqueous solutions<div>2) The fatty acid tails are <b>non-pola</b>r and will <b>move away </b>from an aqueous envrionment</div><div>3) As both the <b>intracellular </b>fluid (cytoplasm) and <b>extracellular </b>fluid (tissue fluid) is <b>aqueous</b>, phospholipids form <b>two layers </b>with the <b>hydrophobic tails facing inwards </b>and the phosphate groups <b>facing outwards,</b> interacting with the aqueous environment. </div> "Outline the steps in preparing<span style=""color: var(--field-fg); background: var(--field-bg);""> a ''temporary mount''</span>"<ul><li>Start by pipetting a small drop of water onto the slide </li><li>Use <b>tweezers </b>to place a <b>thin section </b>on top of the water drop</li><li>Add a drop of <b>stain</b>, e.g eosin to make cytoplasm show up</li><li>Use a <b>mounted needle </b>to add a <b>cover slip</b> to protect the specimen. Try and avoid air bubbles. </li></ul> Describe the function of cholesterol in the cell membraneCholestrol regulates the fluidity of the cell-surface membrane. <div><br></div><div>Key Functions:</div><div>- reduces lateral movement of other molecules including phospholipids</div><div>- makes the membrane less fluid at high temperatures</div><div>- prevent leakage of water and dissolved ions from the cell as it is hydrophobic</div> "The centre of the bilayer is <span class=""cloze"" data-cloze=""hydrophobic"" data-ordinal=""1"">[...]</span> so <span class=""cloze"" data-cloze=""water-soluble substances"" data-ordinal=""1"">[...]</span> can't easily pass through it. ""The centre of the bilayer is <span class=""cloze"" data-ordinal=""1"">hydrophobic</span> so <span class=""cloze"" data-ordinal=""1"">water-soluble substances</span> can't easily pass through it. <br> " State the adaptations of the plasma membrane for its functions [6] 1. phospholipid bilayer forms a barrier (forms a barrier to water soluble substances)<div>2. fluid (can bend to take up differnet shapes, e.g to form vesicles / self repair)</div><div>3. channel proteins (let water soluble/charged particels substances through)</div><div>4. carrier proteins (allow for facilitated diffusion)</div><div>5. surface proteins (act as receptors)</div><div>6. cholesterol (regulates fluidity)</div> What is the limitation of the lock and key model?<div><ul><li>Suggested AS of an enzyme is <b>rigid</b></li><li>Scientists observed inhibitors could bind</li><li>Hence enzymes shape was being altered by binding molecule</li></ul></div> Describe how substances move across cell surface membranes by facilitated diffusion MS [3]1. Carrier / Channel Protein<div>2. Protein's are specific to substance</div><div>3. Substance moves down the concentration gradient </div> Compare and contrast facilitated and simple diffusion<b>Similarities:</b><div>Passive</div><div>Particles move down their concentration gradient</div><div><br><b>Differences:</b></div><div>Facilitated Diffusion uses transport proteins e.g carrier/channel</div> "<img src=""be2ff8fb1a31473feebcb0f821511e14.png"">Explain why the graph for facilitated diffusion levels off"The curve levels off above a certain external concentration of substance as channel proteins are saturated with molecules.  Contrast hypotonic vs hypertonicHypotonic - a solution with <b>more water </b>and less solute<div><br></div><div>Hypertonic - a soluton with <b>less water </b>and more solute</div> What happens when you put an animal cell in pure water?"<div>swells and burst (water enters by osmosis)</div>" What happens when you put a plant cell in pure water?"<div>-        swells but does not burst</div> <div>-        cell wall prevents it from bursting</div> <div>-        made of cellulose – strong material</div> <div>-        the cell is <u>Turgid (swollen)</u></div>" What happens when you put plant clels in concentrated sugar solution?-   The cytoplasm and vacuole shrink and membrane pulls away from the cell wall<br><div>- Becomes plasmolysed</div> In some scenarios, more than one ion is transported using the same carrier protein. Describe an example fo this."SODIUM POTASSIUM PUMP<div><br></div><div>1. The sodium-potassium pump binds three sodium ions and a molecule of ATP (from inside the cell)</div><div><br></div><div>2. The splitting of ATP provides energy to change the shape of the channel. The sdoium ions are driven through the channel.</div><div><br></div><div>3. The sodium ions are released to the outside of the membrane, and the new shape of the channel allows two potassium ions to bind.</div><div><br></div><div>4. Release of the phosphate reverts the channel to its original form, releasing potassium ions on the inside of the membrane. </div><div><br></div><div><img src=""2417cef5306545260224a34f5f0418b2.png""><br><div><br></div></div>" Why would the loss of water kill bacterial/plant cells?Loss of water will stop metabolic reactions State the relationship between specialised cells and organ systemsSpecialised cells form tissues that perform specific functions. These form organs made of several tissue types, which form organ systems What is the name of the liquid which bathes cells in insects?Haemolymph Suggest why genetically identical twins often show slight differences in their appearance MS [1]Environmental factors during pregnancy. (E.g nutrient supply) Define evolution.Change in allele frequency in a population over time. Explain how natural selection causes evolution [This concept can be applied to any exam Q]"1. <font color=""#ff453a"">Variation</font> within a population due to <font color=""#ff453a"">mutation</font><div><br></div><div><span style=""caret-color: rgb(255, 69, 58);"">2. <font color=""#ff453a"">Selection Pressure</font> (e.g. predation, climate disease , competition) => struggle for survival</span></div><div><span style=""caret-color: rgb(255, 69, 58);""><br></span></div><div><span style=""caret-color: rgb(255, 69, 58);"">3. Some organisms have alleles that are more favourable to the selection pressure</span></div><div><span style=""caret-color: rgb(255, 69, 58);""><br></span></div><div><span style=""caret-color: rgb(255, 69, 58);"">4. These organisms are <font color=""#ff453a"">more likely to survive and reproduce</font>, producing more offspring and <font color=""#ff453a"">passing on their favourable alleles to the next gen. </font><u style="""">(differential reproductive success)</u></span></div><div><span style=""caret-color: rgb(255, 69, 58);""><br></span></div><div><span style=""caret-color: rgb(255, 69, 58);"">5. <font color=""#ff453a"">Allele frequencies</font> in gene pool <font color=""#ff453a"">change over many generations</font></span></div>" Explain the effects of directional selection."- Selective pressures / environment favour individuals favourable allele combination <font color=""#ff453a"">one direction from the mean.</font><div><br></div><div>- <font color=""#ff453a"">Mean shifts</font> in direction of favourable allele / phenotype</div><div><br></div>" Explain the main effects of stabilising selection. [3]"- Selective pressures favour the mean/ <font color=""#ff453a"">acts against the 2 extremes of a characteristic.</font><div><span style=""caret-color: rgb(255, 69, 58);"">- Individuals with extreme phenotypes less likely to survive <font color=""#ff453a"">(standard deviation gets smaller over time)</font></span><br></div><div><span style=""caret-color: rgb(255, 69, 58);"">- <font color=""#ff453a"">Mean stays the same</font></span></div><div><span style=""caret-color: rgb(255, 69, 58);"">- e.g human birth weight</span></div>" Explain the effects of disruptive selection."- Selection against the <font color=""#ff453a"">mean</font><div><span style=""caret-color: rgb(255, 69, 58);"">- Population becomes phenotypically divided - favours both extremes</span></div><div><span style=""caret-color: rgb(255, 69, 58);"">- Could result in <font color=""#ff453a"">2 separate species</font></span></div><div><span style=""caret-color: rgb(255, 69, 58);"">E.g Californian salamander</span></div>" Describe and explain differences in sensitivity to light between rods and cones. [5]"<font color=""#ff0000"">Rods are more sensitive to light</font><div><div>- They are connected in groups to one bipolar neurone</div></div><div>- Spatial summation</div><div>- Stimulation of each individual rod cell is insufficent, however, because they are connected in groups the threshold is more likely to be exceeded to generate an action potential.</div><div><span style=""color: rgb(255, 0, 0);""><br></span></div><div><span style=""color: rgb(255, 0, 0);"">Cones are less sensitive to light</span><br></div><div>- One cone joins to one neurone</div><div>- No spatial summation</div><div>- Threshold not reached during exposure to low levels of light </div><div><img src=""Compare-Rod-Cells-and-Cone-Cells.jpg""><br></div>" Describe and explain the differences in visual acuity between rod and cone cells."<div><div><font color=""#ff0000"">Rods give lower visual acuity:</font></div><div>- Rods connected in groups to one bipolar neurone</div><div>- Spatial summation</div><div>- Many neurones generate ONE action potential, regardless of the no. of neurones stimulated.</div><div>- Therefore they cannot distinguish between separate sources of light</div><div><br></div></div><font color=""#ff0000""><div><font color=""#ff0000""><br></font></div>Cones give a higher visual acuity:</font><div>- One cone joins to one neurone</div><div>- <font color=""#ff0000"">If 2 adjacent cones are stimulated, the brain recieves 2 separate impulses</font></div><div>- Therefore it can distinguish between <font color=""#ff0000"">2 separate sources</font> of light.</div><div><br></div><div><br></div><div><img src=""Compare-Rod-Cells-and-Cone-Cells.jpg""><br></div>" Describe and explain the differences between sensitivity to colour between rods and cones."<div><div><font color=""#ff0000""><br>Rods allow monochromatic vision</font></div><div>- One type of pigment (rodhopsin)</div></div><font color=""#ff0000""><div><br></div>Cones allow trichromatic vision</font><div>- 3 types of cones </div><div>- Different optical pigments (opsins) that absorb different wavelengths (red, green and blue)</div><div>- Stimulation of different combinations of cones give a range of colour perception.</div><div><br></div><div><br></div><div><br></div><div><img src=""Compare-Rod-Cells-and-Cone-Cells.jpg""><br></div>" Where are cone cells located in the eye?Concentrated at the fovea.<div><br></div><div>They need bright light to be stimulated</div> Where are rod cells located in the eye?In the periphery of the retina<div><br></div><div>Pigment are broken down by low intensity light.</div> What is the Chi-Squared test used for?To find out whether the difference between observed vs expected data is due to chance. Explain the relationship between SA:V and metabolic rate."<ul><li>Rate of heat loss increases as SA:V increases</li><li>(more heat loss per unit body mass in smaller animals with a high SA:V)</li><li>So they need a <font color=""#ff0000"">higher metabolic rate</font> / faster respiration</li><li>To generate enough heat to <font color=""#ff0000"">maintain a constant body temperature</font> (i.e replace lost heat)</li></ul>" In what organelle are starch grains found and why?Chloroplasts - starch grains are a product of photosynthesis What are the cells called that line the ileum and contain microvilli?Epithelial Cells How is the concentration gradient of glucose (higher in the illeum, lower in the bloodstream) maintained?<b>Blood is constantly being circulated</b> by the heart, the glucose absorbed into the bloodstream is taken around the body and <b>used in aerobic respiration. </b><div><br></div><div>This helps to maintain the concentration gradient and maintain the rate of diffusion. </div> Without mentioning co-transport, explain how the digestion of starch in the gut leads to an increase of glucose concentration in the blood.1) Hydrolysed by enzymes, (amylase)<div>2) Produces glucose in the gut</div><div>3) Glucose is small enough to cross the gut wall into the blood </div> Explain how epithelial cells absorb glucose via co-transport with sodium ions. MS [3]1. Sodium ions <b>actively transported</b> from the ileum cell to blood<div>2. This maintains the concentration gradient for sodium to enter from gut, each coupled with a glucose molecule</div><div>3. Glucose enters by <i>facilitated diffusion </i>via a co-transport protein with sodium ions</div> How would the addition of a respiratory inhibitor stop the absorption of amino acids in the ileum? MS [4]<div><br></div>1. No ATP produced<div>2. Sodium ions not moved out of the cell</div><div>3. No concentration gradient for sodium to move into the cell with amino acids, hence no amino acids are absorbed</div> What is the collective term for microvilli?brush border  How do you calculate SA:V ratio?Surface Area / Volume What are the 2 factors that affect the amount of each <b>material </b> that is exchanged from an organism?1. Size of the organism<div>2. Metabolic rate of the organism (higher metabolic rate = more materials)</div> Explain how rapid gaseous exchange takes place in a mammal MS [4]1. Large surface area provided by alveoli and capillary network<div>2. Concentration gradient maintained by ventilation of air in the lungs and circulation of blood</div><div>3. Diffusion pathway is small because capillaries and alveoli have a thin wall</div><div>4. Air is warmed because lungs are in core of the body, warmer air enables faster movement. </div> "When a living cell is surrounded by a cell wall, <span class=""cloze"" data-cloze=""this is no additional barrier to the diffusion of gases.&nbsp;"" data-ordinal=""1"">[...]</span>""When a living cell is surrounded by a cell wall, <span class=""cloze"" data-ordinal=""1"">this is no additional barrier to the diffusion of gases. </span><br> " What are tracheae?An internal network of tubes present in insects that allow for gas exchange What do tracheae divide into? How is this beneficial?They divide into samller dead-end tubes called tracheoles, these extend throughout all the body tissues of the insect. <div><br></div><div>This means that oxygen is taken directly to respiring tissues, hence the diffusion pathway is short. </div> 6.5 - Why do insects leave their spiracles closed a majority of the time?To prevent water loss Describe how respiratory gases move along a diffusion gradient in insects1) Respiration in cells uses up oxygen, lowering the concentration at the end of the tracheoles.<div>2) Hence, oxygen diffuses along the concentration gradient along trachea and the tracheoles to the cells. </div><div><br></div><div>THE REVERSE APPLIES FOR CO2 </div> How does mass transport work in the tracheal system?"Rings of muscles within the insects body contract and relax <b><u>(rythmic abdominal movement)</u></b><div><br></div><div>This contraction of muscles in insects can <b><font color=""#ff0000"">squeeze the trachea</font></b>, enabling mass movements of air in and out. </div>" What happens when tracheole ends are filled with water?During major activity:<div><br></div><div>1) Muscle cells <b>respire anaerobically</b> and produce lactic acid </div><div>2) This lowers the water potential of muscle cells</div><div>3) Water moves by osmosis from the tracheoles into the muscle cells</div><div>4) This increases the <b>exposed surface area to air </b></div><div>5) Gases diffuse faster through air than water,<b> so a greater volume of oxygen is supplied</b></div> What are the positive/negative consequences of the tracheole ends filling with water?POSITIVE:<div>Increased rate at which air is moved in the tracheoles</div><div><br></div><div>NEGATIVE:</div><div>Leads to greater water evaporation</div> Contrast the trachea of a mammal and the trachea of an insect (5)1. Mammals have just one trachea whereas insects have multiple tracheae<div>2. Trachea of mammals have a larger diameter</div><div>3. Trachea is made up of cartillage whereas insects tracheae is made up of chitin.</div><div>4. Mammal trachea is longer.</div><div>5. Mammal trachea branch into bronchi whereas insect trachea branch into tracheoles. </div> The cardiac muscle is myogenic. What does myogenic mean?Can contract / relax without receiving electrical impulses from nerves. Where are baroreceptors and chemoreceptors located?In the aorta and carotid arteries What are baroreceptors stimulated by?High / low blood pressure. Which part of the brain modifies heart rate?Medulla oblongata. Which centre of the medulla oblongata increase heart rate?The one linked to the SA node by the sympathetic nervous system. Which centre of the medulla oblongata decreases heart rate?The one that is linked to the SA Node by the parasympathetic nervous system. What are chemoreceptors stimulated by?High / low pH. (High CO<sub>2</sub> conc. lowers blood pH) What are the 5 stages of a response to a stimulus?1. Stimulus<div>2. Receptor</div><div>3. Co-ordinator</div><div>4. Effector</div><div>5. Response.</div> Explain why the diameter of the trunk is smallest at midday using the cohesion-tension theory of water movement through a plant. [6]<ul><li>Diameter of trunk is minimal at warmest time of day</li><li>Stomata are open in light so more water loss</li><li>Water evaporates more when warm as there is more heat energy for evaporation</li><li>H bonding between molecules causes cohesion between water molecules</li><li>Adhesion occurs between water molecules and walls of xylem vessels</li><li>Xylem is pulled inwards by faster flow of water</li></ul> What is kinesis? [3]"<ul><li>Non-directional <b><font color=""#ff1f0f"">random </font></b>response <span style=""color: var(--field-fg); background: var(--field-bg);"">to a non-directional stimulus. </span></li><li><span style=""color: var(--field-fg); background: var(--field-bg);"">The more unpleasant the stimulus, the faster the <b>rate of turning </b>seen in the animal's movement. </span></li><li>Animal is hence more likely to find favourable conditions</li></ul>" What is a tropism?"Growth of part of a plant in response to directional stimulus.<div><br></div><div>They can be positive <font color=""#ff0000"">(growth toward a stimulus)</font></div><div><br></div><div>or negative <font color=""#ff0000"">(grow away from stimulus)</font></div>" What is the difference between how IAA works in plant shoot and roots?"In shoots:<div>IAA<font color=""#ff0000""> promotes</font> cell elongation.</div><div><br></div><div>In roots:</div><div>IAA <font color=""#ff0000"">inihibits</font> cell elongation.</div>" Define population.A group of organisms of the same species, occupying a particular space at a particular time that can potentially interbreed.  Define Community.All the populations of different species living in the same habitat at the same time. What are biotic conditions?Living features of an ecosystem<div><br></div><div>e.g predation, disease, food supply.</div> What is a plagioclimax?When human activities prevent succesion and stop a climax community forming.<div><br></div><div>It is usually used for the conservation of a species (as it prevents them being out competed by a new environment)</div> Explain how a resting potential is established. [5]"<img src=""sodium-potassium-pump-crash-course-v2.gif""><div><ul><li>Na<sup>+</sup>-K<sup>+</sup> pump ATrans <font color=""#ff0000"">3 Na out axon & and 2 K into axon</font></li><li>e<sup>-</sup>tro chem. gradient created</li><li>Neurone membrane <font color=""#ff0000"">more permeable to K<sup>+</sup></font> (open K<sup>+</sup> channels) than Na<sup>+  </sup>(closed channels)</li><li>K<sup>+</sup> move out of axon by facilitated diffusion</li><li>Inside of axon more neg relatively to outside = resting potential</li></ul></div>" Where are the gills located in a fish?Within the body of the fish, behind it's head.  How does the countercurrent flow ensure the maximum rate of gas exchange in fish? MS [3]1. Water and blood flow in opposite directions<div>2. Blood is therefore always passing water that has a higher oxygen concentration</div>3. <b>This will maintain the concentration gradient all the way along the gll lamellae. </b> Suggest why a one-way flow is advantageous to fish<b>Less energy</b> is required because <b>the flow does not have to be reversed. </b><div><br></div><div>This is important as water is dense and difficult to move, so would require a lot of energy to move in a two-way system. </div> Why do aerobic organisms need a constant supply of oxygen?To release energy in the form of ATP during respiration.  What are the lungs supported by?A bony box called the ribcage - the ribs can be moved by the muscles between them.  Recall the structure of the trachea/bronchi. MS [6]"<div>-        wall made of <b>c-shaped</b> cartilage</div> <div>-        cartilage is <b>strong </b>so trachea/bronchi do not collapse</div> <div>-        cartilage is c-shaped to give <b>flexibility</b></div> <div>-        lining made of <b>goblet cells</b> and ciliated epithelial cells</div> <div>-        goblet cells make <b>mucus</b>, which traps pathogens/particles</div> <div>-        ciliated epithelial cells have cilia, which pushes mucus up and out of lungs</div>" Describe the structure of the bronchioles"<div>-        wall made of smooth muscle</div> <div>-        smooth muscle contracts, lumen narrows, bronchiole constricts   (occurs when surrounded by noxious gases – reduces amount reaching alveoli)</div> <div>-        walls made of muscles lined with ciliated epithelial cells</div>" What is the function of alveoli?The alveolar membrane is the gas-exchange surface in humans.  What are the function of goblet cells?secrete mucus to trap pathogens/dirt What is the function of the trachea, bronchi and bronchioles?Transport of air, filtration of air<div><br></div><div>Bronchioles also control the amount of air reaching the alveoli</div> What is found between alveoli?collagen and elastic fibres<div><br></div> Describe how elastic fibres between alveoli facilitate gas exchangeThe elastic fibres allow alveoli to stretch as they fill with air when breathing in.<div><br></div><div>They then spring back during breathing out in order to expel carbon dioxide-rich air. </div> Describe the process of Inspiration (5)1. The <b>external intercostal muscles contract</b>, while the internal intercostal muscles relax<div>2. The <b>ribs are pulled up and out</b>, increasing the volume of the thorax</div><div>3. The <b>diaphragm muscles contract</b> causing it to flatten, which also increases the volume of the thorax</div><div>4. The increased volume fo the thorax results in the <b>reduction of pressure in the lungs</b></div><div>5. Atmospheric pressure is now greater than teh pulmonary pressure, so <b>air is forced into the lungs.</b></div> Explain why expiration is normally a passive process whilst inspiration is an active processInspiration requires ATP for the external intercostal muscles to contract.<div><br></div><div>However, during expiration, the recoil of the elastic tissue in the lungs is the <b>main cause</b> of air being forced out. </div> Why is diffusion of gases between the alveoli and the blood very rapid? (6)1. the <b>capillaries</b> are <b>narrow</b>, hence the <b>red blood cells</b> are <b>slowed</b>, allowing more time for diffusion<div>2. red blood cells are <b>flattened</b> against capillary walls, reducing <b>diffusion</b> <b>distance</b></div><div>3. the walls of both alveoli and capillaries are very thin, hence there's a short diffusion distance</div><div>4. alveoli and pulmonary capillaries have a very large total surface area</div><div>5. ventilation of air in the lungs and circulation of blood maintains a steep concentration gradient</div><div>6. blood flow through the <b>pulmonary capillaries</b> maintain a concentration gradient </div> What's important to note about correlation?Correlation does not mean causation - it may be due to other factors.  What is digestion? MS [2]1. Hydrolysis of;<div>2. Large insoluble substances to smaller soluble substances</div> What is the function of the oesphagus?carries food from the mouth to the stomach What is the ileum?<div><br></div>A long muscular tube in which food is further digested and absorbed into the bloodstream.  What is the function of the large intestine?It absorbs water. What is the rectum?The final section of the intestines where faeces are stored.  What is egestion?The process by which faeces from the rectus is periodically removed via the anuis  What is the pancreas?A large gland situated below the stomach. It produces a secretion called pancreatic juice.  What does the pancreatic juice contain?Proteases, lipases and amylases.  How is starch digested in humans? (6) "<ol> <li>Saliva enters the mouth from the salivary glands, this mixes with food during chewing.</li> <li>Saliva contains salivary amylase, which hydrolyses starch into maltose. Contains mineral salts to maintain pH</li> <li>The food enters the stomach, which is acidic thus denatures the amylase and prevents further hydrolysis</li> <li>The food is then passed into the small intestine, where it mixes with the pancreatic juice</li> <li>This contains pancreatic amylase, which continues the hydrolysis of any remaining starch to maltose. Alkaline salts maintain pH</li> <li>Muscles in the intestine wall push food along the ileum. The epithelia lining produces disaccharidase maltase. Maltase is a <strong>membrane bound disaccharidase.</strong> It hydrolyses maltose into glucose, which can then be absorbed through the small intestine.</li></ol>" What's common about all 3 disaccharidase?They are all membrane-bound.  What are the advantageous properties of villi?(4)1. Increased surface area<div>2. Very thin walled</div><div>4. Well supplied with blood vessels / Blood can carry away absorbed molecules to maintain conc gradient <br></div><div>5. Epithelial cells lining the villi possess microvilli</div> (p 1/2) Describe how tryglycerides are digested (up to the formation of chylomicrons)<div><br></div> Bile salts cause the <b>emulsification</b> into smaller droplets increases the surface area for lipase action<br><br>Lipases <b>hydrolyse</b> the <b>ester</b> <b>bonds</b> in the triglycerides to form fatty acids and monoglycerides.<br><br>There is <b>further</b> emulsification and further hydrolysis of triglycerides forming tiny <b>micelles</b>. Micelles transport the fatty acids and<br>monoglycerides to the <b>epithelial</b> <b>cell</b>.<br><br>Micelles come into contact with the epithelial cell, <b>breakdown</b> and release fatty acids and monoglycerides.<br><br>Fatty acids and monoglycerides cross the cell surface membrane by <b>simple</b> <b>diffusion</b> (because they are<br>non-polar/hydrophobic/lipid soluble molecules)<br><br>Once inside the cell, fatty acids and monoglycerides form triglycerides at the <b>endoplasmic</b> <b>reticulum</b>.<br><br>The triglycerides then combine with proteins, lipoproteins and cholesterol in the golgi body, forming<br><b>chylomicrons</b><br><br> (p2/2) What happens after chylomicrons are formed in the golgi? (4)Chlyomicrons move out of the epithelial cells by <b>exocytosis</b>. <div><br></div><div>They enter <b>lympathic capillaries called lacteals</b> that are found at the centre of each villus. <div><br></div><div>From there, the chylomicrons pass, via the <b>lymphatic</b> vessels, into <b>the blood stream. </b></div><div><b><br></b></div><div>The tryglycerides are <b>hydrolysed by an enzyme</b> in the endothelial cells of blood capillaries from where they diffuse into cells. </div></div> Describe the structure of a cellulose molecule and explain how cellulose is adapted for its function<br>in cells (6 marks) (9 potential points)1. made from β-glucose;<br>2. joined by condensation to form glycosidic bond;<br>3. 1 : 4 link described;<br><b>4. “flipping over” of alternate molecules;<br></b>5. hydrogen bonds linking long straight chains;<br>6. cellulose makes cell walls strong;<br>7. can resist turgor pressure/osmotic pressure;<br><b>8. bond difficult to break;<br></b>9. resists action of enzymes Describe the structure of proteins MS [7]<ul><li>Polymer of amino acids;</li><li>Joined by peptide bonds;</li><li>That are formed by condensation;</li><li>Primary structure is the order of amino acids;</li><li>Secondary structure is folding of polypeptide chain due to hydrogen bonding;</li><li>Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide</li><li>bonds;</li><li>Quaternary structure is two or more polypeptide chains</li></ul> ATP is useful in many biological processes. Explain why (4 marks)1.      Releases energy in small &; easily manageable amounts;<br>2.   Broken down in a one step reaction which makes sure energy is available rapidly<br>3.      Phosphorylates substances to make them more reactive<br>4.      Reformed/made again rapidly Describe the biochemical tests you would use to confirm the presence of lipid, non-reducing<br>sugar and amylase in a sample (5 marks)<b><u>Lipid</u></b><br><br>Add ethanol/alcohol and shake/mix then pour into/add water;<br>2. White/milky emulsion<br><br><b><u>Non-reducing sugar<br></u></b>3. Do Benedict’s test and stays blue/negative;<br>4. Boil with acid then neutralise with alkali;<br><div>5. Heat with Benedict’s and becomes red/orange (precipitate);</div><div><br></div><b><u>Amylase</u></b><br>6. Add biuret (reagent) and becomes purple/violet/mauve/lilac;<br>7. Add starch, (leave for a time), test for reducing sugar/absence of starch; Haemoglobins are chemically similar molecules found in many different species. Differences<br>in the primary structure of haemoglobin molecules can provide evidence of <b>phylogenetic</b><br>(evolutionary) relationships between species. Explain how. (5 marks)1.Mutations change base / nucleotide (sequence);<br>2.(Causing) change in amino acid sequence;<br>3.Mutations build up over time;<br>4.More mutations / more differences (in amino acid/ base / nucleotide sequence / primary<br><div>structure) between distantly related species;</div><div>5. Closely related species have recent common ancestor;</div> Describe the roles of iron ions, sodium ions and phosphate ions in cells (5 marks)<b><u>Iron ions<br></u></b>1. Haemoglobin binds/associates with oxygen<br><br><b><u>Sodium ions<br></u></b>2. Co-transport of glucose/amino acids (into cells);<br>3. (Because) sodium moved out by active transport/Na – K pump;<br>4. Creates a sodium concentration/diffusion gradient;<br><div>5. Affects osmosis/water potential;</div><div><br></div><b><u>Phosphate ions<br></u></b>6. Affects osmosis/water potential;<br>7. Joins nucleotides/in phosphodiester bond/in backbone of DNA/RNA/in nucleotides;<br>8. Used in/to produce ATP;<br>9. Phosphorylates other compounds (usually) making them more reactive;<br>10. Hydrophilic/water soluble part of phospholipid bilayer/membrane; Explain five properties that make water important for organisms (5 marks)<div>1. A <b>metabolite</b> in condensation/hydrolysis/ photosynthesis/respiration;<br>2. A <b>solvent</b> so (metabolic) reactions can occur<br></div><div>3. <b>High</b> <b>heat</b> <b>capacity</b> so buffers changes in temperature;<br></div>4. Large latent heat of vaporisation so provides a cooling effect (through evaporation);<br>5. Cohesion (between water molecules) so supports columns of water (in plants);<br>6. Cohesion (between water molecules) so produces surface tension supporting (small) organisms; Draw and label the structure of a synapse."<img src=""synaptic+transmission.png"">" Draw and label the structure of a neuromuscular junction"<img src=""262-neuromuscular-junction.png"">" Compare transmission across cholinergic synapses compared to neuromuscular junctions MS [5]"<ul><li>neurone to neurone vs neurone to muscle;</li><li><font color=""#ff0000"">action potential in neurone vs no action potential in muscle / sarcolemma;</font></li><li><font color=""#ff0000"">no summation in muscle;</font></li><li>muscle response always excitatory (never inhibitory);</li><li><u>some </u>neuromuscular junctions have different neurotransmitters (noradrenaline as opposed to acetylcholine);</li></ul>" Explain why synapses result in unidirectional nerve impulses. [2]- Neurotransmitter only made in pre-synaptic neurone<div>- Neuro receptors are only on post-synaptic membrane</div> Explain spatial summation of synapses. [3]"- Many presynaptic neurones share the same postsynaptic neurone<div><div>- Collectively release <b>sufficient neurotransmitters </b>to cause <b>sufficient depolarisation </b></div><div>- To reach threshold + trigger AP</div><div><br></div><div><br></div><div><img src=""summation_med.jpeg""><br></div></div>" Explain temporal summation of synapses. Explain why this is important. [3]"<ul><li>1 presynaptic neurone releases neurotransmitter many times over a short period</li><li>Sufficient neurotransmitter to reach threshold to trigger an AP</li><li>Important as low freq APs release insufficient amounts of neurotransmitter to exceed threshold in postsynaptic neurone. Summation allows AP to generate by build up of neurotransmitter.</li></ul><div><img src=""summation_med.jpeg""><font color=""#ff0000""><br></font></div>" Explain inhibition by inihibitory synapses. [3]"<div><ul><li><b><u>Inhibitory neurotransmitters hyperpolarise the postsynaptic membrane.</u></b></li><li>K<sup style="""">+</sup> channels open- K<sup style="""">+</sup> diff out</li><li>Cl<sup>-</sup> open - Cl<sup>-</sup> diff in (makes neurone v.neg compared to outside)</li><li>(inhibits the formation of APs)</li><li>Cannot be depolarised</li><li>Reduces effect of sodium ions entering <b>so much less likely to reach threshold</b></li></ul></div>" Why is skeletal muscle incompressible?So the muscle can transmit force to bone Describe the roles of calcium ions and ATP in the contraction of a myofibril. [7]"<div>1. Ca<sup>2+</sup> diffuse into myofibrils from sarcoplasmic reticulum</div><div><br></div><div>2. Ca<sup>2+</sup>cause movement of tropomyosin</div><div><font color=""#ff0000"">(causes exposure of the binding sites on the actin)</font><br></div><div><br></div><div>4. Myosin heads attach to binding sites on actin</div><div><br></div><div>5. Hydrolysis of ATP on myosin heads causes them to bend;</div><div><br></div><div>6. The bending causing pulling actin molecules;</div><div><br></div><div>7. Attachment of a new ATP molecule to each myosin head causes myosin heads to detach from actin sites</div><div><br></div><div><img src=""AfraidRashFowl-max-1mb.gif""><br></div>" Describe the role of myosin in myofibril contraction [3]<ul><li>Myosin head binds to actin and pulls actin past</li><li>Myosin detaches from actin and resets.</li><li>Using ATP</li></ul> What happens to the H zone, I band, A band and Z lines during muscle contraction? [4]"H zone = shorter<div><br></div><div>I band = shorter</div><div><br></div><div>A band = same</div><div><br></div><div>Z discs = closer together</div><div><img src=""1606648542278.jpg""><br></div>" Explain the importance of maintaining a stable core temperature. [3]"<ul><li>Enzymes work at an <font color=""#ff0000"">optimum </font>temperature</li><li>Too low > not enough K.E > fewer successful collisions</li><li>Too high > enzymes denatures as H bonds in 3<sup>o</sup> break > A.S changes shape + no longer complementary to substrate > fewer e-s complexes</li></ul><div><br></div>" Explain the importance of maintaining stable blood pH [2]- Enzymes working at an optimum pH<div>- Too low/high enzymes denature as ionic bonds in 3<sup>o</sup> > A.S changes shape so no longer complementary to substrate > fewer successful collisions and e-s complexes.</div> Explain the importance of maintaining a stable blood glucose concentration. Consider too high and too low."<font color=""#ff0000"">Too low (hypoglyceamia)</font><div>- Not enough gluc. for respiration so less ATP prod.</div><div>- Atrans cant happen.</div><div><br></div><div><font color=""#ff0000"">Too high (hyperglyceamia)</font></div><div>- Blood has low water potential (+ increased solute)</div><div>- Water lost from tissue to blood via osmosis</div><div>- Kidneys can't absorb all glucose > more water lost in uring causing dehydration.</div>" Expain the concept of negative feedback. [2]<ul><li>Receptors detect levels are too low / high; (effectors respond to counteract change)</li><li>Restores levels to original point; (e.g body temp regulation)</li></ul> Explain the concept of positive feedback. [2]"- Amplifies change from normal level<div>- Advantage- rapidly activate something (e.g blood clots)</div><div><font color=""#ff0000"">- NOT INVOLVED IN HOMEOSTASIS</font></div>" State why homeostasis involves multiple negative feedback mechanisms. [3]"<ul><li><font color=""#ff0000"">Greater degree of control</font> over changes in internal environment</li><li>Controls departures in different directions from original state</li><li>Faster response</li></ul>" What is the circulatory system in mammals described as and what does this mean?It is described as a closed, double circulatory system in which blood is <b>confined to vessels </b>and passes<b> twice through the heart for each complete circuit of the body. </b> Why is a double circulatory system necessary in humans? (2)"<ul> <li>Prevents<b> mixing of oxygenated and deoxygenated blood </b>→ so blood pumped to body is fully saturated with oxygen → efficient delivery of oxygen and glucose for respiration<br><br></li> <li>Blood can be pumped at a<b> higher pressure</b> (after being lower from lungs) → substances taken to and removed from body cells quicker and more efficiently</li></ul>" What are two circuits in the human system?<div>Pulmonary Circulation - deoxygenated blood in the right side of the heart pumped to lungs</div><div><br></div>Systemic Circulation - oxygenated blood in left side of the heart pumped to tissues / organic What are two factors that will make it more likely for an organism to have a circulatory pump?1. Low SA:V ratio<div>2. High metabolism</div> What are the 3 stages of the Cardiac Cycle?Diastole<div>Atrial Systole</div><div>Ventricular Systole </div> Recall Atrial Systole. Atrial Systole is the Contraction of the Atria<div><br></div><div><ul><li>Muscle of the atria wall contracts, forcing any remaining blood into the ventricles</li><li>Blood is only pushed a small distance, hence the atria walls are thin compared to the ventricle walls</li><li>Muscles from the ventricles remained relaxed, allowing them to be filled up with blood </li></ul></div> Recall Ventricular SystoleVentricular Systole - Contraction of the Ventricles<div><br></div><div>1. After a short delay, the walls of the ventricles contract</div><div>2. Delays ensures atria is completely empty before ventricles contract</div><div>3. BP is higher in the ventricles than in the atria, so AV valves shut, preventing backflow</div><div>4. PRessure in the ventricles rise further, forcing open the SL valves and pushing blood into the aorta and pulmonary artery . </div> "<div><b><img src=""SfWH53jO0zsR180AfRT2I9uV0rwBntWiDX6QM1So8iVm8CIeevzgEx8CWXh1F8gsraPxyxMJ35sHIraiKvHhCq6nuPwJysQu0ARSfKfnezVKR8C-w6p.png""></b><br></div><div>Interpret this graph of the CARDIAC CYCLE</div>""A - Ventricle is contracting, SL valve opens<div>B - Ventricle relaxing and elasticity causing volume to increase, reduction of pressure to below that of the aorta, SL valves close</div><div>C - pressure inside ventricle falling below that in the atira, atria contracting producing a small pressure, AV valve opens allowing blood to flow into the ventricle</div><div>D- ventricle contracting again, pressure above that of the atria  making the AV valve close again </div> " What are the 3 types of valves and their features in the heart/circulatory system?"<b>Atrioventricular valves</b> = Between atria and ventricles to prevent backflow of blood when the ventricle contract and have higher pressure than the atria. <div><b><br></b></div><div><b>Semi-lunar valves =</b> In aorta and pulmonary artery to prevent backflow into ventricles when pressure in vessels exceeds that in ventricles. This arises when <b>elastic walls of vessels recoil</b>, increasing the pressure within them and when ventricle walls relax reducing ventricular pressure. </div><div><br></div><div><b>Pocket valves =</b> In veins, ensure that blood flows towards the heart rather than away from it </div>" What is the Cardiac Cycle?The sequence of contraction and relaxation of the heart chambers, and the opening/closing of valves during one heart beat.  Describe and explain how fish maintain a flow of water over their gills. [6]<ul><li>Mouth opens, operculum shuts</li><li>Floor of mouth lowered</li><li>Water enters due to decreased pressure</li><li>Mouth closes, operculum opens</li><li>Floor raised results in increased pressure</li><li>Increased pressure forces water over gills</li></ul> What are the two constituents of tobacco smoke that increase the likelihood of heart disease? <div><br></div><div>Explain each risk factor. (3)  </div>"<b><u>1. Carbon Monoxide</u></b><div><br></div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> Combines with RBC, reducing oxygen-carrying capacity of the blood</div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> Heart has to work harder to supply the equivalent quantiity of oxygen</div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> Leads to raised BP and insufficient oxygen supply to muscles </div><div><br></div><div><b><u>2. Nicotine</u></b></div><div><b><u><br></u></b></div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> stimulates the production of adrenaline</div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> increases heart rate and raises blood pressure (risk: stroke)</div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> makes platelets more sticky, hence form clots (risk: thrombrosis) </div><div> </div><div><br></div>" What are the 2 types of blood cholesterol and their functions?<div><br></div><div>(which one is good, which one is bad?) </div>"1. <font color=""#00ff00"">HDLs </font>- remove cholesterol and trasport it to the liver for excretion<div><br></div><div>2. <font color=""#ff0000"">LDLs </font>- transport cholesterol from the liver to the tissues, including the artery walls, which they infiltrate and leads to the development of atheroma (buildup of plaque) </div>" How does diet affect the risk of cardiovascular disease? (2)1. High levels of salts raise blood pressure<div><br></div><div>2. High levels of saturated fat, increase the concentration of LDLs </div> Arteries, arterioles and veins have a similar <b>layered </b>structure. From the outside inwards, state the layers."OUTERMOST LAYER<div><br></div><div><b>1. Tough fibrous outer layer </b></div><div>    <span style=""color: rgb(32, 33, 36);"">➤</span> resists pressure changes</div><div><b>2. Muscle Layer</b></div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> contracts to control blood flow</div><div><b>3. Elastic Layer </b></div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> stretch + recoil maintains pressure</div><div><b>4. Thin inner lining</b></div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> smooth to reduce friction, thin for diffusion</div><div><b>5. Lumen </b></div><div>   <span style=""color: rgb(32, 33, 36);"">➤</span> central cavity through which blood flows</div><div><br></div><div>INNERMOST LAYER</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div>INNERMOST LAYER</div>" Contrast the structure of arterioles and arteries (2)<br><div>1. Thicker muscle layer than arteries --> contract to <b>control flow of blood</b></div><div><br></div><div>2. Elastic layer is <b>relatively thinner </b>than in arteries --> because blood pressure is lower</div> Vein structure related to functionLow pressure<div><br></div><div>1. <b>Thin </b>muscle layer </div><div>    ➤ carry blood away from tissues hence their constriction and dilation cannot control flow of blood to the tissues</div><div><br></div><div>2. Elastic layer is <b>thin </b></div><div>     ➤ low pressure of blood will not cause them to burst, pressure too low to cause a recoil action</div><div><br></div><div>3. Overall thickness of the wall is <b>small</b></div><div>     ➤ pressure is low, can be flattened easily </div><div><br></div><div>4. <b>Valves </b>at intervals throughout</div><div>    ➤ ensures blood does not flow backwards</div><div>    ➤ ensures blood flow is towards the heart </div> Relate capillary structure related to their function (7)f: exchange metabolic materials<div><br></div><div>a:</div><div><br></div><div>1. Single cell thick walls and flattened endothelial cells</div><div>  ➤ extremely thin, short diffusion pathway</div><div><br></div><div>2. Numerous and highly branched</div><div>   ➤ large surface area for exchange</div><div><br></div><div>3. Narrow diameter</div><div>  ➤ permeate tissues, which means no cell is far from a capillary, <b>short diffusion pathway</b></div><div><br></div><div>4. Lumen is narrow</div><div>   ➤ red blood cells are squeezed flat, hence are in contact with the wall, diffusion pathway shortens</div><div>   ➤ reduces flow rate, increasing diffusion time </div><div><br></div><div>5. Spaces between lining cells</div><div>   ➤ allow white blood cells to escape to escape in order to deal with infections within tissues </div><div><br></div><div>6. Permeable capillary membrane</div><div>    ➤ allows gases to move across the membrane</div><div><br></div><div>7. Fenestrations</div><div>    ➤ allows large molecules to go through</div><div><br></div><div><div><br></div></div> State 2 factors that affect blood glucose concentration."Eating a meal = increases bldgluc conc. <div><font color=""#ff0000"">(glucose absorbed from intenstine to blood)</font><br><div><br></div><div>Exercise / fasting = decrases bldgluc conc.</div></div><div><font color=""#ff0000"">(incr. rate of respiration of glucose)</font></div>" When and where is insulin secreted?"When <font color=""#ff0000"">blood glucose conc. is too high</font><div><br></div><div>Secreted from <font color=""#ff0000"">beta cells in islets of Langerhans</font> in pancreas<br></div>" When and where is glucagon secreted?"Alpha cells in islets of Langerhans in pancreas<div><br></div><div>Secreted when <font color=""#ff0000"">bldgluc conc. is LOW</font></div>" When and how is adrenaline secreted?"Secreted by <font color=""#ff0000"">adrenal glands</font> when bldgluc conc. is low / stressed<div><br></div><div><br></div>" How do adrenaline and glucagon demonstrate a secondary messenger model?They're the first messengers.<div>They cause glycogenolysis to occur inside the cells even though they bind to receptors on the outside of the cell.</div> Why does diet low in protein cause accumulation of tissue fluid?<div><br></div><div>1. less protein in the blood, hence higher water potential</div><div>2. water potential gradient is lower, </div><div>3. less tissue fluid can return</div> Explain how the structure of DNA is related to its functions (6 marks)1.      <b>Sugar</b>-<b>phosphate </b>(backbone) is double stranded into a helix so provides strength &amp;<br>stability (protects bases);<br>2.      <b>Long </b>/ <b>large </b>molecule so can store lots of information;<br>3.      <b>Helix </b>/ coiled so <b>compact</b>;<br>4.      <b>Base sequence </b>allows information to be stored (protein formation);<br>5.      <b>Double stranded </b>so replication can occur semi-conservatively as existing<br>strands can act as templates via complementary base pairing<br>6.      <b>Weak hydrogen bonds </b>for replication and strand separation OR many<br>hydrogen bonds so stable/strong; Describe and explain how the structure of DNA results in accurate replication (4 marks)1       Two strands therefore semi-conservative replication;<br>2       base pairing held together by hydrogen bonds<br>3       hydrogen bonds weak so easily broken, which allows strands to separate;<br>4       bases exposed and act as a template;<br>5       A with T, C with G;<br>6       DNA made has one parent strand and one new strand Explain how a mutation can result in the production of a non-functional protein receptor (4<br>marks)1.      Change in <b>DNA </b>base sequence;<br>2.    Change in amino acid sequence;<br>3.    This alters position of hydrogen/ionic/disulfide bonds;<br>4.    And causes a change in the <b>tertiary </b>structure (of receptor); "Which bases are purine and which are pyrimidine?"<b>A & G</b> = 2-ring purine bases<div><br></div><div><b> T & C & U</b> = 1-ring pyrimidine bases</div> ATP is described as...a nucleotide derivative of adenine with 3 phosphate gorups  Outline how colorimetry could be used to determine the concentration of sugars in a sample using a calibration curve<div><br></div>1. Make standard solutions with <b>known concentrations</b>. Place this in a colorimeter and record absorbance.<div>2. Plot calibration curve, absorbance on y-axis and concentration on x-axis</div><div>3. Record absorbance of unkown samples, read off conc from curve. </div> How many amino acids are there and how do they differ from one another?20 <div>differ only be side ''R'' group</div> Recall the function and 3 properties of globular proteins. <div><ul><li>Functional</li><li>Compact</li><li>Water soluble</li><li>Metabolic processes</li></ul></div> Recall function and 2 properties of fibrous proteins. <div><ul><li>Function: Structural</li><li>Insoluble in water</li><li>Form long chains</li></ul></div> State the formula for pHpH = -log10[H+]  Why is it easier for subsequent oxygens to bind to haemoglobin?➤ The binding of the first oxygen molecule changes the quaternary structure of the molecule, causing it to change shape.<div>➤ This change makes it easier for the subsequent units to bind.<br></div><div>➤ It therefore takes a smaller increase in the partial pressure of oxygen to bind the second molecule<br></div><div>➤ This is known as positive cooperativity / co-operative bonding  </div> Why is it difficult for the last oxygen to bind to haemoglobin, despite positive co-operativity?Majority of the binding sites are occupised, therefore it is less likely that a single oxygen molecule will find an empty site to bind to.  There are many different oxygen dissociation curves depending on the conditions. What are the two facts to remember?1. The further left the curve is, the greater the affinity for oxygen.<div>    ➤loads oxygen readily</div><div>    ➤unloads less easily</div><div><div>2. The further right the curve is, the lower the affinity for oxygen. </div></div><div>    ➤loads oxygen less readily</div><div>    ➤unloads it more easily </div> Draw the oxygen dissociation curve, for different CO2 concentrations. 2kPa 5kPa 8kPa"<img src=""paste-6d38a2e3365d59579e4c0c5fa6f7b8021c396e69.jpg"">" Why does the presence of CO2 affect the affinity of haemoglobin?"➤ Dissolved CO<sub style="""">2</sub> is acidic, the low pH causes haemoglobin to change shape such that it has a lower affinity for oxygen. <div>➤ This is because H+ ions will bind to the haemoglobin, causing a conformational change to it's shape, resulting in a shape that will release oxygen more readily. <span style=""color: rgb(32, 33, 36);""><br></span></div>" What is altitude sickness?"<span style=""color: rgb(32, 33, 36);"">➤ </span>Caused by acute exposure to low partial pressure of<br>oxygen at high altitude<br><br><span style=""color: rgb(32, 33, 36);"">➤ </span>Compensated by altitude acclimatisation – body<br>combats it by producing more red blood cells." What is myoglobin?A red pigment in mammlian muscles. Has a higher affinity for O2 than Hb, only releasing it a very low partial pressure. It ''stores'' oxygen.  Foetal haemoglobin is different to adult haemoglobin. Explain how and why. "➤ Higher affinity for oxygen<div>➤ This means maternal haemoglobin will dissociate itself in the placenta and the foetal haemoglobin will load with oxygen<br></div><div>➤ This ensures the foetus receives a sufficient supply oxoygen <span style=""color: rgb(32, 33, 36);""><br></span></div>" Where is glycogen found?found as small granules in the muscles and liver of animals  Relate the structure of tryglycerides to their properties (4)"➤ <b style="""">source of energy</b> - high ratio of energy storing C-H bonds to C atoms<div>➤ <b>storage </b>- low mass to energy ratio; much energy in a small volume<br></div><div>➤ <b>insoluble </b>in water - large, non polar molecules dont affect water potential<b><br></b></div><div>➤ <b style="""">water source </b>- high ratio of H to O atoms, release water when oxidised <span style=""color: rgb(32, 33, 36);""><br></span></div>" What control can we carry out for the emulsion test?Repeat with water instead of sample, solution should remain clear.  Describe the cohesion-tension theory of water transport in the xylem [6] MS"<b><span style=""font-weight: 400;"">1. water </span><span style=""font-weight: 400; text-decoration-line: underline;"">evaporates / transpires</span><span style=""font-weight: 400;""> from leaves;</span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;"">2. reduces water potential in cell;</span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;"">3. water is drawn out of xylem;</span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;"">4. creates tension;</span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;"">5. cohesive forces between water molecules due to hydrogen bonds;</span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;""><br></span><span style=""font-weight: 400;"">6. water pulled up as a continuous, unbroken column;</span></b>" 6.4 - What are the key properties of leaves? (6)<b>1. thin</b><div>    ➤ short diffusion pathway</div><div><b>2. large SA:V ratio</b></div><div>    ➤ absorb more sunlight</div><div><b>3. arranged in a manner that prevents overlapping</b></div><div>    ➤ prevents shadow forming on the surface</div><div><b>4. stomata on it's surface</b></div><div>    ➤ allow gases to enter/exit the leaf</div><div><b>5. numerous air spaces</b></div><div>    ➤ within which gases can be exchanged</div><div><b>6. large network of xylem and phloem</b></div><div>   ➤ xylem to transport water</div><div>   ➤ phloem to transport sugars formed in photosynthesis</div> Explain the adaptations of plants that facilitate <b>gaseous exchange </b>[4]<ul><li>Many stomata; short diffusion pathway</li><li>Air spaces; increased contact</li><li>Large SA; of mesophyll cells</li><li>Diffusion Distances Small; single cell wall on mesophyll</li></ul> 6.4 - What is the problem with stomata? How can this be overcome?  [4] <div><ul><li>water is lost from gas exchange surface</li><li>from wet cell walls of mesophyll tissue</li><li>hence stomata remain closed</li><li>achieved through guard cells</li></ul></div> What are the adaptations of xerophytes to prevent water loss? MS [6]1. Hairs so 'trap' water vapour and water potential gradient decreased;<div>2. Stomata in pits so 'trap' water vapour and water potential gradient decreased;</div><div>3. Thick waxy layer so increases diffusion distances</div><div>4. Waxy layer/cuticle so reduces evaporation</div><div>5. Rolled leaves so 'trap' water vapour and water potential gradient decreased</div><div>6. Spines/needles so reduced SA:V ratio </div> Sketch and label the vertical section through a dicotyledonous leaf, showing gas exchange whne photosynthesis is taking place"<img src=""paste-8a00dcb45ff280aecf5578c1293958833b0c5224.jpg"">" 6.4 - Describe how guard cells work (5)"➤ guard cells actively pump in K+ ions<div>➤ reduces ψ<br></div><div>➤ water enters by osmosis down a water potential gradient</div><div>➤ guard cells become turgid<br></div><div>➤ stomata pore opens<span style=""color: rgb(41, 41, 41);""><br></span></div>" How long do diastole/systole last?Diastole - 0.5 seconds<div><br></div><div>Systole - 0.3 seconds</div> Give the properties of glycogen. [4]<ul><li>Insoluble → doesn't affect ψ</li><li>Large → cannot leave cells</li><li>Compact → stored in small spaces</li><li>Highly branched → larger surface area for enzymes to act on</li></ul> When investigating the effect of enzyme concentration on a reaction, what factors must we keep constant? (3)1. Temperature of the <b>solution</b><div>2. pH of the <b>solution </b></div><div>3. Concentration of Substrate</div> Explain the advantages of lipid droplet and micelle formation. [3]<ul><li>Droplets increase SA for lipase</li><li>So faster hydrolysis</li><li>Micelles carry fatty acids and glycerol through membrane</li></ul> Describe how bacteria divide. [4]<ul><li>Binary fission</li><li>Replication of circular DNA</li><li>Division of cytoplasm to produce 2 daughter cells</li><li>Each with a single copy of circular DNA</li></ul> Explain how cells lining the ileum of mammals absorb glucose by co-transport with Na<sup>+</sup> ions. [3]• Na<sup>+</sup> actively transported from ileum cell to blood<div>• Maintains diffusion grad for Na<sup>+</sup> to enter cells from gut</div><div>• Glucose enters by facilitated diffusion with Na<sup>+</sup></div> Suggest and explain why the combined action of endopeptidases and exopeptidases are more efficient than exopeptidases on their own. [2]<ul><li>Endopeptidases hydrolyse internal peptide bonds</li><li>More ends for exopeptidases</li></ul> Suggest the advantage of producing trypsin in an inactive form inside cells of the pancreas. [2]<ul><li>Does not digest protein inside cells</li><li>So pancreatic cell isn't damaged</li></ul> Explain why maltase can only catalyse the hydrolysis of maltose. [3]<ul><li>Active site of enzyme has specific shape</li><li>Only maltose can bind</li><li>To form E-S complex</li></ul> Explain why binding of one molecule of O<sub>2</sub> to Hb makes it easier for a second O<sub>2</sub> molecule to bind. [2]<ul><li>Binding of first O<sub>2</sub> changes 3° structure of Hb</li><li>Uncovers second binding site</li></ul> Explain 6 ways in which the structure of the aorta is related to its function. [6]<ul><li>Elastic tissue maintains pressure</li><li>Elastic tissue stretches when ventricle contracts and recoils when ventricle relaxes</li><li>Muscle for contraction</li><li>Thick wall withstands pressure</li><li>Smooth endothelium reduces friction</li><li>SL valve prevents backflow</li></ul>  Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta. (5 marks)"<div>1.      Atrium has higher pressure than ventricle due to filling / contraction. This causes the atrioventricular valves to open;</div> <div>2.      Ventricle now has higher pressure than atrium (due to filling / contraction). This causes atrioventricular valves to close;</div> <div>3.      Ventricle has higher pressure than aorta causing semilunar valve to open;</div> <div>4.     This leads to a higher pressure in the aorta than the ventricle (as heart relaxes) causing semilunar valve to close;</div> <div>5.     (Muscle / atrial / ventricular) contraction causes increase in pressure;<b></b></div>" "Explain how tissue fluid is formed and how it may be returned to the circulatory system. (6 marks)""<div>1.     Hydrostatic pressure of blood is high at arterial end;</div> <div>2.     Fluid & soluble molecules pass out;</div> <div>3.     Proteins & large molecules remain behind;</div> <div>4.     This lowers the water potential;</div> <div>5.     Water moves back into venous end of capillary by osmosis;</div> <div>6.     Lymph system collects any excess tissue fluid which returns to blood and returns this tissue fluid to the veins;</div><div><br></div><div>(my own points)</div><div><ul><li>hydrostatic pressure reduced due to loss of fluid</li><li>forces smaller molecules back in</li></ul></div>" "Explain how the ventilation mechanism of a fish and the structure of its gills result in the efficient uptake of oxygen from water (6 marks)""<img src=""paste-b70a6d89350023c61cdfb9b4e97e2da09fa18c6a.jpg"">" "<div>Describe and explain how the structure of the mammalian breathing system enables</div> <div>efficient uptake of oxygen into the blood. MS [9]</div>""<div> </div> <div><b>1. Alveoli provide a large surface area;</b></div> <div>2. Walls of alveoli thin to provide a short diffusion pathway;</div> <div>3. Walls of capillary are thin between the alveoli so provides a short diffusion pathway;</div> <div>4. Walls of capillaries/alveoli have flattened cells;</div> <div>5. Cell membrane permeable to gases;</div> <div><b>6. Many blood capillaries provide a large surface area;</b></div> <div>7. Intercostal muscles & diaphragm muscles used to ventilate lungs to maintain a diffusion gradient;</div> <div>8. Wide trachea & branching of bronchi/bronchioles for efficient flow of air;</div> <div><b>9. Cartilage rings used to keep airways open</b></div>" "<div>Describe the gross structure of the human gas exchange system and how we breathe in and out. (6)</div>""<img src=""paste-cd020a39bcf63eb6f10839fc5ffa0f3fd3991a71.jpg"">" Describe the induced fit model of enzyme action. MS [3]"<span style=""color: rgb(34, 34, 34);"">· </span>        Active site of enzyme is not <u>complementary</u>;<div>·         Active site is flexible & can mould around the substrate;</div><div>·         Change in enzyme allows substrate to fit and form an E-S complex</div>" "<div>Explain why maltase:</div> <div>•        only breaks down maltose</div> •        allows this reaction to take place at normal body temperature. (5 marks""<div>1.     Specific <u>Tertiary</u> structure enzyme (means)</div> <div>2.      Active site is only complementary to maltose</div> <div>3.      Description of induced fit;</div> <div>4.      Enzyme is a catalyst which lowers the activation energy required for the reaction</div> <div>5.      By forming an enzyme-substrate complex;</div>" <div>Describe competitive and non-competitive inhibition of enzymes. MS [7]</div>"<div>1.      Inhibitors reduce binding of enzyme to substrate & prevent the formation of E-S complexes</div> <div><b>(Competitive inhibition),</b></div> <div>2.      Inhibitor has a similar shape to substrate;</div> <div>3.      It binds to the active site (of enzyme);</div> <div>4.     Inhibition can be overcome by adding more substrate;</div> <div><b>(Non-competitive inhibition),</b></div> <div>5.      Inhibitor binds to a site on enzyme other than active site;</div> <div>6.      This changes the shape of the active site</div> <div>                  7.     Inhibition cannot be overcome by adding more substrate</div>" "<div>Describe the role of the enzymes of the digestive system in the complete breakdown of starch (5 marks)</div>""<div>1. Amylase (mouth);</div> <div>2. Breaks down starch to maltose:</div> <div>3. Maltase (Small Intestine);</div> <div>4. Breaks down maltose to glucose;</div> <div>5. Hydrolysis of starch involves breaking;</div> <div>6. Of glycosidic bond</div>" "<div>Describe the processes involved in the absorption of the products of starch digestion (5 marks)</div>""<div>·         Sodium removed from epithelial cell by active transport/sodium- potassium pump;</div> <div>·         Into blood;</div> <div>·         Maintaining low concentration of sodium in the epithelial cell compared to the lumen;</div> <div>·         Glucose moves in to the epithelial cell with sodium </div> <div>·         Via carrier/channel protein</div> <div>·         Glucose moves into blood;</div> <div>·         By (facilitated) diffusion</div>" "<div>Describe how proteins are digested in the human gut [4] MS</div>""<div>1.      Hydrolysis of peptide bonds;</div> <div>2.      Endopeptidases break polypeptides into smaller peptide chains;</div> <div>3.      Exopeptidases remove terminal amino acids;</div> 4.      Dipeptidases hydrolyse dipeptides into amino acids" The epithelial cells that line the small intestine are adapted for the absorption of glucose. Explain how. (6 marks)<div>1.      Microvilli provide a large surface area;</div><div>2.      Many mitochondria produce ATP for active transport;</div><div>3.      Carrier proteins present for active transport;</div><div>4.      Channel / carrier proteins for facilitated diffusion;</div><div>5.      <u>Co-transport</u> of sodium and glucose achieved through carrier protein for sodium (ions) and glucose;</div><div>6.      Membrane-bound enzymes digest disaccharides to produce glucose;</div> Explain how the structure of xylem tissue is adapted to its function MS [4]<ul><li>long cells / tubes with no end walls; continuous water columns;</li><li>no cytoplasm / no organelles / named organelle; to impede / obstruct flow / allows easier water flow;</li><li>thickening / lignin; support / withstand tension / waterproof / keeps water in cells;</li><li>pits in walls; allow lateral movement / get round blocked vessels;</li></ul> 7.7 - What's the evidence for the cohesion-tension theory?<b>Change in tree trunk diamete</b>r → transpiration greatest during the day, higher tension causes shrinkage<div><br></div><div><b>If a xylem is broken, air enters</b> → breaks continous water column (cohesion) hence water is no longer drawn up</div><div><br></div><div><b>Water doesn't leak from a broken xylem vessel</b> → due to the tension within it</div> What kind of process is transpiration?Transpiration is a passive process as it requires no metabolic energy; it uses solar energy from the sun.  Describe the roles of centromeres. [3]<ul><li>Holds chromatids together</li><li>Attaches chromatids to spindle</li><li>Allows chromatids to move to opposite poles</li></ul> Give 4 reasons why mitosis is important in the life of an organism. [4]<ul><li>Growth in cell number</li><li>Replace cells</li><li>Genetically identical cells</li><li>Asexual reproduction</li></ul> What substance is the waxy cuticle made up of?A lipid called suberin   7.7 - Explain why less water is lost through the upper surface of leaves than is lost through the lower surface (2)1. more stomata on the lower surface<div>2. thicker waxy cuticle on the upper surface </div> 7.7 - What are the 4 external factors affecting transpiration?<b>1. Light</b> ➜ stomata open in the light and close in the dark ∝<div><b>2. Temperature</b> ➜ alters the kinetic energy of the water molecules and the relative humidity of the air  ∝</div><div><b>3. Humidity</b> ➜ affects the water potential gradient  1/∝</div><div><b>4. Air movement</b> ➜ alters the rate at which moist air is removed from around the leaf  ∝</div> 7.7 - What are the 4 internal factors that affect the rate of transpiration?1. <b>Number of leaves</b> ➜ more; bigger surface area; more stomata for gaseous exchange<div>2.<b> Number of stomata</b> ➜ more stomata; more pores for transpiration</div><div>3.<b> Size of the leaf</b> ➜ bigger surface area</div><div>4. <b>Precense of a plant cuticle</b> ➜ waxy cuticle is impermeable to water; reduces evaporation </div> What measurements should you take on a potometer to calculate the rate of water uptake?1. Diameter of the tube to calculate volume<div>2. Distance moved by the bubble</div><div>3. Time </div> 7.7 - Why is the leafy shoot in a potometer cut under water rather than in the air / why are the joints sealed with water proof jelly? Prevents air entering, which would break the continuous water column Give 4 reasons why the potometer does not truly measure the rate of transpiration MS [4]Water used for support / turgidity;<br><br>Water used in photosynthesis;<br><br>Water produced in respiration;<br><br>Apparatus not sealed / ‘leaks’ 7.7 - Suggest how the reservoir in a potometer allows repeat measurements to be madeReturns bubble (to start); 7.7 - What assumption must be made if a potometer is<br>used to measure the rate of transpiration?All water taken up is used in transpiration  7.7 - In a potometer, how do we use the reservoir to reset the bubble?The tap is opened and the syringe is pushed down  7.8 - Give examples of the sources / sinks in leaves "<div><strong>Source</strong> → photosynthesizing cells within leaves</div><div><br></div> <div><strong>Sink</strong> → sinks are growing regions (meristems), storage organs or seeds.</div>" "7.8 - During translocation, transport can happen in <span class=""cloze"" data-cloze=""any direction"" data-ordinal=""1"">[...]</span>""7.8 - During translocation, transport can happen in <span class=""cloze"" data-ordinal=""1"">any direction</span><br> " Describe the mass-flow hypothesis for the transport of sugars in the plant stem [6] MS"<div> 1.      At source sucrose is actively transported into the phloem/sieve tube;</div> <div>2.      By companion cells;</div> <div>3.      Lowers water potential in phloem/sieve element/tube <b>and</b> water enters by <u>osmosis</u>;</div> <div>4.      This produces a high hydrostatic pressure;</div> <div>5.      <u>Mass</u> flow/transport towards sink/roots/storage tissue occurs;</div> <div>6.      At sink/roots sugars are removed/unloaded;</div>" Recall the Mass Flow Theory. MS [7]"1. <b>Facilitated diffusion</b> moves sucrose from photosynthesising cell into companion cells<div><br><div>2.<b> Co-transport</b> with hydrogen ions being<b> actively transported </b>loads sucrose into phloem sieve tubes, lowering water potential at the source end of the phloem.</div><div><br></div><div>3. Water enters tubes by osmosis from <b>xylem</b>, creating a <b>high hydrostatic pressure </b>at the source end</div><div><br></div><div>4. Mass flow/transport towards the sink</div><div><br></div><div>5. Sucrose <b>actively transported by companion cells into sink</b> for respiration or storage as starch</div><div><br></div><div>6. <b>Increases water potentia</b>l in sieve tubes, water leaves by osmosis which lowers pressure</div><div><br></div><div>7. Resultant hydrostatic pressure gradient, so there is continuous mass flow </div><div><br></div><div><img src=""active-translocation_med.jpeg""><br></div></div>" Describe ringing experiments"1. rings of bark and phloem removed<div>2. swelling above ring due to sugar accumulation </div><div>3. reduced growth below ring </div><div><b><br>Conclusion</b>: When you remove the phloem from the stem, it interrupts the flow of sugar to regions below the removed ring (causing eventual death). Hence, the phloem is responsible for translocating sugars.<br></div><div><br></div><div><img src=""Untitled.png""></div><div><br></div>" State the evidence for the mass flow hypothesis<div><br></div>1. Pressure in sieve tubes; sap released when cut<div>2. Sucrose conc. higher in leaves than roots</div><div>3. Downward flow occurs in daylight only (photosynthesis occurs)</div><div>4. Companion cells have mitochondria for ATP production</div> 7.8 - State the evidence against the mass flow hypothesis (3) 1. Function sieve plates unclear as they hinder mass flow<div>2. Not all solutes move at the same speed</div><div>3. Sucrose delivered at the same rate, independent of concentration gradient</div> State 2 things unspecialised cells are capable of."- <font color=""#ff0000"">Self renewal</font> (can divide to replace themselves)<div><br></div><div>- <font color=""#ff0000"">Specialisation / differentiation</font> (can develop into other types of cell)</div>" Explain how stem cells specialise. [4]1. Stimulus (e.g chemical)<div><br></div><div>2. Causes selective activation of genes (e.g muscle cells gene coding for actin and myosin need to be acitvated)</div><div><br></div><div>3. mRNA only transcribed from active genes => translated on ribosomes = proteins</div><div><br></div><div>4. These proteins modify cell permanently and determine cell structure / function</div> State 3 ways stem cells are used in medicine."<ul><li><font color=""#ff0000"">Regrow </font>damaged tissues in accidents or by disease e.g B cells in the pancreas in type 1 diabetes</li><li>Drug testing (used to grow artificial tissues)</li><li>Developmental biology research (provides insight into embryo development)</li></ul>" Explain how iPS are produced [3]"- Produced from <font color=""#ff0000"">adult somatic cells</font><div><br></div><div>- Specific <font color=""#ff0000"">protein transcription factors</font> associated with pluripotency put into cells, causing cells to express genes associated with pluripotency</div><div><br></div><div>- Cells <font color=""#ff0000"">cultured</font></div>" State 2 advantages of using iPS in medical treatment.- No immune rejection as can be made using patient's own cells<div><br></div><div>- Overcome some ethical issues with using embryonic stem cells (no embryo destroyed)</div> 5.1 - What are the 2 types of responses involving lymphocytes?Cell mediated response, involving T lymphocytes<div><br></div><div>Humoral response, involving B lymphocytes</div> 5.1 - What 4 things do antigens allow the immune system to identify?pathogens<div>non-self material</div><div>toxins</div><div>abnormal body cells </div> 5.1 - A variety of molecules are present on a foreign cells surface. Why is it that the proteins are the most important?Highly specific tertiary structure<div>Enormous variety</div><div>Allows the immune system to distinguish one cell from another</div> 5.1 - In what cases is an immune response disadvantageous?<div><br></div>In organ transplants, immune system recognises these as non-self and attempts to destroy the transplant. 5.1 - How do doctors minimise the risk of organ rejection?Tissue type is matched<div>Immunosuppressants are used </div> 5.1 - Summary diagram of defense mechanisms (figure 2) "<img src=""paste-3d9c5f4fe0cc26b6561485fd3946097fb27940eb.jpg"">" 5.1 - How is it that lymphocytes recognise cells belonging to the body?In the fetus, different lymphocytes are colliding with other cells. Those that fit the body's own cells die or are supressed. <div>Only remaining lymphocytes are those that may fit foreign material. </div><div><br></div><div>In an adult, lymphocytes produced in the bone marrow initially only encounter self-antigens - these cells undergo apoptosis. Only lymphocytes that might respond to non-self-antigens are left in the blood. </div> 5.2 - If physical barriers fail, what is the next line of defence in an organism?Phagocytosis 5.2 - What are the two types of white blood cells?1) Phagocytes (including neutrophils and macrophages)<br>2) Lymphocytes (including T &amp; B lymphocytes and Memory Cells) What is an antigen? MS [2]<u>Foreign </u>protein;<div>that <u>stimulates </u>an <u>immune response</u></div> 5.2 - Why is phagocytosis necessary?At the end of phagocytosis, phagocytes present antigens on their cell surface membrane. These foreign antigens are recognised by T-cells and initiate the specific immune response.  5.3 - Define immunityThe ability of an organism to resist infection by protecting against disease-causing microorganisms or their toxins that invade the body  5.3 - B-cells are said to be involved in ''humoral'' immunity. What does this mean?Immunity involving antibodies that arepresent in body fluids or ''humour'' such as blood plasma  5.3 - Where do T-lymphocytes mature?Thymus gland  5.3 - State 4 features of memory cells (both B and T)Circulate in the blood<div>Provide an immunological memory</div><div>Present <b>after </b>an immune response</div><div>Speed up response to another infections by the same pathogen </div> 5.3 - Why can T cells distinguish invader cells from normal cells?<div><ul><li>transplanted cells have different antigens</li><li>virally infected cells present some of the viral antigens on their membrane</li><li>phagocytes present some of the digested pathogen one their membranes</li><li>cancer cells are different from healthy cells and hence have different antigens</li></ul></div> 5.3 - What is the key drawback of a T-cell?can only respond to antigens presented on a body cell, not to antigens within a bodily fluid  5.3 - What are the types of T cell?Helper T cells<div>Cytotoxic T cells</div><div><br></div> 5.3 - State the stages of the cell-mediated response by T cells (1/2)<li>Pathogens invade body cells or are taken in by phagocytosis</li><li>Phagocyte present antigens from the pathogen on their CSM</li><li>Receptors on a <u>specific </u>T-helper cell fit exactly onto these antigen</li><li>T cell is activated now, and divides rapidly by mitosis and forms clones of <u>genetically identical</u> cells</li><li>These cloned cells can go on to respond to the pathogen in different ways </li> 5.3 - Describe how cloned T cells can respond to a foreign pathogen (2/2)- They can <b>stimulate more phagocytes</b> to start doing phagocytosis<br><br>- They can <b>develop into memory cells</b> that would enable a quicker<br>response for any secondary infections by the same pathogen<br><br>- They can <b>stimulate B cells</b> to multiply and secrete antibodies (humoral<br>response)<br><br>- They can <b>activate cytotoxic T cells</b> 5.3 - How do cytotoxic cells kill infected cells?producing a protein called perforin that makes holes in the CSM 5.3 - Why are T cells more effective against viral infections?viruses exist inside host cells, T cells eradicate the entire host cell, ensuring virus cannot continue to multiply  5.4 - Where do B cells mature?Bone marrow<div><br></div> "5.4 - <span class=""cloze"" data-cloze=""Humoral"" data-ordinal=""2"">[...]</span> immunity uses specific <span class=""cloze-inactive"" data-ordinal=""1"">antibodies</span> to combat infection""5.4 - <span class=""cloze"" data-ordinal=""2"">Humoral</span> immunity uses specific <span class=""cloze-inactive"" data-ordinal=""1"">antibodies</span> to combat infection<br> " "5.4 - <span class=""cloze-inactive"" data-ordinal=""2"">Humoral</span> immunity uses specific <span class=""cloze"" data-cloze=""antibodies"" data-ordinal=""1"">[...]</span> to combat infection""5.4 - <span class=""cloze-inactive"" data-ordinal=""2"">Humoral</span> immunity uses specific <span class=""cloze"" data-ordinal=""1"">antibodies</span> to combat infection<br> " 5.4 - Describe the steps in the humoral response<li>Surface antigens of pathogens taken in by B cell </li><li>B cells present antigens on its surface</li><li>T helper cells attached to processed antigen + activates B cell</li><li>B cells divide via mitosis to produce plasma cells</li><li>Plasma cells produce and secrete specific antibodies that are complementary to the antigen</li><li>Some B cells develop into memory cells → circulate the blood, secondary response</li> 5.4 - State adaptations of a stimulated B cell<li>mitochondria provide (more) ATP / energy;</li><li>(more) RER / ribosomes synthesise proteins;</li><li>(more) Golgi body secretes / modifies or packages proteins /<br>produces glycoproteins;</li><li>(B lymphocytes) produces antibodies;<br></li> 5.4 - Describe the secondary immune response<li>Second exposure to the same pathogen -> a lot quicker</li><li>Memory cells in blood divide to form a large population of B cells </li><li>Produce clones that can make antibodies</li> 5.4 - In what cases may reinfection of the same pathogen occur?<li>Different strains of the same pathogens</li><li>Different antigen (antigenic variability)</li><li>Memory cells aren't useful, produce an incorrectly shaped antibody</li><li>Primary immune response initiated = reinfection </li> 5.4 - B Cells can mature into 2 types of cells. State their names and functions.Plasma cells → secrete antibodies into blood plasma<div><br></div><div>Memory cells → responssible for secondary immune response </div> Recall the features of the genetic code [6]<b>Degenerate code</b> → most AAs coded for by more than 1 triplet<br><b>One direction </b>→ triplets always read in one direction<br><b>Start triplet</b> → always the same; codes for methionine (removed later if it doesn’t form part<br>of the final polypeptide)<br><b>Stop codes</b> → 3 triplets don’t code for any AAs + mark the end of a polypeptide chain<br><b>Non-overlapping</b> → each base only read once<br><b>Universal </b>→ each triplet codes for the same AA in all organisms (few minor exceptions); indirect evidence for evolution 8.2 - What is chromatid?one of the two strands of a chromosome that are joined togehter by a single centromere prior to the division  8.2 - What are homologous chromosomes? A pair of chromosomes that carry the same genes, but not necessarily the same alleles of the genes.  8.2 - If two genes are on the same gene loci...they determine the same features 8.2 - What is a mutation and why are they dangerous?<li>Change in the base sequence of a gene to produce a new allele</li><li>Results in a new AA sequence</li><li>Different polypeptide produced; different protein that may not function properly </li> 8.2 - What is the function of introns?<ul><li>Regulate gene expression</li></ul> What are minisatellites?Repeating sequences of bases in introns What is the proteome of a cell? [1]The full range of proteins that a cell is able to produce at a given time What is the name of the enzyme responsible for splicing?Spliceosome Explain why cancer treatments based on immunological methods<br>are more likely to minimise damage to healthy tissue. (5 marks)<ul><li>Proteins on cell surface membrane of cancer cells;</li><li>different from healthy cells (abnormal);</li><li>abnormal cell surface proteins are non-self antigens;</li><li>immunotherapy facilitates immune system by detecting non-self-proteins;</li><li>immune system mounts immune response; destroys cancer cells</li></ul> 3.8 - Cancer is often described as the result of the cell cycle<br>“being out of control”. Explain this statement. <ul><li>Cell cycle describes the formation of new cells from old cells</li><li>Checkpoints regulate the progression of the cell replication</li><li>Genes control these checkpoints</li><li>Mutation of genes</li><li>Control is lost</li><li>Cancer develops / uncontrolled cell cycle/mitosis</li></ul> Explain how transcription factors work [4]"- Transcription factors are <font color=""#ff0000"">proteins</font><div><br></div><div>- TF moves from <font color=""#ff0000"">cytoplasm => nucleus</font></div><div><br></div><div>- Bind to specific DNA base on <font color=""#ff0000"">promotor region</font></div><div><br></div><div>- Stimulate / Inhibit the <font color=""#ff0000"">transcription of mRNA</font> of target gene by helping / preventing binding of RNA polymerase</div>" Explain the role of oestrogen in initiating transcription. [5]"<ul><li>Oestrogen (steroid hormone) can diff across the PL bilayer as its lipid soluble</li><li>In cytoplasm, oestrogen binds to a receptor of an inactive transcription factor, <font color=""#ff0000"">forms hormone receptor complex.</font></li><li>Inactive transcription factor changes shape, <font color=""#ff0000"">resulting in an active TF.</font></li><li>TF diff from cytoplasm => nucleus and binds to specific DNA base seq on <font color=""#ff0000"">promotor region</font></li><li><font color=""#ff0000"">Stimulates transcription of genes by helping RNA Polymerase bind</font>.</li></ul>" What is a nucleosome? How do they affect transcription?DNA wrapped around histone proteins.<div><br></div><div>How closely the DNA and HP are packed together affects transcription.</div> Explain how increased Methylation of DNA can cause epigenetic changes and its effects. [3]<ul><li>Methyl groups added to cytosine bases in DNA</li><li>Nucleosomes pack more tightly together, preventing transcription factors binding (genes not transcribed)</li><li>It is reversible.</li></ul> Explain how decreased acetylation of associated histones causes epigenetic changes and its effects [3]<ul><li>Decreased acetylation of associated histones increases +ve charge of histones</li><li>Histones bind DNA (-ve charged) more tightly, preventing transcription factors binding; genes are not transcribed</li><li>Reversible.</li></ul> Recall how epigenetics is relevant to the development and treatment of cancer. [3]<ul><li>Epigenetic changes that increase the expression of an oncogene or that silence a tumor suppressor gene, can lead to tumour development</li><li>Tests can be used to see if a patient has abnormal levels of methyl or acetyl- early indicator of cancer</li><li>Could be manipulated to treat cancer (e.g drugs preventing histone acetylation / DNA methylation)</li></ul> What is miRNA?"- Formed as hair-pin bends of RNA but processed into <font color=""#ff0000"">single strands</font> 22-26 nucleotides long, both become incorporated into a protein-based RISC<div><br></div><div>(RNA-induced silencing complex)</div><div><br></div><div><img src=""meltzer-micro-rna-picture.jpg""><br></div>" What is siRNA?"- Formed as double-stranded molecules 21-25 bp long, <font color=""#ff0000"">one strand</font> incorperated into a protein-based RISC<div><br></div><div>(RNA-induced silencing complex)<br></div><div><br></div><div><br></div>" What are micelles?"<ul><li>tiny droplets consisting of fatty acids and monoglycerides surrounded by bile salts.</li></ul><div><img src=""3-s2.0-B9780128005132000048-f04-22-9780128005132.jpg""><br></div>" 5.1 - Contrast specific and non-specific immune responses<b>Non-Specific</b><div><ul><li>Immediate</li><li>Same for all pathogens</li></ul><div><b>Specific</b></div></div><div><ul><li>Longer lasting</li><li>Less rapid</li><li>Targeted response against a particular pathogen</li></ul></div> 5.5 - Explain the structure of an antibody (4)"<ul><li><b>4 polypeptide chains</b> <span style=""color: rgb(32, 33, 36);"">→</span> 2 heavy chains, 2 light chains</li><li><b>Variable region</b> <span style=""color: rgb(32, 33, 36);"">→ </span>contains specific binding site </li><li><b>Generic constant region</b> → allows attachment to phagocytic cells</li><li><b>Hinge </b><span style=""color: rgb(32, 33, 36);"">→ </span>allows for flexibility; hence can bind to multiple antigens</li></ul><div><img src=""paste-43c94dc586ff7c0588e379184fd6df00b302214a.jpg""><br></div>" 5.5 - How do antibodies lead to the destruction of an antigen? (2) <ul><li><b>agglutination</b>; cells clump together, making it easier for phagocytes to locate them </li><li>serve as <b>markers</b>; stimulate phagocytes to engulf cells</li></ul> 5.5 - Explain why antibodies are only effective against a specific pathogen (3)<ul><li>Antigens have a specific tertiary 3D structure</li><li>Shape of the antibody is complementary to the antigen</li><li>Antibody binds to the antigen, forming an antibody-antigen complex</li></ul> 5.5 - What is an antibody?<ul><li>Y shaped proteins made by plasma cells that form antigen-antibody complex during immune response</li></ul> 5.5 - State how antibodies deal with infection via neutralisation<ul><li>Antibodies bind to toxins / attachment proteins on a virus</li><li>Prevents the binding of these toxins / attachment proteins to the host cell</li></ul> 5.5 - State 3 applications of monoclonal antibodies<ol><li>Targeted medications</li><li>Medical Diagnosis</li><li>Pregnancy Testing                        </li></ol> 5.5 - State the two ways monoclonal antibodies are used to treat cancer<ul><li>Direct monoclonal antibody therapy</li><li>Indirect monoclonal antibody therapy </li></ul> 5.5 - Explain direct monoclonal antibody therapy for cancer<div><ol><li>Monoclonal antibodies produced → specific to cancer cell antigens</li><li>Antibodies given to patient + attach themselves to receptors on cancer cells</li><li>Blocks chemical signals that stimulate uncontrolled growth</li></ol></div> 5.5 - Explain indirect monoclonal antibody therapy<ul><li>Cytotoxic / radioactive drug attached to monoclonal antibodies</li><li>Cancer cells die when antibody attaches</li></ul> 5.5 - What are the advantages of antibody therapies with monoclonal antibodies?<ul><li>Specific</li><li>Reduces side effects</li><li>Smaller doses of drug required (indirect only)</li></ul> 5.5 - What does ELISA stand for?Enzyme linked immunosorbent assay  5.7 - What does an ELISA test allow us to do?<ul><li>detect and quantify the precense of specific antigens or antibodies e.g proteins, hormones, toxins, pathogens </li></ul> 5.7 - Describe the steps in the indirect ELISA test"1. Apply sample to surface (antigens attach)<br>2. Wash to remove unattached antigens<br>3. Add specific antibody + leave to bind<br>4. Wash to remove excess antibody<br>5. Add second antibody with enzyme attached to bind with first antibody.<br>6. Add colourless enzyme substrate to change colour.<br>7. Quantity = intensity<div><br></div><div><img src=""paste-430c4a1baf1d80af556a486beea8c59e564379b4.jpg""><img src=""paste-65fcb3f9aa390a58dbef52f7a427c06bfcbfe5e8.jpg""><br></div>" 5.7 - What's the difference between direct / indirect ELISA tests?"<ul><li>Indirect = two different antibodies</li><li>Direct = one specific antibody</li></ul><div><img src=""hqdefault.jpg""><br></div>" Recall the 2 reasons why we need a ELISA <b>control </b>well MS [2]<ul><li>shows that only the enzyme is causing a colour change </li><li>washing is effective / all unbound antibody is washed away</li></ul> 5.5 - How are monoclonal antibodies used in pregancy testing?<ul><li>a mother's urine has human chorionic gonadatrophin (hCG)</li><li>monoclonal antibodies on the pregnancy strip bind to these antibodies, which are linked to coloured paritcles</li><li>hcg-antibody-colour complex moves along the strip until it's trapped by a different type of antibody </li></ul> 5.5 - Describe 3 ethical considerations in the use of monoclonal antibodies• Animal testing → involves use of mice in antibody production + tumour cells.<br>• Informed consent → patients must know all risks + benefits of the drugs.<br>• Drug trials → testing on volunteers can be dangerous; issues over trial conduct. 5.7 - Describe the structure of HIV"<ul><li>Lipid envelope + attachment proteins embedded</li><li>Capsid encloses two single RNA strands + enzymes including reverse transcriptase</li><li>It's a <b>retrovirus </b>as it contains RNA </li></ul><div><img src=""paste-8b8b0234051c490457fda486c01230189ea7030b.jpg""><br></div>" 5.7 - Explain the process by which HIV replicates (7)"1. Enters bloodstream + circulates<br>2. Protein on HIV binds to CD4 protein (normally on T-Helper cells)<br>3. Protein capsid fuses + CSM. RNA + enzymes enter cell<br>4. Reverse transcriptase converts RNA → DNA<br>5. DNA inserted into host DNA<div>6. DNA transcribed into mRNA which uses ribosomes to make viral proteins</div><div>7. HIV leaves, using part of cell’s CSM to from lipid envelope.<div><br></div><div><img src=""Life-Cycle-800.jpg""><br></div></div>" 5.7 - What does AIDs stand for?acquired immunodeficiency syndrome 5.7 - How does HIV lead to the development of AIDs?<ul><li>attacks T<sub>H</sub> cells </li><li>infects immune system so sufferers cannot respond effectively to other pathogens</li><li>secondary diseases ultimately cause deaths </li></ul> 5.7 - Explain why antibiotics are ineffective against viral disease<ul><li>Antibiotics work by preventing bacteria making normal cell walls; causing them to burst when water enters via osmosis</li><li>Viruses rely on host cells for metabolic activities; no metabolic pathways for antibodies to disrupt</li><li>Viruses have a protein coat so do not have sites where antibiotics can work </li></ul> 5.6 - State 3 features of passive immunity and give 2 examples of natural/artificial passive immunity <ul><li>External source of antibodies</li><li>Immediate immunity</li><li>No lasting immunity</li><li><b>Natural </b>= Immunity of fetus</li><li><b>Artificial </b>= Antivenom </li></ul> 5.6 - State 3 features of active immunity and give 2 examples of natural/artificial active immunity <ul><li>Direct contact with the antigen, stimulates production of antigens by the individual's own system</li><li>Takes longer to develop (around 2 weeks)</li><li>Long lasting</li><li><b>Natural </b>= normal infection</li><li><b>Artificial </b>= vaccination</li></ul> 5.6 - State 5 features of a successful vaccination programme<ul><li> Economically available in sufficient quantities to immunise most of vulnerable</li><li>population → herd immunity</li><li> Few <b>side</b>-<b>effects</b></li><li> Means of <b>producing</b>, storing + transporting must be avaliable</li><li>Means of <b>administering</b>. e.g training staff </li></ul> 5.6 - What is herd immunity?When a sufficiently large proportion of the population has been vaccinated to make it difficult for a pathogen to spread within that population. 5.6 - How does herd immunity work?As a majority of the population has been vaccinated, it is highly improbable that a susceptible individual will come into contact with a infected person.  5.6 - Why is herd immunity so important?It's impossible to vaccinate everyone due to religious/ethical/medical objections  5.6 - Why may vaccination not completely eliminate a disease? (6) <ol><li>Fails to induce immunity in some people</li><li>Vaccinated individuals may harbour the pathogen and infect others</li><li>Antigenic Variability, where antigens change frequently</li><li>Varieties of pathogens / strains</li><li>Some pathogens ''hide'' from body's immune system </li><li>Medical/reiligious/ethical objections to taking the vaccine</li></ol> 5.6 - State some ethical issues with vaccinations<ul><li>animal testing</li><li>side effects</li><li>vaccination testing</li><li>trialling new vaccines with unknown health risks</li><li>investments into almost eradicated disease vsv other new ones</li><li>herd immunity -> should we make vaccines compulsory?</li><li>balancing individual risk and community risk </li></ul> "<div>Describe the difference between active and passive immunity. (5 marks)</div>""<div>1.      Active involves <b>memory cells</b>, passive does not;</div> <div>2.      Active involves <b>production </b>of <b>antibody </b>by plasma cells / memory cells;</div> <div>3.      Passive involves antibody introduced into body from <b>outside</b>;</div> <div>4.      Active <b>long term</b>, because antibody produced in response to antigen;</div> <div>5.      Passive short term, because antibody given is broken down;</div> <div>6.      Active can take time to <b>develop </b>/ work, passive fast acting.</div>" <div>What is vaccination? (2 marks)</div>"<div>Injection of antigens from attenuated microorganism;</div> <div>Stimulates the formation of memory cells;</div>" "<div>Vaccines protect people against disease. Explain how. (5 marks)</div>""<div>1.      Vaccines contain antigens from a dead/weakened pathogens are injected;</div> <div>2.      Memory cells made;</div> <div>3.      On second exposure memory cells produce become active and produce antibodies;</div> <div>4.      <u>Rapidly</u> produce antibodies/ produces <u>more</u> antibodies;</div> <div>5.      Antibodies destroy pathogens;</div>" "<div> Explain why the antibody will only detect this antigen. (3 marks)</div>""<div>1.      Antibody has a variable region with a specific amino acid sequence / primary structure;</div> <div>2.      The shape of tertiary structure of the binding site;</div> <div>3.      Complementary to the antigens;</div> <div>4.      Forms complex between antigen and antibody;</div>" 8.3 - What is a codon?sequence of three bases on mRNA that code for a single AA<div><br></div> 8.3 - Why is it significant that mRNA is chemically unstable?Polypeptide synthesis will not continue indefinitely 8.4 - What is transcription?The process of making pre-mRNA using part of the DNA as a template 8.4 - What is splicing? <ul><li>removal of introns</li><li>pre mRNA becomes mRNA </li><li>only in eukaryotic cells </li></ul> 8.4 - What is translation?<ul><li>mRNA used as a template to which complementary tRNA molecules carrying AAs attach </li><li>form a polypeptide when linked </li></ul> Describe the process of transcription MS [7]"<div>1.        DNA Helicase;</div> <div>2.      Breaks hydrogen bonds between base pairs, exposing them;</div> <div>3.      Only one DNA strand acts as a template;</div> <div>4.      RNA nucleotides attracted to exposed bases;</div> <div>5.      (Attraction) according to base pairing rule (A – U & C – G);</div> <div>6.      RNA polymerase joins the RNA nucleotides together, to form pre-mRNA;</div> <div>7.      Pre-mRNA is spliced to remove introns, forming mRNA</div>" Describe the process of translation MS [7]<ul><li>mRNA attaches to ribosome</li><li>Ribosome moves to start codon</li><li>tRNA anticodons bind to complementary mRNA codons</li><li>tRNA brings a specific amino acid</li><li>Amino acid join by peptide bonds with the use of ATP</li><li>tRNA released after AA joined to polypeptide</li><li>Ribosome moves along mRNA to form polypeptide </li></ul> Describe how a vaccination leads to the production of antibodies in the blood (6 marks)1.      Vaccine contains antigen from pathogen;<br>2.      Antigen is displayed on antigen-presenting cells (macrophages);<br>3.      Helper T cell with complementary receptor protein binds to antigen;<br>4.      Helper T cell stimulates specific B cell;<br>5.      With the complementary antibody on its surface;<br>6.      B cell secretes large amounts of antibody;<br>7.      B cell divides to form clones which produces the same antibody Outline the steps in crossing over (4)"<ul><li><b>Bivalents develop</b> → homologous chromosomes come together to form bivalents</li><li><b>Chiasmata form </b>→ non-sister chromatids wrap around each other, and join up at the chiasmata</li><li><b>Chromosomes break</b> → break up at the chiasmata, and sections of chromosomes are exchanged</li><li><b>Recombination occurs </b>→ final chromatids still have same genes, but have different combinations of alleles</li></ul><div><img src=""paste-1780c187f915d067e2bac060787404afd392e083.jpg""><br></div>" 9.2 - What is meant by 'independent segregration'?<div>Each chromosome is <b>inherited randomly </b>and independent of other chromosomes. </div> 9.2 - Comparison of Mitosis vs Meiosis<div><ul><li>Number of Daughter Cells</li><li>Genetic Diversity between Parents / Daughter Cells</li><li>Chromosome Number</li><li>Stages</li><li>Crossing over?</li><li>Separation of Homologous Pairs</li></ul></div>"<img src=""paste-8084a6380839af972fd1bb03548b419960137aad.jpg"">" How can we calculate the total possible number of <b>gametes </b>with different chromosome combinations?2<sup>n</sup> where n = number of pairs of homologous chromosomes  9.2 - What are the stages in Meiosis? Briefly describe what happens in each<ul><li><b>Interphase </b>- DNA replicates</li><li><b>Meiosis I </b>- produces 2 haploid (duplicated) daughter cells, crossing over occurs</li><li><b>Meiosis II</b> - two haploid (duplicated) daughter cells divide in order to produce a total of four haploid daughter cells, each with a single copy of every chromosome </li></ul> 9.2 - In what ways is meiosis I different to mitosis?<ul><li>Products aren't genetically identical</li><li>Crossing over occurs in Prophase I</li></ul> 9.2 - In what ways is Meiosis II different to mitosis?<ul><li>Products are 4 haploid daughter cells</li><li>Independent assortment of chromosomes</li></ul> 9.2 - What event occurs in Meiosis II that doesn't occur in Meiosis I?Centromeres split and sister chromatids are pulled apart  What are the key sources of diversity in meiosis?<ol><li>Crossing Over</li><li>Independent Segregation</li></ol> 9.2 - What is meiosis needed for?<ul><li>production of gametes and therefore sexual reproduction</li><li>genetic diversity</li></ul> At what stage of meiosis is the chromosome number halved?Meiosis I - products are two, haploid cells.  How can we calculate the total possible number of <b>zygotes </b>with different chromosome combinations?(2<sup>n</sup>)<sup>2</sup> where n = number of homologous chromosome pairs   What is non-disjunction?(3)<ul><li>Chromosomes do not separate properly during meiosis</li><li>Gametes have incorrect number of chromosomes</li><li>Can arise spontaneously </li></ul> How can non-disjunction occur? (3)<ul><li>failure of a pair of homologous chromosomes to separate in Meiosis I</li><li>failure of sister chromatids to separate during meiosis II</li><li>failure of sister chromatids to separate during mitosis</li></ul> 10.1 - What are the two main forms of biological classification?<ul><li>Artificial Classification</li><li>Natural (Phylogenetic) Classification</li></ul> 10.1 - What is artificial classification?<ul><li>division of organisms</li><li>based on <b>obvious differences </b>(colour, size etc.)</li><li>can be based on <b>analogous characteristics </b>(winged animals) </li></ul> 10.1 - What is natural / phylogenetic classification? (4)<ul><li>division of organisms</li><li>based on evolutionary relationships</li><li>based on shared characteristics that have been taken from ancestors</li><li>hierarchy of groups formed</li></ul> 10.1 - What are the 8 groups in Linnaeus' system of Classification?"<img src=""paste-a660728c11b11bda507bc8195d061c44363020a5.jpg""><br>" 10.1 - Describe the domain of Bacteria (5)<ul><li>70S ribosomes</li><li>Unicellular</li><li><b>Murein </b>Cell Walls</li><li>No membrane-bound organelles</li><li>Single loop of DNA, but no histones </li></ul> 10.1 - Describe the domain of Archaea (5)<ul><li>genes / proteins similar to eukaryotes</li><li>no murein in cell walls</li><li>more complex RNA polymerase</li><li>70S ribosomes</li><li>CSM - fatty acids attached to glycerol by ether linkages </li></ul> 10.1 - Describe the domain of Eukarya (5)<ul><li>mainly multicellular</li><li>cells contain membrane-bound organelles</li><li>membranes contain fatty acids linked to glycerol via ester bonds</li><li>80S ribosomes</li><li>cell walls chitin / cellulose</li></ul> "10.1 - Phylogenetic relationships can be shown using a <span class=""cloze"" data-cloze=""phylogenetic tree"" data-ordinal=""1"">[...]</span>""10.1 - Phylogenetic relationships can be shown using a <span class=""cloze"" data-ordinal=""1"">phylogenetic tree</span><br> " 10.1 - What are the two techniques that have clarified evolutionary relationships between organisms?<ul><li>immunological techniques</li><li>genome sequencing </li></ul> 10.1 - How have we used gene sequencing to identify phylogenetic relationships?"<ul><li>Determined the entire base sequence for a particular species</li><li>Compare to other species</li><li>Assess similarity </li><li><span style=""background-color: rgb(37, 255, 241);"">COMPARATIVE GENOMICS</span></li></ul>" 10.4 - How have we used immunological methods to clarify phylogenetic relationships?"<ul><li>proteins of different species can be compared using immunological techniques</li><li>antibodies of one species will respond to specific antigens on proteins in the blood serum of another</li><li>forms a precipitate - greater amount shows a closer evolutionary relationship </li></ul><div><img src=""paste-9c7dd6b0990641bb1a462232543648dbc224f2fc.jpg""><br></div>" Define the term species. [3]<ul><li>Group of similar organisms</li><li>Produce offspring</li><li>That are fertile</li></ul> What 3 components can biodiversity be separated into?<ul><li>Species</li><li>Genetic</li><li>Ecosystem</li></ul> 10.2 - What are the 3 different aspects of biodiversity?<ul><li>ecosystem diversity </li><li>genetic diversity </li><li>species diversity </li></ul> 10.2 - What is ecosystem diversity?Range of different habitats within an area  GCSE Definitions:<div><ul><li>Community</li><li>Population</li><li>Ecosystem</li></ul></div><b>Community </b>- all living organisms within a given area<div><br></div><div><b>Population </b>- made up of members of single species, within a given area</div><div><br></div><div><b>Ecosystem </b>- all living organisms and the non living components</div> Meiosis results in cells that have the haploid number of chromosomes and show genetic variation. Explain how. [7]<ul><li>HC pair up to form bivalence</li><li>Crossing over occurs through the formation of a chiasma</li><li>This produces new combination of alleles</li><li>Chromosomes then separate</li><li>Randomly</li><li>Produces varying combinations of chromosomes</li><li>Chromatids separated meiosis II</li></ul> Compare and contrast the structure of mRNA and tRNA. [6]<ul><li>mRNA does not have H bonds, tRNA does</li><li>mRNA is linear chain, tRNA is cloverleaf</li><li>mRNA does not have an amino acid binding site, tRNA does</li><li>mRNA has more nucleotides</li><li>Different mRNAs have different lengths, all tRNAs are similar lengths</li><li>mRNA has codons, tRNA has anticodons</li></ul> "10.3 - Farming techniques reduce <span class=""cloze"" data-cloze=""biodiversity&nbsp;"" data-ordinal=""1"">[...]</span>""10.3 - Farming techniques reduce <span class=""cloze"" data-ordinal=""1"">biodiversity </span><br> " 10.3 - Explain how monoculture is used in agriculture. <ul><li>involves the rowing of a single crop in an area </li><li>more water, mineral ions, carbon dioxide</li><li>pesticides can be used to reduce number of pests that damage crop plants</li></ul> 10.3 - Explain the disadvantages of monoculture<ul><li>pesticides could kill beneficial animals</li><li>costly - need to maintain the environment and monitor number of other organisms</li><li>if any pests do survive, then a monoculture enables them to spread rapidly</li></ul> 10.4 - What is traditional taxonomy and it's limitations?<ul><li>comparison of <b>the frequency of observable characteristics</b></li><li>limited by <b>polygenic </b>(coded for by more than one gene)<b> </b>features + environmental affects</li></ul> 10.4 - In modern taxonomy, we can compare organisms through similarities/differences of their...<ul><li>DNA base sequences</li><li>mRNA base sequences (compementary to the strand of DNA)</li><li>Sequence of amino acid (determined by mRNA)</li></ul> 10.5 - What is the difference between <b>inter</b>specific and <b>intra</b>specific variation?interspecific variation = one species differing from another<div><br></div><div>intraspecific variation = members of the same species differing</div> 10.5 - In what ways may a sample collected be unrepresentative?  <i>(2)</i><div><br></div><ul><li>sampling bias - unrepresentative due to the selection process</li><li>chance - unrepresentative due to chance</li></ul> 10.5 - Quantitative investigations of variation within a species involve:<ul><li>collecting data from random samples</li><li>calculating a mean value of the collected data</li><li>calculating standard deviation of that mean</li><li>interpreting mean values + their standard deviations</li></ul> 10.5 - How do we minimise the effect of chance from the sampling process?<ul><li>using a large sample size - lessens the influence of anomalies</li><li>analysis of the data collected - statistical tests to determine how much of the results was influenced by chance</li></ul> 9.1 - What are the 3 types of mutation?<ul><li>base substitution</li><li>base deletion</li><li>base insertion</li></ul> What is base substitution?"A nucleotide in a DNA molecule is replaced by another nucleotide that as a <b>different base</b><div><b><br></b></div><div><img src=""aHR0cHM6Ly9pLmltZ3VyLmNvbS9vaXVaRVNHLnBuZw==.png""><b><br></b></div>" What is base insertion / deletion?<ul><li>nucleotide lost / gained from the normal DNA sequence</li><li>causes a frame shift, so the entire AA sequence is changed usually </li></ul> "Mutagenic agents can <span class=""cloze"" data-cloze=""increase the rate of mutation"" data-ordinal=""1"">[...]</span>""Mutagenic agents can <span class=""cloze"" data-ordinal=""1"">increase the rate of mutation</span><br> " "Gene mutations involve a <span class=""cloze"" data-cloze=""change in the base sequence of chromosomes"" data-ordinal=""1"">[...]</span> ""Gene mutations involve a <span class=""cloze"" data-ordinal=""1"">change in the base sequence of chromosomes</span> <br> " "9.1 - Mutations can arise <span class=""cloze"" data-cloze=""spontaneuously"" data-ordinal=""1"">[...]</span> during <span class=""cloze"" data-cloze=""DNA replication"" data-ordinal=""1"">[...]</span> ""9.1 - Mutations can arise <span class=""cloze"" data-ordinal=""1"">spontaneuously</span> during <span class=""cloze"" data-ordinal=""1"">DNA replication</span> <br> " Why might a mutation not result in a change in the sequence of amino acids?<ul><li>genetic code is <b>degenerate</b></li><li>meaning that an amino acid is coded for by more than one triplet </li><li>hence, even after a change, the same amino acid may still be coded for</li></ul> 9.1 - What are chromosome mutations? Two forms?<ul><li>change in the structure or number of chromosomes</li><li>changes in whole sets of chromosomes, organisms having 3+ sets rather than 2. This is called <b>polyploidy</b>. </li><li>changes in number of individual chromosomes ( <b>non-disjunction</b> during meiosis)</li></ul> "<div>Describe the behaviour of chromosomes during mitosis and explain how this results in the production of two genetically identical cells. (7 marks)</div>""<div>1       chromosomes shorten & thicken;</div> <div>2       chromosomes made from two <u>identical</u> chromatids, due to replication in interphase;</div> <div>3       chromosomes move to equator of the cell;</div> <div>4       Chromosomes attach to individual spindle fibres;</div> <div>5       Spindle fibres contract & the centromeres divide;</div> <div>6       Sister chromatids move to opposite poles;</div> <div>7       Each pole receives all the genetic information;</div> <div>8       Nuclear envelope re-forms around each group of chromosomes</div>" "<div>Describe what happens to chromosomes in meiosis (6 marks)</div>""<div>1.  Chromosomes <b style="""">shorten </b>& <b style="""">thicken</b>;<br> 2.  Chromosomes associate into their homologous pairs;<br> 3.  Crossing-over occurs between chromosomes, through the formation of a chiasma;<br> 4.  Chromosomes join to <u style="""">spindle</u> fibres, via their centromeres<br> 5.  Whilst at the equator<br> 6.  Homologous chromosomes move to opposite poles<br> 8.  Pairs of chromatids separated in 2<sup style="""">nd</sup> division;</div>" "<div>Meiosis results in <b style="""">genetic variation </b>in the gametes which leads to variation in the offspring formed by sexual reproduction. Describe how meiosis causes this variation and explain the advantage of variation to the species. (5 marks)</div>""<div>1.  Crossing-over; </div> <div>2.  Independent assortment (segregation of homologous chromosomes) in meiosis I;<br> 3.  Independent assortment (segregation of chromatids) in meiosis II;</div> <div>+   <u style="""">Any <b>three</b> from:<br> </u>4.  Causes individuals to have different adaptations making some better adapted;<br> 5.  Better adapted survive;<br> 6.  To reproduce;<br> 7.  These pass on the gene / allele;<br> 8.  Allows for changing environment / different environment</div>" "<div>Describe and explain how selection will have affected the genetic diversity of a species (2 marks)</div>""<div>1.      Diversity reduced as fewer different alleles present creating a smaller gene pool;</div> <div>2.      As <u style="""">alleles</u> have been chosen or rejected;</div>" Compare and contrast the DNA in eukaryotic cells with the DNA in prokaryotic cells. [7]Comparisons:<div><ul><li>Identical nucleotide structure</li><li>Nucleotides joined by phosphodiester bonds</li><li>DNA in mitochondria/chloroplasts similar to DNA in prokaryotes</li></ul>Contrasts:</div><div><ul><li>Eukaryotic DNA is longer</li><li>Eukaryotic DNA contain introns, prokaryotic DNA does not</li><li>Eukaryotic DNA is linear, prokarytoic DNA is circular</li><li>Eukaryotic DNA is associated with histones, prokaryotic DNA is not<br></li></ul></div> Explain the principles which biologists use to classify organisms into groups. [3]<ul><li>Large groups divided into smaller groups</li><li>Members of a group have features in common based on DNA</li><li>Reflects evolutionary history</li></ul> What type of molecule are carbohydrates?<div><ul><li>Polymers</li><li>Polymers are made up of monomers, which are small units of the structure that join to form the polymer</li><li>Carbohydrates are made form monosaccharide monomers</li></ul></div> What three elements do carbohydrates contain?C, H and O Give three examples of monosaccharide monomers that make up carbohydrates:<ul><li>Glucose<br></li><li>Fructose</li><li>Galactose</li></ul><div></div> What type of sugar is glucose?hexose / monosaccharide Draw a diagram of alpha glucose:"<img src=""paste-d03a0179da22733e8bdd37fff3d0ac1dd0f64147.jpg"">" Draw a diagram of beta glucose:"<img src=""paste-3019f6d218c233fc19837ca9e7c60ceed65fc736.jpg"">" Draw a diagram showing the difference between alpha and beta glucose:"<img src=""paste-bc1475586c07ccbec62f77e80209754619c86338.jpg"">" What is a condensation reaction?When two molecules join by forming a chemical bond, and a small molecule (such as water) is released How do monosaccharides join together to form carbohydrates?Condensation polymerisation What type of bond forms between monosaccharides to form carbohydrates?A glycosidic bond What is a disaccharide?Formed when two monosaccharides join together and form a glycosidic bond between them What is formed when two alpha glucose molecules join together?Maltose What is sucrose?<div><ul><li>A <b>disaccharide</b></li><li>Formed by a condensation reaction between a glucose molecule and a fructose molecule</li></ul></div> What is lactose?<div><ul><li>A disaccaride</li><li>Formed by a condensation polymerisation reaction between a glucose molecule and a galactose molecule</li></ul></div> How can carbohydrates (polymers) be broken down?<div><ul><li>By <b>hydrolysis </b>reactions<br></li><li>This involves water breaking the bond between monomers<br></li><li>The opposite of a condensation reaction<br></li><li>Carbohydrates are broken down into monosaccharide</li></ul></div> What are the two types of sugars in biology?<div>Reducing sugars</div><div>Non-reducing sugars</div> What test is used to test for sugars?Benedict’s Test Describe the process of using Benedict’s test to test for reducing sugars:"<div>All monosaccharides (glucose), some disaccharides (maltose and lactose)</div><div><br></div><div><ul><li>Add blue Benedict’s reagent to the sample</li><li>Heat the solution using a water bath</li><li>A coloured precipitate will form if the test is positive</li><li>The higher the concentration of sugar, the further the colour change will be along the scale below:</li></ul><div><img src=""paste-209fdb9a6299b954e34866137451c13bc945b9db.jpg""><br></div></div><div><ul><li>Alternatively, the solution can be filtered and the precipitate weighed (this is more accurate)</li></ul></div>" Describe the process of using Benedict’s test to test for non-reducing sugars:<br>"<div>This test is carried out if the reducing sugar test is negative</div><div>E.g. sucrose</div><div><ul><li>Add dilute hydrochloric acid</li><li>Heat the solution in a water bath</li><li>Neutralise the solution with sodium hydrogencarbonate</li><li>Repeat the Benedict’s test as for non-reducing sugars</li><li>The solution staying blue means not even a non-reducing sugar is present</li><li>A colour change along the scale means a non-reducing sugar is present:</li></ul><div><img src=""paste-9c67c5aecd161506137d4930e7d4c5d378e54fee.jpg""><br></div></div>" What is a polysaccharide?A sugar / polymer formed when more than two monosaccharides join together by condensation reactions Give three types of polysaccharide:<ul><li>Starch<br></li><li>Glycogen</li><li>Cellulose</li></ul> What is starch?<ul><li>A polysaccharide used by plants to store excess glucose for energy<br></li><li>On demand the starch can be broken down to release glucose</li></ul> What is amylose?<div><ul><li>A long unbranched chain of alpha glucose<br></li><li>A coiled structure<br></li><li>Compact<br></li><li>Good for storage</li></ul></div> What is amylopectin?<ul><li>A long branched chain of alpha glucose<br></li><li>Side branches mean enzymes can break down the molecule via the glycosidic bonds easily</li><li>Glucose can be released quickly</li></ul> How do you test for starch?<div><ul><li>Use the iodine test<br></li><li>Add iodine dissolved in potassium iodide solution<br></li><li>Starch present will cause the brown/orange to change to a black/blue colour</li></ul></div> What is glycogen?<div><ul><li>A polysaccharide of alpha-glucose<br></li><li>Similar to amylopectin, but with more side branches<br></li><li>Glucose can be released quickly<br></li><li>Compact, so good for storage</li></ul></div> What are triglycerides? Draw the structure:"<div>One molecule of glycerol, three fatty acids attached</div><div><br></div><div><img src=""paste-64fb9dda88e36af0afc9c5a96fef12e0be585611.jpg""><br></div><div><ul><li>Hydrocarbon tail made of fatty acids</li><li>The tail is hydrophobic</li><li>The lipids are therefore insoluble in water</li></ul></div>" What is the structure of a fatty acid?"<img src=""paste-8ea3f1833a26a53f9785d0c44b05c5de47e93398.jpg"">" What are the two types of fatty acid?<div>Saturated fatty acids</div><div>Unsaturated fatty acids</div> How are triglycerides formed?<div><ul><li>Formed by condensation reactions</li><li>The H of a glycerol molecule joins to the OH of a fatty acid to make water, hence the condensation reaction<br></li><li>This happens for all 3 fatty acids that attached</li></ul></div> What are saturated fatty acids?No double bond between carbon atoms of the hydrocarbon tail What are unsaturated fatty acids?<br>At least one double bond between carbon atoms that causes the hydrocarbon tail chain to kink What are phospholipids? Draw a diagram of the structure:"<div><ul><li>Found in cell membranes<br></li><li>One fatty acid molecule is replaced by a phosphate group<br></li><li>The phosphate group is hydrophilic and attracts water</li><li>The fatty acid tail is hydrophobic and repels water</li><li>This helps the cell membrane function</li></ul><div><img src=""paste-d8c50a79d02604eabca2f07cb511f89e5108c28b.jpg""><br></div></div>" In what ways does the structure of a triglyceride make it useful as an energy storage molecule?"<ul><li>Long hydrocarbon tails contain lots of energy<br></li><li>Lots of energy is released when they are broken down</li><li>Insulated and don’t affect the water potential, meaning water doesn’t enter cells by osmosis because of the presence of triglycerides</li><li>They form insoluble droplets, with the hydrophobic water-repelling tail inwards</li></ul><div><img src=""paste-bd6de493845ef5251f9893d1081fdf2b0f1d1acd.jpg""><br></div>" How does the structure of a phospholipid make it useful for being in a cell membrane?"<ul><li>Make the bilayer in cell membranes<br></li><li>Control what enters and leaves the cell</li><li>Hydrophilic head</li><li>Hydrophobic tail</li><li>Water soluble substances are not able to easily pass through the hydrophobic centre</li></ul><div><img src=""paste-dc90f767f11caac654bb7794a57d7b2f5d6654de.jpg""><br></div><div><br></div>" What monomers make up proteins?<div>Amino acids</div> What is a dipeptide?<div>Two amino acids joined together</div> What is a polypeptide?Formed when more than two amino acids join together Draw the structure of a general amino acid:"<img src=""paste-77505e0e39a81dd94e77c2cce9890e3a1ce2c5f6.jpg"">" How are polypeptides formed?<div>Condensation reactions involving amino acids, where water is released</div><div><br></div><div>Peptide bonds are between the amino acids</div> What are the structural levels of proteins?<ul><li>Primary structure<br></li><li>Secondary structure</li><li>Tertiary structure</li><li>Quaternary structure</li></ul> Describe the primary structure of proteins:The sequence of amino acids n the polypeptide chain Describe the secondary structure of proteins:<br><ul><li>Hydrogen bonds form between the amino acids of the polypeptide chain<br></li><li>The chain coils into an alpha helix or folds into a beta pleated sheet</li><li>The coil/fold makes the secondary structure</li></ul> Describe the quaternary structure of proteins:<br><ul><li>The assembly of two or more polypeptide chains<br></li><li>Held by bonds</li><li>Proteins with more than one polypeptide chain have the quaternary structure as their final 3D structure</li></ul> List 4 types of protein molecules found in organisms:<ul><li><b>E</b>nzymes<br></li><li><b>A</b>ntibodies</li><li><b>T</b>ransport proteins</li><li><b>S</b>tructural proteins</li></ul> Describe the structure of proteins as enzymes:<ul><li><b>Spherical shape </b>since the polypeptide chains are tightly folded<br></li><li>Soluble to be used in metabolic processes</li><li>Used as digestive enzymes, and in biological molecule synthesis</li></ul> Describe the structure of channel proteins<br><ul><li>In <b>cell membranes</b><br></li><li>e.g channel proteins:</li><ul><li>Contain both hydrophilic and hydrophobic amino acids</li><li>The protein folds up and forms a channel</li><li>These proteins can transport substances (molecules and ions) across membranes</li></ul></ul> Describe the structure of structural proteins:<br><ul><li>Long polypeptide chains<br></li><li>Strong proteins</li><li>The polypeptide chains lay close or cross-linked</li><li>e.g. keratin in nails and hair, and collagen in connective tissue</li></ul> Recall the test for proteins. MS [2]<ul><li>Add Biruet's reagent </li><li>Positive result is purple/violet</li></ul> What does it mean to call enzymes ‘biological catalysts’?They catalyst metabolic reactions at cellular level (respiration) and in the organism as a whole (digestion) How do enzymes lower activation energy? [2]"<div><ul><li>Enzymes <b>attach </b>to <b>substrates </b>and can hold the two substrates close together,<b><font color=""#ff0000""> reducing repulsion</font></b> and allowing bonding to occur more easily</li><li>Enzymes <b>breaks up the substrate </b>more easily as it applies<b><font color=""#ff0000""> strain on the bonds</font></b></li></ul></div>" What is the lock and key model for enzyme-substrate action?"<div><ul><li>The substrate fits into the enzyme like a<font color=""#ff0000""><b> key fits a lock</b></font></li><li>This was before the induced fit model that came based upon new evidence</li></ul></div>" Describe the induced fit model for enzyme action. MS [3]"<ul><li>Active site of enzymes is <b>not <font color=""#ff0000"">complementary to substrate</font></b></li><li>Shape of active site undergoes a <b><font color=""#ff0000"">conformational change</font> when substrate binds to form an E-S complex</b></li><li>Stressing/distorting/bending bonds in substrates leads to reaciton</li></ul>" What 4 factors can affect enzyme activity?<ol><li>Temperature<br></li><li>pH</li><li>Enzyme concentration</li><li>Substrate concentration</li></ol> How does increasing temperature closer to the optimum affect enzyme activity? MS [4]"<ul><li>Rate <font color=""#ff0000""><b>increases </b></font>when temperature increases<br></li><li><font color=""#ff0000""><b>More kinetic energy</b></font> hence moving faster<br></li><li>More <b><font color=""#ff0000"">frequent collisions</font></b> between enzyme and substrate molecules</li><li>More E-S complexes formed</li></ul>" Describe how increasing temperature <b>too much </b>affects enzymes in chemical reactions:<ul><li>Bonds (e.g H bonds, Ionic bonds, Disulfide Bridges) in tertiary structure broken</li><li>Active site changes shape </li><li>Enzyme is denatured</li><li>Enzyme active site no longer specific to substrate molecule hence no E-s complexes</li></ul><div></div> How does pH affect enzyme activity?<br>"<div><ul><li>Enzymes have an <font color=""#ff0000""><b>optimum pH</b></font> to work in</li><li>Above and below the optimum pH, the presence of more/less than ideal numbers of H+ and OH- ions can damage i<font color=""#ff0000""><b>onic bonds</b></font> in the enzymes tertiary structure</li><li>This causes the enzyme to be <font color=""#ff0000""><b>denatured</b></font></li></ul></div>" How does enzyme concentration affect enzyme activity?<div><ul><li>More <b>enzyme molecules </b>in a solution means they are more likely to collide with a substrate and form an enzyme-substrate complex</li><li>Increasing enzyme concentration increases reaction rate</li><li>If the amount of substrate is limited, adding more enzyme won’t increase the rate any further</li></ul></div> How does substrate concentration affect the rate of reaction?<div><ul><li>The higher the substrate concentration, the faster the reaction<br></li><li>Collisions between substrate and enzyme are more likely, and so more active sites are used<br></li><li>This is limited by the saturation point where all the active sites are full and adding more substrate does not help</li></ul></div> What happens to substrate concentration as a reaction progresses?"<div><ul><li>[ ] <b><font color=""#ff0000"">decreases </font></b>with time during the reaction</li><li>Hence rate of reaction will <b><font color=""#ff0000"">decrease </font></b>over the course of a reaction</li><li><b><font color=""#ff0000"">initial rate highest</font></b> as the most substrates are available</li></ul></div>" How can you measure the rate of an enzyme controlled reaction?<div>Two ways:</div><div><ol><li>How fast the product of the reaction appears</li><li>Disappearance of the substrate</li></ol><div></div></div> Describe investigating the action of enzymes by the rate of disappearance of the substrate:<br><div><br></div><div>(starch experiment)</div><div><ul><li>Used with measuring the breakdown of starch to maltose using amylase</li><li>You can detect starch with potassium iodide and iodine</li><li>Time how long it takes for the starch to disappear</li><li>Conditions can be altered and rates compared</li></ul></div> Describe how you would investigate the effect of temperature on catalase activity:<ul><li>Prepare boiling tubes with the same volumes and concentration of hydrogen peroxide<br></li><li>Keep the pH identical by adding equal buffer solutions</li><li>Set up a bath of water and an upside down measuring cylinder with a delivery tube</li><li>Put each tube in a water path at different temperatures - for example 10ºC, 20ºC up to 40ºC</li><li>Pipette the same volume and concentration of catalase into each test tube</li><li>Record the volume of oxygen made in the first 60 seconds - using a stopwatch to measure the time</li><li>Repeat 3 times, find the average volume of oxygen produced for each of the temperatures used</li><li>Calculate mean reaction rate, in cm3/second</li></ul> How can you calculate the initial rate of reaction?<ul><li>Draw a tangent to the graph at t = 0<br></li><li>Calculate the gradient of the line</li><li>This is the rate of reaction</li></ul> Describe how you would test a piece of food for the presence of lipid: MS [2]<ul><li>Dissolve in alcohol then add water<br></li><li>White emulsion would show the presence of lipid</li></ul> "E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why: MS [2]"<ul><li>The cell cannot change shape</li><li>It has a cell wall</li><li>The wall is rigid</li></ul> Give similarities between starch and cellulose. [6]<div><div><b><u>Similarities</u></b>:</div><ul><li>Both polysaccharides</li><li>Contain glucose</li><li>Contain glycosidic bonds</li><li>Have 1-4 links</li><li>Hydrogen bonding within the structure</li></ul></div><div><br></div> Contrast starch and cellulose. MS [6]<div><ul><li>Alpha vs beta glucose</li><li>Helical + branched vs linear structure<br></li><li>1,6 bonds vs only 1,4</li><li>No hydrogen bonding between molecules in starch</li><li>No fibres in starch</li></ul></div><div><div></div></div> Omega-3 fatty acids are unsaturated. What is an unsaturated fatty acid? MS [2]<div>Double bonds</div><div>Are present between the carbons</div> "Maltose is hydrolysed by the enzyme maltase. Explain why maltase catalyses only this reaction: MS [3]"<ul><li>The active site has a shape complimentary to the substrate<br></li><li>Only maltose is able to bind</li><li>To form the enzyme substrate complex</li></ul> What is DNA?<div><ul><li>Deoxyribonucleic acid</li><li>Stores genetic information for the organism</li></ul></div> What is RNA?<div><ul><li>Ribonucleic acid<br></li><li>Similar structure to DNA<br></li><li>Transfers genetic information from DNA to ribosomes</li><li>Ribosomes read the RNA, and make polypeptides during the ‘translation’ process</li></ul></div> What is a nucleotide made from?<ul><li>A pentose sugar<br></li><li>A base (nitrogen-containing organic base)</li><li>A phosphate group</li></ul> Draw a diagram of a nucleotide:"<img src=""paste-a07fe2d3571dbbd540cf3824b75c00120302b5b3.jpg"">" What are nucleotides?Monomers that make up RNA and DNA What is a polynucleotide?"<ul><li>A polymer of nucleotides<br></li><li>They join by condensation polymerisation</li><li>A phosphodiester bond is formed</li></ul><div><br></div><div><img src=""paste-2756fece608b396e36f1e154f20f147ed90eb398.jpg""><br></div>" Describe the structure of DNA:<ul><li>Two DNA polynucleotide strands join by hydrogen bonding between bases<br></li><li>Only complimentary base pairing occurs:</li><ul><li>A and T bind (two hydrogen bonds)</li><li>C and G bind (three hydrogen bonds)</li></ul><li>The structure is a double helix</li></ul> What type of replication does DNA use?<div><ul><li>Semi-conservative replication</li><li>Half the strands in each new DNA molecule are from the original DNA molecule</li></ul></div><div><br></div> Recall the process of DNA replication. <ul><li><b>DNA helicase</b>, an enzyme, breaks hydrogen bonds between the bases of the two polynucleotide DNA strands<br></li><li>The helix unwinds</li><li>Each original strand is used as a template</li><li>Free floating DNA nucleotides are attracted to exposed bases (to engage in complimentary base pairing)</li><li>The strands join by condensation reactions, the reaction is catalysed by DNA polymerase</li><li>Hydrogen bonds form</li><li>New DNA contains one original strand, and one new strand</li></ul> What are the two ends of a DNA strand?<div>One end is called 3’ (three prime)</div><div>The other end is called 5’ (five prime)</div><div><br></div><div>The strands run in opposite directions, antiparallel</div> How do DNA strands run?In opposite directions - ‘antiparallel'<br> How does DNA polymerase arrange itself around a new DNA strand?<div>DNA polymerase’s active site is only complimentary to the 3’ end of a DNA strand</div><div><br></div><div>New strands are therefore made from 5’ to 3'</div> Who came up with the semi-conservative DNA replication mechanism?<div>Watson and Crick</div><div><br></div><div>Meselson and Stahl’s experiment later verified the theory</div> Describe how Meselson and Stahl showed that DNA replication was a semi-conservative process:<div>Uses heavy nitrogen (15N) and light nitrogen (14N)</div><div><ul><li>Bacteria were grown in a broth containing light nitrogen</li><li>Bacteria were grown in a broth containing heavy nitrogen</li><li>The nitrogen became part of the DNA as the bacteria made nucleotides</li><li>A sample of DNA was taken and spun in a centrifuge</li><li>Heavy nitrogen bacteria DNA settle lower down the tube, the light nitrogen DNA extracted settled higher in the tube</li><li>DNA from the heavy broth was put into an only light nitrogen broth</li><li>The process was repeated, but the sample was spun in a centrifuge again and the DNA extracted settled lower than original light nitrogen (n14 / n15 DNA now present)</li><li>This implied semi-conservative replication</li></ul></div> What type of molecule is water?<div><ul><li>A polar molecule<br></li><li>The oxygen has a delta negative charge<br></li><li>The hydrogens have a delta positive charge each<br></li><li>These slight charges can lead to attraction, called hydrogen bonding</li></ul></div> How is water an important metabolite?<ul><li>Used in lots of important <b>condensation</b>/<b>hydrolysis </b>reactions<br></li><li>In hydrolysis, water is needed to break bonds</li><li>In condensation, water is released when a new bond is formed</li><li>e.g energy released from ATP form a hydrolysis reaction</li><li>e.g. condensation reactions forming polypeptide</li></ul> Why is it useful that water has a high heat of latent vaporisation?<ul><li>Lots of energy is require to break hydrogen bonds between water molecules<br></li><li>Lots of energy is used up during evaporation</li><li>This is useful for organisms trying to cool down (such as sweating)</li></ul> How is water a buffer?<ul><li>It can resist changes in temperature<br></li><li>Hydrogen bonds are able to absorb lots of energy</li><li>This gives water a high specific heat capacity</li><li>Water cannot undergo large temperature changes in short amounts of time</li><li>This means water is a good habitat, and also a a good substance to maintain constant body temperature</li></ul> Why is water a good solvent?<ul><li>Lots of substances in metabolic reactions are ionic (salts for example)<br></li><li>Water has a slightly positive charge on the hydrogen atoms, and a slightly negative charge on the oxygen</li><li>The polarity means water molecules can attract charged substances</li><li>This is how dissolving works</li><li>Water is therefore a good solvent</li></ul> Why is there strong interaction (cohesion) between water molecules?<ul><li>The polarity of water molecules means water molecules stick together<br></li><li>The cohesion helps water flow</li><li>This is useful for xylem in plants, to transport substances along a chain</li><li>Strong cohesion leads to high surface tension</li><li>This is useful for supporting smaller organisms</li></ul> What is respiration?<div>The process that plants and animals used to release energy from glucose</div> Why is ATP needed?<div><ul><li>Energy can’t be directly released from glucose</li><li>Energy released from glucose makes ATP</li></ul></div> What is ATP?"<div><ul><li>The nucleotide tide base is adenine</li><li>The pentose sugar is called ribose</li><li>There are three phosphate groups</li><li>A modified nucleotide, known as a nucleotide derivative</li><li>Energy is stored in bonds between phosphate groups, and released by hydrolysis reactions</li></ul><div><img src=""paste-577bfb8c694409311a17b5ac9287e61ebc843b49.jpg""><br></div></div>" How is energy released from ATP?<ul><li>ATP is broken down under a hydrolysis reaction</li><li>Broken down into ADP (adenine diphosphate) and Pi (inorganic phosphate)</li><li>The phosphate bonds are broken, and energy is released</li><li>This is catalysed by ATP hydrolase, an enzyme</li></ul> How is the inorganic phosphate (Pi) released from the hydrolysis of ATP used?<div><ul><li>Added to another compound by phosphorylation<br></li><li>This makes the compound more reactive</li></ul></div> How can ATP be resynthesised?<ul><li>A condensation reaction<br></li><li>Between ADP and Pi</li><li>This occurs during respiration and photosynthesis</li><li>Catalysed by ATP synthase</li></ul> What is an inorganic ion?An ion that doesn’t contain carbon Where are inorganic ions found?<ul><li>In cell cytoplasms<br></li><li>In bodily fluids of organisms</li><li>The role of the ion determine the required concentrations of the ions</li></ul> Where are iron ions required in the body?<ul><li>In haemoglobin, used in red blood cells<br></li><li>Made of four polypeptide chains that each have an Fe2+ ion in the centre</li><li>The Fe2+ binds to the oxygen in haemoglobin</li><li>The Fe2+ ion becomes a Fe3+ ion until the oxygen leaves</li></ul> Where are hydrogen ions required in the body?<br><ul><li>Across the whole body, the concentration of hydrogen ions determines the pH<br></li><li>More hydrogen ions means more acidic conditions</li><li>Enzyme activity is affected by the pH of the environment</li></ul> Where are sodium ions required in the body?<br>Used in co-transport across cell membranes of substances such as glucose and amino acids Describe the role of DNA polymerase in DNA replication: MS [1]Joins nucleotides to form new strands ATP is useful in many biological processes. Explain why MS [4]<ul><li>Releases energy in small / manageable amounts</li><li>Broken down in a one step reaction </li><li>Phosphorylates other compounds to make them more reactive</li><li>Reformed / remade / easily resyntesised</li></ul> Write a simple equation to show how ATP is synthesised from ADP: MS [1]ADP + Pi → ATP "Humans synthesise more than their body mass of ATP each day. Explain why it is necessary for them to synthesise such a large amount of ATP: MS [2]"<div>ATP cannot be stored it is an immediate source of energy</div><div>Only a small amount of energy is released at a time</div> What are prokaryotic cells?<div>Single celled organisms</div><div>Small and simple</div><div>E.g. bacteria</div> What is the main difference between fungal cells and plant cells?<div>Fungal cells are like plant cells, except:</div><div><ul><li>Cell walls are made of chitin, instead of cellulose</li><li>They don’t have chloroplasts</li></ul><div></div></div> Which extra organelles do plant cells have compared to animal cells?<ul><li>A cellulose cell wall, that has plasmodesmata channels used for substance exchange with adjacent cells<br></li><li>A vacuole full of cell sap</li><li>Chloroplasts</li></ul> What is a mitochondrion, and what is its function?<br>"<ul><li>Oval shaped<br></li><li>Double membrane</li><li>Inner membranes are folded to form cristae</li><li>Has a matrix inside - this contains enzymes involved in respiration</li></ul><div><img src=""paste-85ee5f0307e8929949375963dac61448d5c786a5.jpg""><br></div><div><ul><li>Site of aerobic respiration</li><li>ATP produced here</li><li>Found in large numbers in active cells that have high energy requirements</li></ul></div>" What is a golgi apparatus, and what is its function?<br><ul><li>A group of fluid-filled membrane bound flattened sacs</li><li>Processes and packages new lipids and proteins</li><li>Makes lysosomes</li></ul><div></div> What is a Golgi vesicle and what is its role?<ul><li>A small fluid filled sac<br></li><li>Surrounded by a membrane</li><li>Made by the Golgi apparatus</li><li>Stores lipids and proteins that are made by the Golgi apparatus</li><li>Transports them out of the cell by the cell surface membrane during exocytosis</li></ul> What is a ribosome, and what is its structure/function?<br>"<ul><li>Site for<b><font color=""#ff0000""> protein synthesis</font></b></li><li>Floats free in the cytoplasm or attached to the rough endoplasmic reticulum<br></li><li>Made of <font color=""#ff0000"">proteins </font>and <b><font color=""#ff0000"">rRNA</font></b></li></ul><div><img src=""paste-07d7de662d03b5059b73a8c2cbc09f189edfc3cf.jpg""><br></div><div><br></div>" What is a smooth endoplasmic reticulum (SER), and what is its function?<br><div><br></div><ul><li>Network of fluid-filled membranes</li><li>Produces and processes lipids</li></ul> What is a cell wall, and what is its function?<br><ul><li>Rigid cellulose structure that surrounds plants</li><li>Provides structural support to the plant and therefore keeps it rigid</li></ul><div></div> What is a vacuole, and what is its function?<br><ul><li>An organelle found enclosed by a membrane<br></li><li>In the cytoplasm of plant cells</li><li>Contains sap - a weak solution of salts and sugar</li><li>The membrane surrounding the vacuole of sap is called the tonoplast</li><li>Helps maintain cell pressure, ensuring the cell remains rigid and prevents wilting of the plant</li><li>In addition to this, isolates unwanted chemicals in the cell</li></ul> Why may cells have lots of mitochondria?If the cell used lots of energy Why do some cells have villi?<div><ul><li>To extend away from the main cell<br></li><li>This increases the surface area for absorption<br></li><li>e.g. in the epithelial cells of the small intestine</li></ul></div> What is a group of cells called?tissue What is a tissue?A group of (specialised) cells that works together to carry out a specific function What are organs?Groups of different tissue that work together to perform certain functions<br> What is an organ system?A group of organs that works together to perform a function in a multicellular organism Describe the structure and function of the cell wall of prokaryotic cells:<br><div><ul><li>F: Retains the structure of the cell, prevents it from changing shape</li><li>S: Made of murein polymer</li><li>Murein is a glycoprotein</li><li>A glycoprotein is a protein with a carbohydrate attached</li></ul></div> What is a feature of a bacteria cell, not necessarily found in all prokaryotic cells?<div><ul><li>A capsule containing secreted slime</li><li>This protects the bacteria form attack by immune system cells</li></ul></div> Describe the plasmids found in prokaryotic cells:<br><ul><li>Small loops of DNA<br></li><li>Contain antibiotic resistance genes amongst others</li><li>Able to be passed between prokaryotes</li><li>Some have several plasmids, others have no plasmids</li></ul> Describe the DNA of prokaryotic cells: [4]<br><ul><li>No nucleus is present<br></li><li>DNA is free in the cytoplasm</li><li>Circular DNA</li><li>Not attached to any histone proteins<br></li></ul> Describe the flagellum of prokaryotic cells:<br><div><ul><li>Long whip-like structures<br></li><li>Rotate to enable to prokaryotic cell to travel<br></li><li>Not present in all, some have several</li></ul></div> Describe the structure of a virus:<ul><li>Contain core genetic material, as RNA or DNA<br></li><li>Have a ‘capsid’ which is a protein coat</li><li>Attachment proteins stick out from the edge of the capsid to allow the virus to attach to a host cell</li></ul> Viruses have no...<ul><li>No plasma membrane</li><li>No ribosomes</li><li>No cytoplasm</li></ul> Viruses are smaller than..bacteria How do prokaryotic cells replicate?<div>By binary fission</div><div>Cells split to make two daughter cells</div> Describe the process of cell replication by binary fission"<ul><li>Circular DNA and plasmid(s) replicate<br></li><li>The DNA group is only replicated once</li><li>Plasmids can be replicated several times</li><li>The cell grows / cytoplasm extends</li><li>DNA loops travel to opposite ends of the cell</li><li>The cytoplasm starts the division process by forming new cell walls</li><li><b>The cytoplasm fully divides</b> to produce two daughter cells, each with one copy of circular DNA, but varying amounts of plasmids</li></ul><div><img src=""paste-e0d8c3e3c5660a685e284147e948fb90e390398e.jpg""><br></div>" What is magnification and how is it calculated?<div>How much bigger the image is that the actual sample/specimen</div><div><br></div><div>Magnification = size of image / size of object</div> What is resolution?<div>How well can a microscope distinguish between two points that are close together<br></div> What is an optical microscope?<ul><li>Light is used to form an image<br></li><li>Maximum resolution = 0.2 micro-metres</li><li>Cannot view organelles such as ribosomes, endoplasmic reticulum or lysosomes, since these are smaller than the 0.2 micrometer resolution</li><li>Only the nucleus and perhaps mitochondria are visible</li><li>Maximum magnification = x 1500</li></ul> What are transmission electron microscopes?<div>Transmission Electron Microscopes (TEM)</div><div><br></div><div><ul><li>Electromagnets focus a beam of electrons that gets transmitted through the specimen</li><li>The variations in density of the specimen cause varying amount of electrons to be absorbed</li><li>Denser areas appear darker</li><li>Internal structures of organelles can be observed</li><li>Only able to be used on thin specimens</li></ul></div> What are scanning electron microscopes?<br><ul><li>A beam of electrons is scanned across the specimen</li><li>Electrons are knocked off of the specimen</li><li>The electrons are gathered in a cathode ray tube, and an image is formed</li><li>Images have capability of being 3D</li><li>The images show the surface of the specimen</li></ul> Compare SEMs and TEMs:<div><ul><li>SEMs can be used on thick specimens, TEMs can only be used on thin specimens</li><li>SEMs give lower resolution images than TEMs</li><li>SEMs produce 3D images</li></ul></div> What is cell fractionation?The separation of organelles from the rest of the cell, before examining them under an electron microscope What are the three stages of cell fractionation?<ol><li>Homogenisation - Breaking cells<br></li><li>Filtration - Removing large debris</li><li>Ultracentrification - Separating the organelles</li></ol><div></div> Draw a labelled diagram showing the cell cycle:"<img src=""paste-3e707893bd9a19c54131d84e6cd95f01a64afccd.jpg"">" What is the M phase in the cell cycle?<br>Involves mitosis and cytokinesis<br> What is interphase in the cell cycle?<br>"<div>The period of cell growth</div><div>Split into three stages:</div><div><span style=""color: rgb(32, 33, 36);""><br></span></div><div><span style=""color: rgb(32, 33, 36);"">➤</span>G1 = proteins synthesised</div><div><span style=""color: rgb(32, 33, 36);"">➤ S phase = DNA replicates</span></div><div><div><div><div><span style=""color: rgb(32, 33, 36);"">➤ G2 = organelles grow and divide</span><br></div><div><span style=""color: rgb(32, 33, 36);"">➤ Two copies of DNA remain joined at the centromere</span><span style=""color: rgb(32, 33, 36);""><br></span></div><br></div></div></div><div><div></div><div><img src=""paste-eeb69383f271cdc3a4ca2dc601987e16db049fce.jpg""><br></div></div>" What regulates the cell cycle?<br>"<div>Checkpoints</div><div>These involve checks to see if the next stage can go ahead</div><div><br></div><div><img src=""paste-73d84bec22eabd522fdfbf9eccc0184b709f14d7.jpg""><br></div>" What are the 4 stages of mitosis?<br><ol><li>Prophase<br></li><li>Metaphase</li><li>Anaphase</li><li>Telophase</li></ol> What is prophase in mitosis?<br>"<div><br></div><div>➤ DNA condenses into chromosomes <div>➤ Chromosomes shorten/coil <div>➤ Nuclear envelope breaks down and centrioles move apart to opposite poles<br></div><div>➤ Spindle fibres develop from centrioles </div></div><div><img src=""paste-f75609b28a2e644a9a9081abe0ca1a6b015eac16.jpg""><br></div></div><div><br></div>" What is metaphase in mitosis?<br>"➤ Chromosomes line up at the equator of the cell <div>➤ Spindle fibres attach to the centromeres on the chromosomes</div><div><img src=""paste-d4bbd07afde4bd6d0088d4cda7e07edcff7e1cab.jpg""><br></div>" What are chromatids, and what is a centromere?<br><div>A chromatid is a separate strand of a chromosome (1 of 2 strands)</div><div><br></div><div>The strands are joined in the middle by a centromere</div> What is anaphase in mitosis?<br>"<ul><li>Centromeres divide<br></li><li>This separates each sister pair of chromatids<br></li><li>Protein fibre spindles contract, and the chromatids are moved to opposite ends of the cell</li></ul><div><br></div><div><img src=""paste-38916e0d8e14388908f6b5acd5195b4efb4fa81d.jpg""><br></div>" What is telophase in mitosis?<br>"<div>➤ Nuclear envelope and nucleolus reform<div>➤ Spindle fibres disintegrate<br></div><div>➤ Chromosomes reach poles and become indistinct </div><div><img src=""paste-b025b63d69eb9c2dfdbd01b001614e8d8e4a6dfb.jpg""><br></div></div><div><br></div>" Describe the process of observing cells using an optical microscope:<ul><li>Clip the pre-prepared slide onto the stage<br></li><li>Choose the lowest powered objective lens </li><li>Raise the slide to just below the objective lens using the coarse adjustment knob</li><li>Look through the eyepiece that contains the ocular lens ad use the coarse adjustment knob to move the stage downwards to focus the image</li><li>Use the fine adjustment knob to further adjust the focus</li><li>Adjust until the image is clear</li><li>Swap to a higher powered objective lens if needed</li></ul> What is the mitotic index?<div>The proportion of cells that are undergoing mitosis</div><div><br></div><div>Mitotic Index = Number of cells with visible chromosomes / Total cells seen</div> Describe how you can calculate the size of cells:<ul><li>Fit an eyepiece graticule onto the eyepiece of the microscope</li><li>Add the stage micrometer to the stage of the microscope</li><li>Calibrate the eyepiece graticule using the stage micrometer</li></ul><div>STEPS:</div><div><ol><li>Line up the eyepiece graticule and stage micrometer</li><li>Work out the size of 1 division on the eyepiece graticule at that <b>particular magnification</b></li><li>Calculate the size of the object based on the scale</li></ol></div> What are artefacts in terms of microscopes?<div>Artefacts are any objects that can be seen down the lens of the microscope that are not a part of the cell or specimen</div><div><br></div><div>E.g. bubbles of air, dust or fingerprints</div> "Name two structures in a eukaryotic cell that cannot be identified using an optical microscope: MS [2]"<div>Any two of the following:</div><div><ul><li>Mitochondrion</li><li>Ribosome</li><li>Endoplasmic Reticulum</li><li>Lysosome</li><li>Cell-surface membrane</li></ul></div> Describe how the RER is involved in the production of enzymes: MS [2]<div>The RER contains ribosomes</div><div>These make proteins, and enzymes are proteins</div> Describe how the Golgi apparatus is involved in the secretion of enzymes: MS [1]<div>Modifies the protein</div><div>OR</div><div>Packages it into the Golgi vesicles</div><div>OR</div><div>Transports it to the cell surface</div> What are the functions of the phospholipid bilayer?<ul><li>Form an impermeable barrier to water-soluble substances</li><li>Allow the cell to maintain two different concentrations on either side of it's CSM</li><li>Allows membranes to be self sealing</li></ul><div></div> What type of structure do cell membranes have?<br>A fluid mosaic structure<br> Recall the fluid mosaic model for the CSM. MS [2] <br><ul><li> idea of molecules / named molecules <u>moving</u> = Fluid;</li><li>idea of both <u>proteins and phospholipids</u> = Mosaic;</li></ul> What is the role of proteins in cell membranes?<br><div>Control what enters and leaves the cell</div><div><ul><li>Protein channels allow small/charged particles through</li><li>Carrier proteins transports ions via active transport and facilitated diffusion</li><li>Proteins can act as receptors in cell signalling</li></ul></div> What is the role of glycolipids and glycoproteins in a cell membrane?<br><ul><li><b>Stabilise </b>the <b>membrane </b>due to the hydrogen bonds with the surrounding water molecules</li><li>Drugs, <b>hormones </b>and antibodies bind to glycoproteins and glycolipids</li><li>Act as cell signalling <b>receptors</b></li><li>Exist as <b>antigens</b>, on the surface for the immune system</li></ul> Describe how you can investigate the permeability of a cell membrane in the lab using beetroot:<ul><li>Cut 5 equal sized pieces of beetroot using a scalpel<br></li><li>Rinse to remove pigment on the surface after cutting</li><li>Add each piece to a test tube with 5 cm3 of water</li><li>Place each in a different temperature water bath (10, 20, 30, 40 and 50 ºC) for the same amount of time</li><li>Remove the beetroot so only coloured liquid is left</li><li>Determine the absorption of the coloured solution left using a colorimeter</li><li>High absorbance means more pigment was released</li><li>Plot on a graph, or connect the colorimeter to a computer</li></ul> How does temperature affect membrane permeability? Draw a graph:"<ul><li>Below 0ºC the phospholipids don’t <b><font color=""#ff0000"">have much energy</font> </b>and cannot move much - the membrane is rigid except for the channel proteins and carrier proteins which deform to increase the permeability. High permeability can occur if ice molecules pierce the membrane to form holes</li><li>0ºC - 45ºC means phospholipids can move around but aren’t packed close together. The membrane is only <b><font color=""#ff0000"">partially permeable</font></b>, but permeability gradually increases with temperature</li><li>Over 45ºC causes the phospholipid bilayer to begin to melt, making the membrane <b><font color=""#ff0000"">more permeable</font></b>. Water expands causing the channel membranes and carrier proteins to deform - increasing permeability</li><li><img src=""IMG_1126.jpeg""></li></ul>" What is diffusion?<div>The net movement of particles (ions/molecules) from an area of higher concentration to an area of lower concentration</div><div><br></div><div>The molecules move both ways, but there is always a net movement from high to low concentration</div> What is a concentration gradient?<div>The path from an area of high concentration to an area of low concentration</div><div><br></div><div>The particles will diffuse down the concentration gradient</div> What type of process is diffusion?<ul><li>passive</li><li>no energy required</li></ul> Why is facilitated diffusion needed?<ul><li>Larger molecules would only undergo slow diffusion<br></li><li>Charged and polar particles would diffuse slowly because they are water soluble and the centre of the phospholipid bilayer is hydrophobic</li></ul><div><br></div><div>Facilitated diffusion is when diffusion happens through carrier proteins and channel proteins</div><div>It is passive,, no energy is used</div> Describe how carrier proteins are involved in facilitated diffusion:<div>Large molecules are moved down the concentration gradient<br></div><div><br></div><div><ul><li>A large molecule attached to the carrier protein</li><li>The protein changes shape</li><li>The molecule is released on the other side of the membrane</li></ul></div> Describe how channel proteins are involved in facilitated diffusion:<br><ul><li>Channel proteins form pores in the membrane<br></li><li>Charged particles can diffuse through the pores</li><li>Different channel proteins are responsible for the facilitated diffusion of different charged particles</li></ul> How does simple diffusion depend on concentration gradient?<div>Higher concentration gradient = faster rate of diffusion</div><div><br></div><div>The difference in concentration eventually reaches an equilibrium</div> How does simple diffusion depend on thickness fo the exchange surface?<br><div>Thinner exchange surfaces give a faster rate of diffusion</div><div><br></div><div>This is because the particles don’t have to travel as far</div> How does simple diffusion depend on surface area?<br><div>Larger surface area = faster rate of diffusion</div><div><br></div><div>This is often used by specialised cells, such as microvilli</div> How does facilitated diffusion depend on concentration gradient?<br><div>Higher concentration gradient leads to faster facilitated diffusion</div> How does facilitated diffusion depend on the number of carrier/channel proteins?<br><div>If all of the carrier or channel proteins are in use, the the facilitated diffusion cannot be sped up any further</div><div><br></div><div>Greater number = faster rate of facilitated diffusion</div> What is osmosis?The diffusion of water molecules across a partially permeable membrane, from an area of high water potential to an area of lower water potential What is water potential?The likelihood of water molecules diffusion in/out of a solution<div><br></div><div><ul><li>pure water = 0</li><li>more solute, more negative value</li></ul></div> What has the highest water potential?Pure water has the highest water potential, any solution will have a lower water potential than pure water What are isotonic solutions?Solutions that have the same water potential What factors affect rate of osmosis?<ul><li>Water potential gradient<br></li><li>Thickness of the exchange surface</li><li>Surface area of the exchange surface</li></ul> What is active transport?Using energy to move molecules and ions across membranes, often against their concentration gradient Describe the process of active transport:1) Molecule/ion binds to receptors on its <b>specific carrier protein</b><div>2) <b>ATP binds </b>to the side of the protein on the inside of the cell</div><div>3) ATP is <b>broken down </b>into ADP and a phosphate molecule, causing the carrier protein to change shape</div><div>4) Carrier protein <b>release molecule</b>/ion on the other side of the membrane</div><div>5) Phosphate molecule and ADP released from the protein causing it to return to its <b>original configuration</b></div><div>6) ADP and phosphate <b>recombine </b>to make ATP during respiration </div> What are co-transporters?<div>A type of carrier protein</div><div><ul><li>Bind to two molecules at a time</li><li>The molecules join and travel together</li><li>The concentration gradient of molecule 1 is used to transport molecule 2 against its concentration gradient</li></ul></div> What are 3 factors that affect the rate of active transport?<ul><li>Speed of carrier proteins<br></li><ul><li>Faster action = faster active transport</li></ul><li>Number of carrier proteins present</li><ul><li>More present = faster active transport</li></ul><li>Rate of respiration of the cell</li><ul><li>Slower = less ATP</li><li>Less ATP = slower active transport</li><li>Not sufficient ATP = no active transport</li></ul></ul> Explain the process of glucose entering the ileum epithelium by cotransport:<div><ul><li>Sodium ions are actively transported out of the ileum epithelial cells and into the blood - using he sodium-potassium pump<br></li><li>This leads to there being a higher concentration of sodium ions in the lumen of the ileum</li><li>Sodium ions then travel down the concentration gradient into the epithelial cell via sodium-glucose co-transporter proteins</li><li>The co-transporter carries glucose into the cell along with he sodium</li><li>Concentration of glucose inside the cell therefore increases</li><li>Glucose diffuses out of the cell and into the blood down the concentration gradient</li><li>The glucose goes trough a protein channel, by facilitated diffusion</li></ul></div> "Using your knowledge of the structure of the cell-surface membrane, suggest how LDL enters the cell: MS [2]"<ul><li>The lipid is soluble (hydrophobic)<br></li><li>It enters through the phospholipid bilayer</li></ul><div>OR</div><div><ul><li>The protein part of LDL attaches to the receptor</li><li>This goes through a carrier/channel protein</li></ul></div> "Stomata close when lights are turned off. Explain the advantage of this to the plant: MS [3]"<div><ul><li>Water is lost through the stomata<br></li><li>Closure prevents/reduces water loss<br></li><li>This maintains the water content of the cells</li></ul></div> What are the four stages of an immune response?<ol><li>Phagocytes engulf pathogens<br></li><li>Phagocytes activate T-cells</li><li>T-cells activate B-cells that divide into plasma cells</li><li>Plasma cells produce antibodies for the antigen</li></ol> Describe the process of phagocytosis:1.      Phagocyte attracted by a substance / recognises (foreign) antigen<br>2.    (Pathogen)engulfed / ingested;<br>3.     Enclosed in vacuole / vesicle / phagosome;<br>4.     (Vacuole) fuses / joins with lysosome;<br>5.     Lysosome contains enzymes;<br>6.   Accept named example of enzyme (hydrolytic / lysozyme)<br>7.    Pathogen digested / molecules hydrolysed;<br>8.   small parts of pathogen also presented on the surface of the phagocyte<br> Draw a diagram of an antigen-antibody complex:"<img src=""paste-936e1c8f84cafa90a469388694bdcaaf5c79fc83.jpg"">" What is a secondary response?<ul><li>The immune system can respond fast when it recognises antigens from the same pathogen upon reinfection</li><li>Clonal selection is faster</li><li>Memory B-cells get activated to divide into plasma cells</li><li>Memory T-cells get activated to divide into T-cells to kill the cell with the antigen</li><li>Often no symptoms occur since it is such a fast response</li></ul> What are two issues with taking a vaccine orally?<div><ul><li>There enzymes in the gut may break down the oral tablet<br></li><li>The molecules of the vaccine could be too large to be absorbed into the gut<br></li></ul></div><div><br></div> What is antigenic variation and what is its consequence?<div><ul><li>When pathogens change their surface antigens<br></li><li>The immune system cannot recognise this new antigen, and the memory cells do not recognise it<br></li><li>A primary response must occur, which takes time and gives the individual symptoms<br></li></ul></div> How do countries combat the antigenic variation amongst influenza:<div><ul><li>Different strains arise every year<br></li><li>New vaccines are developed and chosen every year<br></li><li>Governments and health authorities have vaccinator programmes for the most effective vaccine that year<br></li></ul></div> What is an ELISA Test used for?Used to see if patients have antibodies for certain antigens What is AIDS?<div><ul><li>The immune system deteriorates and eventually fails<br></li><li>Those with AIDS are vulnerable to other infections such as pneumonia<br></li></ul><div><br></div></div> How does HIV infect a host?<div><ul><li>Infects and kills helper T-cells (the host cells)<br></li><li>Their role in the immune response is stopped<br></li><li>AIDS occurs when the number of helper T-cells in the body reaches a low level<br></li></ul></div> What organelles does the HIV require form the host T-helper cell and why?Needs the enzymes and ribosomes to enable it to reproduce How can HIV be spread?<ul><li>Unprotected sexual intercourse<br></li><li>Infected bodily fluids (such as blood)</li><li>From mother to foetus</li></ul> Give two ways in which pathogens can cause disease: MS [2]<div><ul><li>Release toxins</li><li>Kill cells</li></ul></div> <div>Do small animals tend to have a small or a large surface area : volume ratio?<br></div>Smaller animals tend to have a higher surface area:volume ratio Why do single celled organisms not require exchange systems?The substances can diffuse directly through the cell-surface membrane because there are only small distances to be travelled Why do multi-cellular organisms require exchange systems? [3]<div><ul><li>Cells deep within the body; large diffusion distance</li><li>Larger animals have a lower SA:V ratio; small surface area for diffusion</li><li>High demand for oxygen and to remove CO<sub>2</sub> <br></li></ul></div> What are the two main factors that affect heat exchange?<ul><li>Body size<br></li><li>Body shape</li></ul> How does the size of an organism affect heat exchange?<div><ul><li>Rate of heat loss is dependent on surface area of the organism</li><li>Large volumes tend to mean small surface areas, so it is harder for large animals to lose heat and easier for small animals that will have a higher surface area:volume ratio</li><li>Small animals therefore require a high metabolic rate for them to stay warm</li></ul></div> <div>How does the shape of an organism affect heat exchange?<br></div><div><ul><li>Compact shape means a small surface area compared to volume, and heat loss is minimised</li><li>Some features (such as ears) can increase surface area and so increase heat loss</li><li>This can be an adaptation for certain animals depending on their environment</li></ul></div> How does water loss depend on SA:volume ratio?<div><ul><li>Animals that have a high SA:Volume ratio tend to lose more water because it will evaporate for their surface</li><li>This may lead to kidney adaptations to prevent such a large water loss in urine</li></ul></div> How are animals in cold regions adapted to keep up their high metabolic rate?<div><ul><li>They are adapted to eating high energy seeds and nuts as their primary food source</li><li>They may also have fur for insulation</li></ul></div> <div>How are animals in hot environments adapted for effective heat loss?</div>Large organisms in hot regions have slow heat loss, so they increase their surface area with large ears (African bat-eared fox and elephant) for example <div>In what two ways are gas exchange surfaces typically adapted?</div><div><ul><li>Large surface area<br></li><li>Thin surface (a few cells thick, sometimes only one)</li></ul></div><div>This gives a steep concentration gradient across the exchange surface</div> <div>Describe the gas exchange system found in fish.</div><div>Gills are used for gas exchange in fish</div><ul><li>There is a lower concentration of oxygen in water than in air - not an optimal contraption gradient</li><li>Oxygenated water enters the fish through its mouth</li><li>Gills are made of gill filaments (thin plates)</li><li>Gill filaments provide a large surface area</li><li>Gill filaments are covered in lamellae to further increase surface area</li><li>Lamellae have lots of blood capillaries and a thin surface layer to optimise the rate of diffusion</li></ul> <div>How do insects exchange gases?</div>Simple diffusion through their tracheae How does air move into the trachea in insects?Through pores on the surface of the trachea called spiracles <div>How does air get from the trachea to individual cells in insects?</div>The trachea tend to branch off into smaller tracheoles with thin permeable walls that allow the oxygen to diffuse directly into the cells <div>How is carbon dioxide removed from cells in an insect?</div>Moves down the concentration gradient towards the spiracles (holes in the trachea) to then be released into the atmosphere <div>How do dicotyledonous plants exchange gases?</div><ul><li>At the surface of mesophyll cells<br></li><li>They are adapted to have a large surface area<br></li><li>Gases move in and out of many holes in the epidermis called stomata</li><li>Stomata are able to open and close to control the exchange of gases</li><li>Stomata can close if the plant is losing too much water</li></ul> <div>What controls the opening and closing of stomata?</div>Guard cells  What are the adaptations of insects for water loss? [3]<ul><li>close their spiracles</li><li>hairs around spiracles</li><li>waxy cuticle</li></ul> <div>How do plants adapt if they find themselves losing too much water?</div><ul><li><div>Guard cells lose water and become flaccid</div></li><li><div>This causes the guard cells to close the stomata</div></li></ul> <div>What are xerophytes?</div>Plants that are adapted for living in warm/windy habitats where water is easily lost <div>Why do humans need lungs?</div><div><ul><li>It is the human gas exchange system</li><li>Oxygen is taken in, for use in respiration</li><li>Carbon dioxide is removed from respiring cells</li></ul></div> <div>Where does air enter when humans breathe in?</div>Enters in the trachea <div>What does the trachea split into?</div>The trachea splits into two bronchi, with on bronchus leading to each lung What do bronchi split into?Bronchi split into small bronchiole tubes What are found at the end of bronchioles?Alveoli air sacs, where gaseous exchange occurs What are the two stages of human ventilation?<ul><li><div>Inspiration</div></li><li><div>Expiration</div></li></ul> What are alveoli surround by?A network of capillaries that provides a lot of blood flow In what 3 ways are alveoli adapted for gas exchange?<div>Thin exchange surface</div><div><ul><li>One cell thick alveolar epithelium</li><li>Short diffusion pathway</li></ul><div>Large surface area</div></div><div><ul><li>Large number of alveoli</li><li>Large total surface area used for gas exchange</li></ul><div>Ventilation</div></div><div><ul><li>Intercostal muscles / diaphragm contract to cause pressure change, leading to ventilation</li><li>Increased conc of O2 maintains conc gradient</li></ul></div> <div>What is tidal volume?</div>The volume of air in each breath at rest What is ventilation rate?The number of breaths per minute What is forced expiratory volume?FEV1 is the maximum volume of air that can be breathed out in 1 second What is forced vital capacity?FVC is the maximum volume of air that it is possible to breathe out forcefully from the lungs after a deep breath How does pulmonary tuberculosis (TB) affect breathing?<ul><li>When infected with TB, the immune system build a wall around the tuberculosis bacteria in the lungs<br></li><li>This forms tubercles</li><li>The infected tubercle tissue dies</li><li>The lung is damaged, which is responsible for gaseous exchange</li><li>Tidal volume is reduced</li><li>Less air is brought in with every breath</li><li>Patients must breath faster</li><li>Causes a cough, chest pain, blood, mucus, fatigue </li></ul> How does fibrosis affect breathing?<br><ul><li>Formation of scar tissue in the lungs<br></li><li>Can lead to infection upon exposure to asbestos or dust</li><li>Scar tissue is less elastic and thicker than regular lung tissue with means the tidal volume is reduced</li><li>The rate of gaseous exchange is reduced</li><li>Diffusion is slower</li><li>Symptoms are<b> shortness fo breath, fatigue, dry cough, chest pain, weakness</b></li></ul> How does asthma affect breathing?<br><ul><li>Airways are irritated and inflamed</li><li>Often due to an allergic reaction to pollen/dust</li><li>Smooth muscle lining the bronchioles contracts and causes lots of mucus to be produced</li><li>Airways are constricted and breathing is difficult, meaning air flow in/out of the lungs is reduced</li><li>FEV1 is reduced</li><li>Causes wheezing, tight chests, shortness of breath</li><li>Treatment involves use of an inhaler, to cause the smooth muscle lining the bronchioles to relax</li></ul> How does emphysema affect breathing?<div><br></div><ul><li>The loss of elastin means the <b>alveoli are unable to recoil and expel air</b></li><li>The alveoli walls are also destroyed which <b>reduces their surface area</b>, so rate of gaseous exchange decreases</li><li>It causes shortness of breath and wheezing</li><li>The ventilation rate has to increase to increase that amount of air that reaches the lungs</li></ul> <div>What are risk factors?</div>Factors that increase a persons chances of getting a disease What is a correlation?<div>A link between two things</div><div><br></div><div>E.g. a risk factor correlated to frequency of a disease</div> Describe and explain the mechanism that causes forced expiration. MS [4]<ul><li>Internal intercostal muscles contract<br></li><li>Diaphragm muscles relax, external intercostals relax<br></li><li>The volume of the thoracic cavity decreases<br></li><li>Air gets pushed down the pressure gradient</li></ul> Describe how oxygen in the air reaches capillaries surrounding alveoli in the lungs. MS [4]<ul><li>Trachea and bronchi<br></li><li>The oxygen goes down the pressure gradient</li><li>And down the diffusion gradient</li><li>Across the alveolar epithelium</li></ul> Describe a method you could use to find the surface area of a leaf: MS [3]<div><ul><li>Draw around a leaf on a piece of graph paper</li><li>Count the number of squares</li><li>Multiply by 2 (for top and bottom of the leaf)</li></ul></div> Describe two adaptations of the structure of alveoli for efficient gas exchange: MS [2]<ul><li>Thin walls/cells</li><li>Large total surface area</li></ul> Why must large food biological molecules (such as starch and proteins) be broken down?They are too large to be absorbed into the blood from the gut, because they cannot diffuse across the cell membranes What is amylase?<div>A digestive enzyme used to catalyse the conversion of the polysaccharide starch to a smaller sugar disaccharide, called maltose</div><div><br></div><div>This involves the hydrolysis of the glycosidic bonds in starch</div> Where is amylase produced?<div>Produced by salivary glands for release into the mouth</div><div><br></div><div>Produced by the pancreas that released amylase into the small intestine</div> What are membrane-bound disaccharides?<div>Enzymes found attached to cell membranes of epithelial cells that line the ileum (the final part of the small intestine)</div> What is the disaccharidase for the disaccharide maltose, and what are the monosaccharide products?<div>Disaccharide = maltase</div><div>Monosaccharide products = glucose + glucose</div> " <div>What is the disaccharidase for the disaccharide sucrose, and what are the monosaccharide products?</div>"<div>Disaccharide = sucrase</div><div>Monosaccharide products = glucose + fructose</div> What is the disaccharidase for the disaccharide lactose, and what are the monosaccharide products?<br>Disaccharide = lactase<div>Monosaccharide products = glucose + galactose</div> How are monosaccharide transported across cell membranes of the epithelial cells ileum epithelial cells?Transported by specific transporter proteins What do lipases do?<div><ul><li>Lipases are enzymes that catalyse the breakdown of lipids into monoglycerides and fatty acids</li><li>The ester bonds in the lipids are hydrolysed</li></ul></div> Where are lipases made?In the pancreas, but they work in the small intestine <div><b>Bile salts...</b></div><div>produced by:</div><div>stored in:</div><div>function is to:</div><ul><li>Produced by the liver</li><li>Stored in gallbladder</li><li>Emulsify lipids (making the lipids form small droplets)</li></ul> Why are bile salts required in the digestion of lipids?<div>The bile salts emulsify the lipids</div><div>This gives them a bigger surface area</div><div>This increases the area that the lipases can work on</div> How is glucose absorbed after it is made as a product of digestion?Glucose gets absorbed by co-transport using sodium ions, via a co-transporter protein How is galactose absorbed after it is made as a product of digestion?<br>Galactose gets absorbed by active transport using sodium ions, via a co-transporter protein How is fructose absorbed after it is made as a product of digestion?<br>Absorbed via facilitated diffusion by a transporter protein How are amino acids and fatty acids absorbed after being made as a product of digestion?<div>Sodium ions are actively transported out of the epithelial cells and into the ileum</div><div><br></div><div>They diffuse into the cells again via sodium dependent transporter proteins in the epithelial membranes - whilst carrying the amino acids</div> What type of cells contain haemoglobin?Red blood cells Describe the structure of haemoglobin:<ul><li>Quaternary structure protein</li><li>Made of four polypeptide chains</li><li>There is a haem group in each chain contains an iron ion which causes the red colour</li></ul> What type of reaction is the joining of oxygen and haemoglobin?<div><br></div><div>Write out the equation. </div>"A reversible reaction:<img src=""paste-906a1edea0b261037b65b3c91a160d8740c81a3b.jpg"">" How does haemoglobin’s affinity for oxygen depend on the partial pressure of oxygen?"Oxygen will load on haemoglobin when there is a high <span style=""font-style: italic;"">p</span>O2 to form oxyhaemoglobin" How does haemoglobin’s likelihood to unload oxygen depend on the partial pressure of oxygen?<br>"Oxyhaemoglobin will unload oxygen when there is a lower <span style=""font-style: italic;"">p</span>O2" "What happens to <span style=""font-style: italic;"">p</span>O2 when cells respire?""<span style=""font-style: italic;"">p</span>O2 is lowered" Draw a dissociation curve for adult human haemoglobin:"<img src=""paste-b55416b504f618dcfa513a8aa644ab5b3942100d.jpg""><ul><li>High <span style=""font-style: italic;"">p</span>O2 comes with high haemoglobin affinity for oxygen, high saturation</li><li><span style=""font-style: italic;"">p</span>O2 low means low affinity for oxygen, low saturation</li></ul>" How does carbon dioxide partial pressure affect oxygen unloading from haemoglobin? What effect is this?"<img src=""paste-4130a952630e28821a8ff69d9d2b24e6c5d3f0f9.jpg""><ul><li>Cells respire and raise <span style=""font-style: italic;"">p</span>CO2 </li><li>The rate of oxygen unloading increases, the dissociation curve shifts right</li><li>More oxygen is released</li><li>This is the Bohr effect</li></ul>" How does haemoglobin of an organism adapt to the environment?"<ul><li>Organisms in environments with low concentrations of oxygen will have haemoglobin with high affinity for oxygen (to the left of the human curve)<br></li><li>Organisms that are active and have a high oxygen demand will have lower affinity (right of human curve)</li></ul><div><img src=""paste-5b0d0a9d1e0002168c2cedcbc28fca2ed13356c8.jpg""><br></div>" List the main specialised transport system in mammals:The circulatory system What is in the circulatory system?Various blood vessels, and the heart What does blood transport around the body?<ul><li>Digestion products<br></li><li>Hormones<br></li><li>Respiratory gases<br></li><li>Metabolic waste<br></li></ul> Which two vessels give the heart its own blood supply?The left and right coronary arteries What is the function and adaptations of arteries?<ul><li>Carry blood form the heart to the rest of the body<br></li><li>Carry oxygenated blood (except pulmonary arteries carry deoxygenated blood to the lungs)</li></ul><div><b>Adaptations:</b></div><ul><li>Thick muscular walls</li><li>Elastic tissue enables stretch and recoil</li><li>These allow high pressure in the arteries</li><li>The inner lining called the endothelium is folded and can stretch</li></ul> What do arteries divide into?Arterioles What are veins?<ul><li>Return blood to the heart<br></li><li>Low pressure transport</li><li>Carry deoxygenated blood</li><li>Except, pulmonary veins carry oxygenated blood from heart to lungs</li></ul> What do arterioles branch into?Arterioles branch into capillaries, the smallest type of blood vessels What are capillaries used for?Capillaries are used for allowing oxygen and glucose to diffuse into cells What is tissue fluid?<ul><li>Fluid surrounding cells in tissues<br></li><li>Made form small molecules from blood plasma<br></li><li>Consists of oxygen, water, nutrients</li><li>Does not contain red blood cells or big proteins - these cannot fit through the capillary walls</li></ul> Why is tissue fluid useful for cells?<div>The cells take in oxygen and nutrients from tissue fluid</div><div>Metabolic waste is released into the tissue fluid</div> How do substances move out of the capillaries into the tissue fluid?ultrafiltration<div><br></div> What happens to excess fluid during the pressure filtration process that forms tissue fluid?It is drained into the lymphatic system "Label this diagram of the heart:<div><br></div><div><br></div><div><img src=""paste-5b0afd72fd0a5c32f4c15f5b542937262ddb3dbb.jpg""><br></div>""<img src=""paste-48c34b555fa493d75ee28df8e4aecf415b06b56e.jpg"">" Why does the heart have valves?<br>To prevent blood from flowing the wrong way<br> What are atrioventricular valves?<br><div>Heart valves that link the atria to the ventricles</div><div>They stop blood from flowing the wrong way</div> What is an atheroma and how is it formed?"<ul><li>High blood pressure can damage the inside endothelium of an artery<br></li><li>White blood cells and lipids form fatty streaks by clumping together</li><li>These build up over time</li><li>Eventually an <b>atheroma </b>is formed (build up of fatty plaque)</li></ul><div><img src=""H2-image-p21.jpg""><br></div>" What is Coronary heart disease?<ul><li>CHD<br></li><li>A cardiovascular disease<br></li><li>Arteries get full of atheromas and blood flow to the heart is restricted<br></li><li>This can cause s myocardial infarction</li></ul> What is an aneurysm?<div>A disease affecting arteries</div><div><ul><li>Arteries are damaged, weakened and narrowed</li><li>Blood pressure increases</li><li>Blood causes a swelling where inner layers are pushed past out elastic’s layers</li><li>The aneurysm can burst, and cause a haemorrhage that leads to excessive bleeding</li></ul></div> What is thrombosis?<ul><li>Atheromas rupture<br></li><li>The artery wall is damaged and the surface gets rough</li><li>Platelets and fibrin protein accumulate, forming a blood clot (a blood clot = thrombus)</li><li>This leads to blockage or dislodging</li><li>Debris can cause rupture further along the artery</li></ul> What is a myocardial infarction?<ul><li>A heart attack</li><li>When coronary arteries are completely blocked, and the blood (hence oxygen) supply is cut off</li><li>Causes:</li><ul><li>Chest pain</li><li>Sweating</li><li>Breathing difficulties</li><li>Death if large areas of the heart are affected</li></ul></ul> <div>List 3 factors that increase the risk of cardiovascular disease:</div><ul><li>High blood cholesterol / poor diet<br></li><li>Smoking cigarettes</li><li>High blood pressure</li></ul> How does high blood cholesterol and poor diet lead to cardiovascular disease?<ul><li>High cholesterol leads to a higher risk of cardiovascular disease<br></li><li>Cholesterol is a contributor to the fatty deposits that caused atheromas to form</li><li>Ateromas increase blood pressure and cause blood clots</li><li>Coronary arteries get blocked</li><li>This can cause heart attacks</li><li>High saturated fat diets can cause high blood cholesterol</li><li>High salt diets increase risk of cardiovascular disease as it leads to high blood pressure</li></ul> How does high blood pressure lead to cardiovascular disease?<ul><li>High blood pressure can likely cause damage to the walls of arteries<br></li><li>The damage increases the risk of atheroma formation</li><li>Atheromas can cause blood clots</li><li>Blood clots can lead to heart attacks</li><li>Reduced risk by not being overweight and by exercising and avoiding large alcohol intakes</li></ul> What is the role of xylem tissue?<div>Transports water and mineral ions in solution</div><div><br>The substances move up the plant from the roots to the leaves</div> Recall the structure of xylem vessels [5]"<div style=""text-align: center;""><br></div><ul><li>Transport water and ions</li><li>Long tube like structures</li><li>Formed from dead cells</li><li>No end walls</li><li>An undisturbed pathway for transportation</li></ul>" What is transpiration?<div>The way water is lost from plants through open stomata</div><div><br></div><div>It moves down the concentration gradient, because there is a lower concentration of water in the air than in the plant</div> What are four factors that affect transpiration rate?<ul><li>Light<br></li><li>Temperature<br></li><li>Humidity<br></li><li>Wind</li></ul> Draw a diagram of a potometer:<br>"<img src=""paste-489a30bfd60d608019a849354163fea576f09400.jpg"">" <div>Describe how you use a potometer to estimate transpiration rate:</div>"<ul><li>Cut a shoot underwater so no air can escape from the xylem - make the cut at a slant to increase water intake surface area</li><li>Set up the potometer underwater - insert the shoot</li><li>Remove the structure form underwater once assembles and water and air tight</li><li>Dry the leaves</li><li>Shut the tap</li><li>Remove the capillary tube end until a single air bubble forms - put the tube back in the water</li><li>Record start position of the air bubble and set a stop watch</li><li>Use the rate of air bubble movement as an estimate for the transpiration rate<img src=""paste-45360a5f9c9d0b531f609ae1e99d88d18de18cce.jpg""></li></ul>" What does phloem transport?<ul><li>Solutes (dissolved substances)<br></li><li>E.g. sucrose<br></li><li>Phloem is a tube like structure formed from cells called sieve tube elements<br></li><li>Companion cells assist</li></ul> Describe the structure of phloem tissue:<ul><li>Sieve tube elements for a tube that is used to transport the solutes</li><li><b>Sieve tube element</b><ul><li>Stacked on top of each other</li><li>No nucleus, little cytoplasm, P-proteins</li><li>Large pores in end walls → Sieve plates with cytoplasm passing from element to element</li><li>Smaller pores in side walls with strands of cytoplasm (plasmodesmata)</li></ul></li><li><b>Companion Cells</b></li><ul><li>Smaller cells, with cytoplasm and organelles</li><li>Each controls activity of adjacent sieve tube element</li><li>Provides energy for active transport</li></ul></ul> What is translocation?<ul><li>The movement of solutes to the location where they are needed<br></li><li>Occurs in the phloem, and requires energy<br></li><li>The solute moves from source to sink</li></ul> What is a solute source?<div>Where the solute is made</div><div>The solute is in high concentration here</div> What is a solute sink?<div>Where the solute is used</div><div>The solute is in low concentration here</div> How is it always ensured that there is a concentration difference and the sink always has a lower concentration than the source?Sucrose is actively unloaded into cells at the sink end What are four experiments that support the mass flow theory? [4]<div><ul><li>Radioactive tracing</li><li>Aphids</li><li>Ringing </li><li>Metabolic Inhibitor </li></ul><div><br></div></div><div>Context:</div><div><ol><li>Carbon-14 can be used as a <b>radioactive tracer </b>to track organic substance movement</li><li>Phloem pressure can be investigated using <b>aphids </b>to analyse sap flow. The sap flows out fastest near the leaves when the surface is pierced, so this indicates there is a pressure gradient</li><li>A <b>metabolic inhibitor </b>put into the phloem will stop translocation, which suggests active transport is involved</li><li>Removing a <b>ring of bark</b> form a woody stem makes a bulge above the ring. The bulge will have a higher concentration of sugars than below the ring - suggesting sugar flows downwards</li></ol></div> <div>Describe how translocation can be demonstrated experimentally using radioactive tracers:</div><div>Using radioactive tracers:</div><div><ul><li>Tend to use carbon-14 radioactive tracer</li><li>Radioactive carbon is tied to organic substances in the leaf, such as sugar, which will then move around the plant during translocation</li><li>Autoradiography is used to track the substance’s movement around the plant</li><li>The plant is place on a photographic film, and radioactive substance turns black</li><li>Source to sink translocation can be seen in the plant</li></ul></div> State and explain the ways in which sieve cells are adapted for mass transport: MS [5]<ul><li>No/few organelles<br></li><li>Little cytoplasm</li><li>Hollow</li><li>Large vacuole</li><li>Thick walls</li></ul><div><ul><li>Means more and easier flow, and stronger resistance to pressure</li></ul></div> Explain 2 ways in which companion cells are adapted for the transport of sugars between cells: MS [4]<br><div><ul><li>Mitochondria are present to release energy<br></li><li>For active transport</li></ul></div><div><ul><li>Ribosomes make proteins</li><li>These are needed for carrier proteins / enzymes</li></ul></div> Describe how a high pressure is produced in the leaves of plants: MS [3]<ul><li>Water potential becomes lower<br></li><li>So water enters phloem by osmosis</li><li>And the large volume of water increases pressure</li></ul> "<div style="""">Contrast the processes of facilitated diffusion and active transport: MS [3]<br></div>"<ul><li>Facilitates diffusion involves channel/carrier proteins but active transport only involves carrier proteins<br></li><li>Facilitated diffusion doesn’t use ATP - it is passive, whereas active transport is active and uses ATP</li><li>Facilitates diffusion take place down a concentration gradient, whereas active transport can occur against a concentration gradient</li></ul> What is the function of the coronary arteries? MS [2]<div>To carry oxygen and glucose</div><div>To the heart muscle</div> "The rise and fall in blood pressure in the aorta is greater than in the small arteries. Suggest why: MS [3]"<div>The aorta is close and directly linked to the heart</div><div>The aorta has elastic tissue</div><div>The aorta can stretch/recoil</div> High blood pressure leads to an accumulation of tissue fluid. Explain how: MS [3]"<ul><li>High blood pressure = high hydrostatic pressure<br></li><li>Increases outward pressure from (arterial) end of capillary / reduces inward pressure at (venule) end of capillary<br></li><li>More tissue fluid is formed / less tissue fluid is reabsorbed</li></ul>" Describe nuclear eukaryotic DNA:<ul><li>Eukaryotic cells have linear DNA molecules that exists as chromosomes<br></li><li>Chromosomes exist in the nucleus</li><li>DNA molecules are wound up so they can fit in the nucleus - DNA is wound into histones</li><li>Histone proteins support DNA</li><li>A compact chromosome is made by coiling up the DNA and protein extremely tightly</li></ul> Describe the DNA of mitochondria and chloroplasts:<ul><li>They have their own DNA<br></li><li>The DNA is circular and shorter than DNA molecules found in the nucleus</li><li>This DNA is not associated with histone proteins</li></ul> What is a gene?A gene is a base sequence of DNA that codes for the amino acid sequence of a polypeptide or a functional RNA.  What is a triplet in a gene?A sequence of bases found in a gene that codes for 1 amino acid What is the genome of a cell?The complete set of genes in the cell What two things can genes code for?Polypeptides and Functional RNA What are introns?<div>Sections of DNA that don’t code for amino acids</div> What are exons?Sections of DNA that code for amino acids What are alleles?Different forms of the same gene How many chromosomes do humans have?46 total chromosomes, found as 23 pairs of chromosomes What is messenger RNA (mRNA)?<ul><li>Made during transcription</li><li>Carries the genetic code from the DNA to ribosomes</li><li>Used to make proteins during translocation</li><li>mRNA is a single polynucleotide strand</li><li>Groups of 3 adjacent bases are called codons/triplets</li></ul> What is transfer RNA (tRNA)?<ul><li>tRNA is involved in translation</li><li>Carries amino acids to the ribosomes that are then used to make proteins</li><li>tRNA is a single polynucleotide strand, folded into a clover shape</li><li>There are hydrogen bonds between specific base pairs</li><li>There is a specific sequence of three bases at the end called an anticodon, and an amino acid binding site at the other end</li></ul> What is the first stage of protein synthesis?Transcription What are the products of transcription in prokaryotes?<ul><li>mRNA is made directly from DNA without the need for splicing<br></li><li>This is because there are no introns in prokaryotic DNA</li></ul> " <div>What is the second stage of protein synthesis?</div>"Translation What is genetic code?The sequence of base triplets (codons) in mRNA that code for specific amino acids What does it mean to say that the code in genetic code is ‘non-overlapping’?<div>The triplets are read separately</div><div>Base triplets don’t share any bases</div> What does it mean to describe genetic code as ‘degenerate’?"<div></div> <div><div>There are more possible combinations of triplets than there are amino acids</div><div><br></div><div>There are 20 amino acids, but 64 possible triplets</div><div><br></div><div>This means there are <b>different triplets that exist that code for the same amino acid</b></div></div>" What are start and stop signals?Triplets that are used to start and stop protein production What does it mean to say that genetic code is ‘universal'?The same specific base triplets code for the same amino acids in all living things What is meant by genetic diversity? MS [1]The number of different alleles of each gene <div>Scientists have produced a monoclonal antibody that stops growth factor stimulation acting on tumours.</div><div><br></div><div><div>Use your knowledge of monoclonal antibodies to suggest how this antibody stops the growth of a tumour: MS [3]<br></div></div><ul><li>The antibody has a specific tertiary structure<br></li><li>This shape is complimentary to a receptor protein<br></li><li>It prevents the growth factor binding to the receptor</li></ul> <div>Suggest two reasons why populations might show very low levels of genetic diversity: MS [2]</div><ul><li>May be a small population (genetic bottleneck)<br></li><li>The population may have started with a small number of individuals (founder effect)</li><li>Inbreeding</li><li>Hunting</li></ul> "Suggest how a mutation can lead to the production of a protein that has one amino acid missing: MS [2]"<div>Loss</div><div>Of 3 bases (a triplet)</div> Name two ways in which meiosis produces genetic variation: MS [2]<ul><li>Independent segregation of homologous chromosomes<br></li><li>Crossing over</li></ul> "Not all mutations result in a change to the amino acid sequence of the encoded polypeptide. State 2 possible reasons why MS [2]"<ul><li>Degenerate code</li><li>Mutation in intron</li></ul> What are gametes?<div>Sperm in males</div><div>Eggs in females</div><div><br></div><div>Gametes have a haploid nucleus with one chromosome from each pair found in a normal cell</div> What happens to gametes at fertilisation?They fuse together to form a zygote, which will then develop into a new organism What is true about diploid cells?Each cell contains two copies of each chromosome, one form the mother and one form the father How is genetic diversity increased with gametes?<div><ul><li>Fertilisation that occurs during sexual reproduction is random</li><li>Different combinations of chromosomes are received from both parents, and the mixing of genetic material increases genetic diversity within the species</li></ul></div> What happens to chromatids in Meiosis I?Chromatids twist and cross over, to create different combinations of alleles whilst keeping the same genes Explain how independent segregation of chromosomes leads to genetic variation:<ul><li>One chromosome in a homologous pair comes form the father and one from the mother<br></li><li>Separation in Meiosis 1 is random and the combinations of chromosomes in the form daughter cells are random</li><li>This is the independent segregation of chromosomes and the shuffling leads to variation</li></ul> <div>Describe the genetics of the cells that mitosis produces vs meiosis:</div><div>Mitosis - genetically identical to parent cell</div><div><br></div><div>Meiosis - genetically different to parent cell</div> What is Down’s Syndrome caused by?<div>A chromosome mutation called non-disjunction</div><div><ul><li>Chromosomes down separate properly</li><li>Non-disjunction of chromosome 21 during meiosis</li><li>There is an extra copy of chromosome 21</li><li>One gamete cell gets an extra copy of chromosome 21, another cell gets none</li><li>The gamete with the extra copy fuses to another gamete at fertilisation</li><li>The zygote gets 3 copies of chromosome 21, instead of the usual 2</li></ul></div> What are the three main types of errors that can occur causing a change in a DNA base sequence?<ul><li>Substitution - a base is swapped with another</li><li>Deletion - a base is fully deleted</li><li>Insertion - a base is added</li></ul><div>The sequence of amino acids can be altered by these changes / mutations</div> <div>What type of mutation always caused the amino acid sequence to change?</div>"<div></div> <div><b>Deletions</b>, this will cause <b>frame shift </b>of all base triplets and affect the whole sequence</div>" <div>What are mutagenic agents?</div><div>Things that increase the likelihood of the otherwise random nature of DNA mutation</div><div><br></div><div>E.g.</div><div><ul><li>UV radiation</li><li>Ionising radiation</li><li>Certain viruses</li><li>Chemicals</li></ul></div> What is a genetic bottleneck?<div>An event that causes a reduction in population since large death will occur before the individuals breed</div><div><br></div><div>The number of alleles in the gene pool is reduced, and so genetic diversity is reduced</div> How can genetic diversity of a population be increased?<ul><li>Mutation of DNA causing new alleles to be formed<br></li><li>New alleles introduced if a new population of the species migrates to the area (gene flow)</li></ul> What is the founder effect?<div>An example of genetic bottleneck</div><div><ul><li>Occurs when a few organisms start a colony</li><li>There are initially a small number of alleles</li><li>Frequency of alleles in the colony may be completely different to the frequency of alleles in the population</li><li>A rare allele that causes disease may prevail and be more expressed, or be less expressed</li><li>Occurs due to:</li><ul><li>migration</li><li>separation</li><li>religion (causing separation / no breeding)</li></ul></ul></div> Describe the process of natural selection (4):"<ul><li>Random mutation can result in new alleles of a gene.</li><li>Many mutations are harmful but, in certain environments, the new allele of a gene might benefit its possessor, leading to increased reproductive success.</li><li>The advantageous allele is inherited by members of the next generation. </li><li>As a result, over many generations, the new allele increases in frequency in the population.</li></ul><div><br></div><div><br></div>" What are the three types of adaptations?<div>Behavioural adaptations</div><div>Anatomical adaptations</div><div>Physiological adaptations</div> What are behavioural adaptations?<div>The ways an organism acts to increase its chances of survival and reproduction</div> What are physiological adaptations?<br><div>Processes in an organism that increase survival chance</div><div><br></div><div>E.g. hibernation, where metabolic rate is deliberately lowered to conserve energy</div> What are anatomical adaptations?Structural features of an organisms that increase survival chances What are the two types of natural selection?<ul><li>Stabilising selection<br></li><li>Directional selection</li></ul> What is directional selection?<div>Individuals with extreme characteristics experience increased chance of survival and reproduction</div> What is stabilising selection?<br>Individuals with characteristics towards the mean range are more likely to survive and reproduce  Why are aseptic techniques important?<div>To prevent contamination of microbial cultures</div><div><br></div><div>This can both affect experiments, and cause disease in some cases so must be avoided</div> Describe the aseptic techniques that must be deployed to prevent contamination:<ul><li>Regularly disinfect surfaces<br></li><li>Disinfect utensils</li><li>Work near a bunsen burner since microbes will rise along with the hot air</li><li>Aim to only leave the lid off for a short time</li><li>Flame the neck of a flask before opening and closing to oil any microorganisms that may be near</li></ul> What is phylogeny?<div>The study of evolutionary history of groups of organisms</div><div><br></div><div>This gives insight into relations of organisms</div> What is a phylogenetic tree?A diagram that shows how organisms are related, and has evolved from common ancestors What is taxonomy?The science of classification where organisms are named, and placed into named groups What are taxa?<div>Groups used to classify organisms</div><div>There are 8 taxa in total</div><div>A group is called a taxon</div> How are taxa arranged?<div>In hierarchy</div><div>Largest groups are at the top</div><div>Smallest groups are at the bottom</div> What are the three largest taxa?<div>The three domains</div><div>These are:</div><div><ul><li>Eukarya</li><li>Bacteria</li><li>Archaea</li></ul></div> What is the binomial system used for nomenclature of organisms?<div><ul><li>A Latin name with two parts is given</li><li>The first part is the genus name, with a capital letter</li><li>The second part is the species name with a lowercase letter</li><li>Names are in italics, or underlined when hand written</li></ul></div> What is courtship behaviour?<div>Carried out by organisms with the aim of attracting a mate of the correct species</div><div><br></div><div>This may involve:</div><div><ul><li>Secreting chemicals</li><li>A dance</li><li>Colour changing</li></ul></div> How has genome sequencing clarified evolutionary relationships?<ul><li>The full DNA sequencing of organisms can be determined</li><li>Base sequences can be compared</li><li>Closely related species have high percentages of DNA base order similarity</li></ul> How has knowledge of amino acid sequences clarified evolutionary relationships?<ul><li>Related organisms have <b>similar </b>amino acid sequences in their proteins<br></li><li>Proteins are made of amino acids</li><li>The sequence of amino acids is coded for in DNA</li></ul> What are the two factors affecting genetic variation?<div>Genetic factors (genes and alleles present)</div><div>Environmental factors (food / climate / lifestyle)</div> What is required for studying variation?The population must be sampled How is a sample ensured not to be biased?The sample should be random How can it be ensured that variation found isn’t just due to chance?Results must be statistically analysed Why is the standard deviation of a sample useful?<div>Standard deviation gives an indication of variation</div><div><br></div><div>A large standard deviation means large variation</div><div>A small standard deviation means small variation</div> How can standard deviation be seen visually?<div>Using error bars</div><div>The longer the error bar, the higher that standard deviation and the greater the variation</div> What is a habitat?A place where an organism lives What is a community?All of the populations of various species that live in a habitat What is local biodiversity?The variety of species in a habitat close by. E.g. a pond or woodland What is global biodiversity?The variety of species on planet Earth What is species richness?The number of different species that are in a community How can species richness be determined?Random samples are taken from a community, and the number of different species are counted <div>What is an index of biodiversity? How can you calculate it?</div>"<div>A method used to measure biodiversity. A larger ‘d’ means there is higher biodiversity</div><div><br></div><div>N = total number of organisms of all species</div><div>n = total number of organisms of one species</div><div> Σ = ‘ the sum of '   <br></div><div><img src=""paste-17aa0e44f6b48ee9aeaaffbff96bd5838269d895.jpg""><br></div>" List 5 agricultural practices that reduce biodiversity:<ul><li>Removing hedgerows<br></li><li>Clearing large woodlands</li><li>Use of pesticides</li><li>Use of herbicides</li><li>Monoculture</li></ul> How does removing hedgerows reduce biodiversity?<ul><li>Smaller fields are made into one larger field</li><li>This destroys habitats</li><li>Biodiversity is reduced as habitats and food sources are removed</li></ul> <div>How does the clearing of woodlands reduce biodiversity?</div><ul><li>The number of trees, and the number of species of trees are both damaged<br></li><li>This means habitats are destroyed<br></li><li>The land is used for farming, but it means the species living there cannot use it for shelter and as a food source, particularly if pesticides are used<br></li><li>The species must migrate or die</li></ul> How does the use of pesticides reduce biodiversity?<ul><li>These are chemicals used to kill the organisms that feed on crops - known as ‘pests'<br></li><li>The pests are killed, and biodiversity is reduced</li><li>Species that prey on the pests lose food sources, so their species numbers could also fall</li></ul> How does the use of herbicides reduce biodiversity?<br><ul><li>These are chemicals used to kill the unwanted plants<br></li><li>The plants are killed, and biodiversity is reduced</li><li>Species that prey on the plants lose food sources, so their species numbers could also fall</li></ul> How does monoculture reduce biodiversity?<br><ul><li>Growing only one type of plant, perhaps because it has high sale demand for food<br></li><li>Biodiversity is directly reduced by doing this, particularly is other plants that are natural to the area are killed and removed to make space</li><li>Also, fewer organisms can be supported</li></ul> What are conservation schemes?<div>Programmes that aim to maintain or prevent severe reductions in biodiversity</div><div><br></div><div>E.g.</div><div><ul><li>Legal protection over endangered species</li><li>Protected areas</li><li>The Environmental Stewardship Scheme</li></ul></div> What is a species? MS [2]<ul><li>Groups of similar organisms<br></li><li>That can produce offspring that are fertile</li></ul> <div>Explain the role of independent segregation in meiosis: MS [2]</div><ul><li>To provide genetic variation<br></li><li>To allow different combinations of maternal and paternal chromosomes/alleles</li></ul> "Identify one event that occurred during division 2 but not during division 1: MS [1]<div><img src=""paste-8ced0cf6166f724d8ce1f2bf02321b8aca41e9ce.jpg""><br></div>"Separation of sister chromatids by division of the centromere "Describe what has happened during division 1 in the figure: MS [2]<div><img src=""paste-c1fe0fdd859c38d5f1031d20bb5fb843f0654661.jpg""><br></div>"<ul><li>Chromosomes are in a homologous pair<br></li><li>One of each chromosomes in the homologous pair goes into each of the daughter cells</li></ul> "<div>Describe and explain the appearance of one of the chromosomes in Cell A: MS [3]</div><div><br></div><div><img src=""paste-0b722692730b8a9d6a996f49a506148534392ee7.jpg""><br></div>"<ul><li>The chromosome is formed from two chromatids<br></li><li>Because DNA replication has occurred</li><li>Sister chromatids are held together by centromere</li></ul> What is the difference between species richness and an index of diversity? MS [1]Species richness measures only the number of different species and does not measure the number of individuals What two measurements are needed to calculate an index of diversity: MS [2]<ul><li>Number of individuals of each species<br></li><li>Total number of individuals</li></ul> "Give 5 ways in which courtship behaviour increases the probability of successful mating: MS [5]"<ul><li>Can recognise and attract the same species<br></li><li>Stimulates the release of gametes</li><li>Recognition of a mate; attract opposite sex</li><li>Indicates sexual maturity/fertility</li><li>Can form a bond so the pair can reproduce several times</li></ul> Explain what is meant by a hierarchy: MS [2]<div>Groups within groups</div><div>With no overlap between the groups</div> Explain what is meant by a phylogenetic group: MS [1]Grouped according to evolutionary links and common ancestry <div>Compare and contrast the structure <b>and</b> properties of triglycerides and phospholipids. (9 marks)</div><div><b>Similarities:</b></div><ul><li>both contain ester bonds</li><li>both contain glycerol</li><li>fatty acids on both may be unsaturated / saturated</li><li>both insoluble in water</li><li>both contain C, H, O</li></ul><div><br></div><div><b>Differences:</b></div><div><ul><li>phospholipids also contain P</li><li>tryglycerides have 3 fatty acids, whereas phosphate group have 2 fatty acids + phosphate group</li><li>tryglycerides are hydrophobic / non-polar whereas phospholipids have hydrophilic and hydrophobic region</li><li>phospholipids form bilayer in water / monolayer on surface</li></ul></div> What is a monomer? MS [1]"<font color=""#ff0000"">A repeating unit from which larger molecules are made </font>" Describe how lactose is formed and where in the cell it would be attached to a polypeptide to form a glycoprotein. [4]<ul><li>Glucose and galactose</li><li>Joined by condensation</li><li>Joined by glycosidic bonds</li><li>Added to polypeptide in golgi apparatus</li></ul> <div>Describe how the structure of starch is related to its function. [4] MS</div>1.      Helical/spiral shape so compact;<br>2.      Molecule is insoluble so osmotically inactive (does not affect<br>water potential)<br>3.      Branched so glucose is easily accessible by enzymes to break<br>down for respiration;<br>4.      Large molecule so cannot leave cell/cross cell-surface<br>membrane<br> Contrast the structure of a bacterial cell and the structure of a human cell. [7]<ul><li>Bacterial is much smaller than human</li><li>Bacterial has cell wall but human doesn't</li><li>Bacterial lacks nucleus but human has nucleus</li><li>Bacterial lacks membrane-bound organelles but human has membrane-bound organelles</li><li>Bacterial have 70S ribosomes whereas human have 80S ribosomes</li><li>Bacterial DNA is circular but human DNA is linear</li><li>Bacterial DNA is 'naked' whereas human DNA is bound to histones</li></ul> Explain why the diffusion of chloride ions involves a membrane protein and the diffusion of oxygen does not. [5]<ul><li>Chloride ions polar</li><li>Cannot cross lipid bilayer</li><li>Chloride ions transported by fd</li><li>Oxygen non-polar</li><li>Oxygen can diffuse across lipid bilayer</li></ul> Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells. [6] MS<ul><li>Cell homogenisation to break cells open</li><li>Filter to remove large debris</li><li>Use isotonic soltion to prevent damage to mitochondria</li><li>Keep cold to prevent damage by enzyme</li><li>Use buffer to prevent protein denaturation</li><li>Centrifuge at lower speed to separate nuclei</li><li>Re-spin supernatant at higher speed to get mitochondria in pellet at bottom</li></ul> Describe osmosis. [2]<ul><li>From a high water potential to a low water potential</li><li>Through aquaporins</li></ul> Describe facilitated diffusion. [2]<ul><li>Channel / carrier protein</li><li>Down concentration gradient</li></ul> Describe active transport. [3]<ul><li>Carrier protein</li><li>Against concentration gradient</li><li>Using ATP/energy from respiration</li></ul> Describe endocytosis. [1]Engulfing by csm to form vesicle Describe exocytosis. [1]Fusion of vesicle with csm Describe how a peptide bond is formed between two amino acids to form a dipeptide. [2]<ul><li>Condensation</li><li>Between amine and carboxyl group</li></ul> Describe how the secondary structure of a polypeptide is produced by bonds between amino acids. [2]<ul><li>Hydrogen bonds</li><li>Between NH and C=O</li></ul> Describe the function of DNA helicase.<ul><li>Unwinds DNA</li><li>Breaks hydrogen bonds between strands</li></ul> Describe the function of DNA polymerase.<ul><li>Joins nucleotides</li><li>Forms phosphodiester bonds</li></ul> Contrast the structures of ATP and a nucleotide found in DNA. [3]<ul><li>ATP has ribose whereas DNA nucleotide has deoxyribose</li><li>ATP has 3 Pi whereas DNA nucleotide has 1 Pi</li><li>ATP always has base adenine whereas base in DNA nucleotide can vary</li></ul> Describe <b>four</b> differences between the structure of a cellulose molecule and a glycogen molecule. [4]<ul><li>Alpha vs beta</li><li>branched vs straight cahin</li><li>Coiled vs straight chain</li><li>1,4 and 1,6 glycosidic bonds vs only 1,4 glycosidic bonds</li></ul> Describe the structure of glycogen. [3]<ul><li>Polysaccharide of alpha glucose</li><li>Joined by glycosidic bonds</li><li>Branched structure</li></ul> Suggest how glycogen acts as a source of energy. [2]<ul><li>Hydrolysed to glucose</li><li>Glucose used in respiration</li></ul> Compare and contrast the processes by which water and inorganic ions enter cells. [3]<ul><li>Both move down concentration gradient</li><li>Both move through protein channels in membrane</li><li>Ions can move against a concentration gradient by active transport</li></ul> <div>Give <b>two</b> ways in which the nucleotides in DNA are different from the nucleotides in RNA. [2]</div><ul><li>DNA contains thymine whereas RNA contains uracil</li><li>DNA contains deoxyribose whereas RNA contains ribose</li></ul> Draw the structure of ATP."<div style=""text-align: center;""><img src=""paste-abd2c1701b9dd837572c8ce809c88d1354890eae.jpg""></div>" <div>Explain how the organic bases help to stabilise the structure of DNA. [2]</div><ul><li>Hydrogen bonds between the base pairs holds two strands together</li><li>Many hydrogen bonds provide strength</li></ul> Describe how ATP is resynthesised in cells. [3]<ul><li>From ADP and Pi</li><li>By ATP synthase</li><li>During respiration/photosynthesis</li></ul> What are the main characteristics of benign tumors? [5]<ul><li>Grow slowly</li><li>Well differentiated</li><li>Normal, regular nuclei</li><li>Well defined borders (cells stick together to a particular tissue)</li><li>Easy to treat, can be normally removed by surgery</li></ul> What are the main characteristics of malignant tumors [5]<ul><li>Grow rapidly</li><li>Cells become unspecialised</li><li>Irregular, darker nuclei</li><li>Irregular / poorly defined borders</li><li>Removed by radiotherapy / chemo</li></ul> What is the normal function of a tumor suppressor gene? [3]<ul><li>Codes for proteins involved in control of cell division</li><li>Stopping the cell cycle</li><li>Involved in apoptosis of damaged/abnormal cells<br></li></ul> Describe 2 ways in which tumour suppressor genes can be affected that can lead to cancer [2]<ul><li>Mutation alters amino acid sequence and 3<sup>o</sup> structure of protein</li><li>Increased methylation prevents transcription</li></ul><div><br></div> What is the normal function of proto-oncogenes? [2]<ul><li>Code for proteins involved in control of cell division</li><li>Mainly stimulating cell division</li></ul> Describe ways proto-oncogenes can become involved in the development of tumors? [2]"<ul><li>Mutation could turn it into a permanently activated oncogene (causes uncontrolled cell division)</li><li>Decreased methylation / incr. acetylation causes <font color=""#ff0000"">excess transcription</font></li></ul>" What is the role of increased oestrogen concentration in the development of some breast cancers? How can this be minimised? [2]"- Increased conc. in areas such as adipose tissues in breasts causes uncontrolled cell division<div><br></div><div>Growth of cancer is minimised with drugs blocking the action of oestrogen in breasts</div><div><font color=""#ff0000"">(e.g Tamoxifen prevents oestrogen binding to OBP)</font></div>" What are benefits of genome sequencing becoming automated? [2]<ul><li>Cost effective </li><li>Can be done on a large scale</li></ul> Why is determining the genome of simpler organisms good for the development of vaccines? [2]<ul><li>Allows assignment of the proteins to each gene (easy because there's less non coding DNA)</li><li>This allows you to identify antigens on the surfaces of viruses / pathogenic bacteria</li></ul> Why can't the genome of a complex organism be easily translated into it's proteome? [2]<ul><li>Non coding DNA is present</li><li>Regulatory genes  are present</li></ul> How do prokaryotic cells differ from eukaryotic cells?<ul><li>cytoplasm lacks membrane-bound organelles</li><li>smaller ribosomes</li><li>no nucleus; instead they have a single, circular DNA molecule that is free in the cytoplasm and is not associated with protiens</li><li>a cell well that contains murein, a glycoprotein</li></ul><div>Many prokaryotic cells have:</div><div><ul><li>one or more plasmids</li><li>a capsule surrounding the cell</li><li>one or more flagella</li></ul></div> "Viruses are <span class=""cloze"" data-cloze=""acellular"" data-ordinal=""1"">[...]</span> and <span class=""cloze"" data-cloze=""non-living"" data-ordinal=""1"">[...]</span>. ""Viruses are <span class=""cloze"" data-ordinal=""1"">acellular</span> and <span class=""cloze"" data-ordinal=""1"">non-living</span>. <br> " What are the 3 statistical tests we use in Biology?<ul><li>student T-test</li><li>chi squared test</li><li>correlation co-efficient test</li></ul> What does standard deviation measure?the spread of the data around the mean  Describe how we use the P value in testing if results are significant"<ul> <li>The p value is the probability of results being due to chance</li> <li>Hence, if p<0.05 that means the results are <strong>significant</strong> <ul> <li>as there is less than a 5% chance that the results are due to chance</li> </ul> </li> <li>If p>0.05 that means the results aren't significant <ul> <li>as there is a greater than 5% chance that the results are due to chance</li> </ul> </li> <li><strong>We use 0.05 as we work at the 95% confidence interval.</strong></li></ul>" What is meant by degrees of freedom and how do we calculate this?"<ul> <li>The number of values that could vary</li> <li>How do we calculate degrees of freedom? <ul> <li>Usually equal to (n-1) where n = number of results</li> <li>If there are two sets of data, n1 + n2 -2 = degrees of freedom</li> </ul> </li></ul>" When do we use the student T-test?when comparing the mean values of two sets of data  Compare null hypothesis vs alternative hypothesis"<ul> <li>Null Hypothesis <ul> <li>There is <strong>not a significant difference</strong> between the two groups; any observed differences may be due to chance and sampling errors</li> </ul> </li> <li>Alternative Hypothesis (A2) <ul> <li>There is a significant difference between the two groups; the observed differences are most likely not due to chance or sampling error</li> </ul> </li></ul>" How do we use the null hypothesis in any statistical test?"<ul> <li>Assume it to be true</li> <li>Choose the correct statistical test</li> <li>Use this to generate a test statistic</li> <li>Compare this number against the critical value (unique for each test / depends on confidence level and degrees of freedom</li> <li>Can use this number to decide whether to accept or reject the null hypothesis</li></ul>" How can we use the T-test to compare two means?"<ul> <li>If the value for t is large, then there is a <strong>big difference in the mean</strong></li> <li>When the value for t <strong>exceeds the critical value</strong> (when P=0.05) then you can <strong>reject the null hypothesis</strong> as there is a significant difference.</li> <li>When saying where there is/isn't a significant difference, you must state also it in the context of the question</li></ul>" Describe the correlation coefficient test"<ul> <li>This test will allow us to calculate a <strong>correlation coefficient</strong> to identify whether there is a statistically significant correlation between</li> <li>If the value for r (calculated c.c) exceeds the critical value, then you can <strong>reject the null hypothesis</strong> because there is a strong enough correlation.</li></ul>" In a correlation coefficient test, what are the two possible results?"<ul> <li>Calculated value is greater than the critical value <ul> <li>There is less than a 5% probability that the correlation between variable 1 and variable 2 is due to chance</li> <li>Reject the null hypothesis</li> </ul> </li> <li>Calculated value is less than the critical value <ul> <li>More than 5% probability that correlation is due to chance</li> <li>Accept null hypothesis</li> </ul> </li></ul>" What is genetic diversity?The number of different alleles of genes in a population Give an example of directional selection and of stabilising selection<ul><li>stabilising - human birth weights</li><li>directional - antibiotic resistance</li></ul> "Eukaryotic DNA is <span class=""cloze"" data-cloze=""longer"" data-ordinal=""1"">[...]</span> than Prokaryotic DNA""Eukaryotic DNA is <span class=""cloze"" data-ordinal=""1"">longer</span> than Prokaryotic DNA<br> " "Murein is a <span class=""cloze"" data-cloze=""glycoprotein"" data-ordinal=""1"">[...]</span>""Murein is a <span class=""cloze"" data-ordinal=""1"">glycoprotein</span><br> " What are the two main stains we use during microscopy?<ul><li><b>Eosin </b>is used to highlight the cytoplasm</li><li><b>Iodine </b>contained in potassium iodide solution highlights starch grains</li></ul><br> Where does the energy in ATP come from?The unstable bonds between the phosphate molecules "Bacterial cells have <span class=""cloze"" data-cloze=""70S ribosomes"" data-ordinal=""1"">[...]</span> whereas human cells have <span class=""cloze"" data-cloze=""80S ribosomes"" data-ordinal=""1"">[...]</span>""Bacterial cells have <span class=""cloze"" data-ordinal=""1"">70S ribosomes</span> whereas human cells have <span class=""cloze"" data-ordinal=""1"">80S ribosomes</span><br> " What happens in cytokinesis?Cytoplasm divides to form 2 identical diploid daughter cells  Describe how comparisons of biological molecules in two species can be used to find out if they are closely related MS [8] <ul><li>Compare DNA</li><li>Sequence of bases / nucleotides;</li><li>Compare same protein</li><li>Sequence of amino acids</li><li><u>Immunological Evidence - no mark</u></li><li>Inject protein / serum into animal</li><li>Obtain antibodies</li><li>Add protein from other species</li><li>Amount of precipitate indicates relationship </li></ul> What occurs during an asthma attack? MS [4]<ul><li>smooth muscle in the bronchi contract</li><li>increased production of mucus by goblet cells</li><li>diameter of airways reduced</li><li>reduced flow of air</li></ul> Describe how a mutation can lead to a non-functional protein MS [4]<ul><li>Change in DNA base sequence</li><li>Change in amino acid sequence</li><li>Alters the position of hydrogen / ionic / disulfide bonds</li><li>Changes the tertiary structure of the protein</li></ul> Describe the role of micelles absorption of fats into the cells lining the ileum MS [5]<ul><li>Micelles include bile salts and fatty acids</li><li>Make the fatty acids more soluble in water</li><li>Bring/release/carry fatty acids to cell</li><li>Maintain higher concentration of fatty acids to cell </li><li>Fatty acids absorbed by diffufsion </li></ul> Alveolar epithelium cells, when they die, are replaced by thickened tissue. Explain why death of alveolar cells reduces gas exchange within tissues MS [3]1. Reduced surface area<div>2. Increased distance for <u>diffusion</u></div><div>3. Reduced <b>rate </b>of diffusion</div> Define introns and describe where they are positioned in the genome MS [2]<ul><li>DNA that does not code for amino acids</li><li>Positioned between genes </li></ul> What is a monoclonal antibody? MS [2] 1.Antibodies with the same tertiary structure<div>2. produced from identical plasma cells</div> State two ways in which monoclonal antibodies are used to treat disease MS [2]<ul><li>carries drug to specific antigens</li><li>blocks antigens/receptors </li></ul> Describe a method to quantify the amount of sugar in a solution <b>without a colorimeter</b> MS [3] <ul><li>Filter </li><li>Dry precipitate</li><li>Find mass / weight</li></ul> <div>State and describe the three main types of neurone</div><ul><li><strong>Sensory</strong> neurones carry impulses from <strong>receptors</strong> to the <strong>CNS</strong> (brain or spinal cord)</li><li><strong>Relay</strong> (intermediate) neurones are found entirely within the CNS and <strong>connect</strong> <strong>sensory</strong> and <strong>motor</strong> neurones</li><li><strong>Motor</strong> neurones carry impulses from the <strong>CNS</strong> to <strong>effectors</strong> (muscles or glands)</li></ul> Describe the structure of a Myelinated Motor Neurone [5]"<ul><li>long fibre known as an <b>axon</b></li><li>axon is insulated by a fatty sheath called <b>myelin sheath</b></li><li>small, uninsulated sections along its length called <b>Nodes of Ranvier</b></li><li>myelin is made by specialised cells known as <b>Schwann Cells; </b>these cells wrap themselves around the axon along its length</li><li><b>cell bodies </b>contain a <b>nucleus </b>and many extensions called dendrites</li></ul><div><br></div><div><img src=""A-neurone.png""><br></div>" What is meant by 'resting potential'?<div>In a resting axon, the inside of the axon always has a slightly negative electrical potential compared to outside the axon. </div> Define ecosystem"the community of biotic and abiotic factors of an area and their interactions. It is said to be <b>dynamic</b>" State 5 features of an ecosystem<ul><li>Dynamic</li><li>Can range in size from very small to very large</li><li>Can range in complexity (e.g a desert is relatively smple, a tropical rainforest is very complex)</li><li>Self-contained</li><li>Flow of energy and nutirents within it </li></ul> Why are ecosystems described as 'dynamic'?"<div>o   Populations constantly rise and fall<b></b></div> <div>o   Any small change can have a large effect<b></b></div> <div>o   Biotic and abiotic factors may alter the condition of the ecosystem<b></b></div>" What 4 factors affect population size and distribution?<ul><li>Interspecific Competition</li><li>Intraspecific Competition</li><li>Predation</li><li>Abiotic Factors </li></ul> What is interspecific competition?<div><br></div><div>What occurs when,</div><div><ul><li>two species are similarly well-adapted to the environment</li><li>one species is better adapted than the other</li></ul></div>"<ul><li>Competition for the <b>same resources </b>between individuals from different species</li></ul><div><br></div><div><b><u>Case 1 - Species are similarly well - adapted</u></b></div><div><ul><li>Both populations are limited, as each species has access to fewer resources and thus has less chance of survival and reproduction </li></ul><div><b><u>Case 2 - One species is better adapted than the other</u></b></div></div><div><ul><li>Leads to a decrease in population size of one of the species, and an increase in the population size of the other</li><li>This is because the latter species will out-compete the other for resources and thus has a greater chance of surviving and reproducing</li><li>An example is red vs grey squirrels, red squirrels can eat a wider range of food, are larger and store greater amount sof fat over the winter months, hence survive more often. </li></ul><div><br></div></div><div><img src=""Interspecific-competition-grey-and-red-squirrels.png""><br></div>" What is intraspecific competition? What is eventually reached as a result? Use grey squirrels as an example. "<ul><li>This is competition for the <strong>same resources</strong> between individuals from the <strong>same </strong>species</li><li>For example:</li><ul><li>When resources are plentiful, the population of grey squirrels increases</li><li>As the population increases, however, there are more individuals competing for these resources (e.g. food and shelter)</li><li>At some point, the resources become limiting and the population can no longer grow in size – the carrying capacity has been reached</li></ul></ul><div><br></div><div><img src=""Intraspecific-competition-grey-squirrels.png""><br></div>" Describe a predator-prey cycle in 3 steps"<ul><li><div>Prey is eaten by predator, resulting in predator population increasing and prey population decreasing<br></div></li><li><div><div>Fewer prey means increased competition for food, hence the predator population decreases<b></b></div></div></li><li><div><div>Fewer predators means more prey survives, cycle begins again <b></b></div></div></li></ul><img src=""7.4.3-Carrying-Capacity.png""><br>" What is meant by 'carrying capacity'?"The maximum stable population size of a species that an ecosystem can support<div><br></div><div><img src=""paste-736e56ecec4ff91de2fc6da1a39f4c8b002db6f2.jpg""><br></div>" Define the term 'niche'The role that an organism plays in a ecosystem, which is governed by adaptations to abiotic and biotic conditions  What is the competitive exclusion principle?<ul><li>A niche can only be occuped by one species, meaning that every individual species has its own unique niche</li><li><b>Competition for food / named resource;</b></li><li>If two species had identical nichces, one would go extinct</li><li>The better adapted outcompetes the other species</li></ul> What causes interspecific competition?Overlap between the niches of different species  Why is sampling carried out?To select a sample which is representative of the population What are the 5 key factors to consider when carrying out an ecological study?<ul><li>Large sample size</li><li>Removing bias</li><li>Seasonal differences</li><li>Choosing appropriate samples</li><li>Conclusions shown </li></ul> "Sampling can either be <span class=""cloze"" data-cloze=""random"" data-ordinal=""1"">[...]</span> or <span class=""cloze"" data-cloze=""systematic"" data-ordinal=""1"">[...]</span>""Sampling can either be <span class=""cloze"" data-ordinal=""1"">random</span> or <span class=""cloze"" data-ordinal=""1"">systematic</span><br> " Describe, in detail, how and why we use random sampling in an ecological study"<b><u>How:</u></b><div><ul><li>Two numbered axis are laid out over the sample area</li><li>RNG provides co-ordinates for area to study</li><li>With each area, every part has an equal chance of being chosen</li></ul><div><br></div></div><div><u style=""font-weight: bold;"">Why:</u><br><ul style=""""><li style="""">Eliminates bias</li></ul><div><br></div></div><div><br></div><div><img src=""paste-201aa24a1e43744953affac065a7315e2793eb76.jpg""><br></div>" How is systematic sampling different to random sampling?<ul><li>A similar grid is used, however samples are taken at regular intervals.</li><li>Usually used to investigate environmental gradient. </li></ul> How can we increase the reliability of data used in an ecological study? MS [6]<ul><li>Increase repeats</li><li>Calculate running mean</li><li>When enough quadrats used, graph would level off</li><li>Take enough readings to carry out statistical test</li><li>Test a large number to make sure results are reliable</li><li>Need to be sure work can be carried out in designated time</li></ul> Why do we use random samples? MS [3]<ul><li>Avoids bias</li><li>Data representative / Choice of X variable not influencing results</li><li>Allows use of statistical tests </li></ul> What are the 3 ways we can estimate population size?<div><br></div><div>When do we use each?</div><div><b><u>For non-motile and slow moving</u></b></div><ul><li>Quadrats (random)</li><li>Transects (systematic) </li></ul><div><br></div><div><b><u>For motile</u></b></div><ul><li>Mark, Release, Recapture</li></ul> What is meant by distribution of a species?describes how it is spread throughout the ecosystem What is meant by abundance?The number of individuals of that species Describe the two types of quadrats<ul><li>Frame Quadrats (place randomly, count number)</li><li>Point Quadrat (drop pins randomly, count number of species it touches)</li></ul> What are the 2 ways we can record data on species using quadrats?<ul><li>Percentage Cover</li><li>Species Frequency</li></ul> <br>What are the advantages/disadvantages of using Species Frequency when measuring with quadrats?"<div><span style=""color: rgb(0, 176, 80);"">Advantages:</span></div> <div>·         Quick to carry out</div> <div>·         Useful for species that are hard to count (e.g. grass)</div> <div><span style=""color: red;"">Disadvantages:</span></div> <div>·         Doesn’t provide detailed info on distribution of a species</div>" What are the advantages/disadvantages of using % cover when investigating with quadrats?"<div><span style=""color: rgb(0, 176, 80);"">Advantages:</span></div> <div>·         Useful for species that are hard to count (e.g. grass)</div> <div>·         Useful for species that are very abundant in area</div> <div>·         Don’t need to count individual plants</div> <div><span style=""color: red;"">Disadvantages:</span></div> <div>·         Not useful in areas where organisms occur in overlapping layers (becomes difficult to estimate an exact amount)</div>" Describe a method of random sampling via quadrats MS [3]<ul><li>Set up grid system with coordinates</li><li>Place <b>a large number of quadrats</b> at coordinates selected at <b>random</b></li><li>Count number of / estimate percentage cover of specise</li></ul> What are the 3 types of transect and how are they used?"<div><u><b>3 types </b><span style=""color: rgb(0, 176, 80);""></span></u></div><div><u><b><br></b></u></div><div><u><b><br></b></u></div> <div>o   <b>Line Transect</b></div> <div>§  Run a tape measure between two points</div> <div>§  Record all species that touch the tape</div><div><br></div><div>o   <b><span style=""color: rgb(0, 112, 192);"">Belt Transect</span></b></div> <div><span style=""color: rgb(0, 112, 192);"">§  </span><span style=""color: rgb(0, 112, 192);"">Use quadrats along the length of the transect</span></div><div><br></div><div>o   <b>Interrupted Transect</b></div> <div>§  Use quadrats at fixed intervals along the length of the transect</div>" "<div><b>‘’</b>Describe how you would investigate the distribution of x from one side of an ecosystem to the other’’ MS [3]</div>""<div>·         Transect from one side of the ecosystem to the other</div> <div>·         Place quadrats at regular intervals along the line</div> <div>·         Count the % cover of the plant in quadrats</div><div><br></div><div><br></div><div><img src=""paste-a1ea0c66295cb377a45f44cf6c5827369385bc60.jpg""><br></div>" Why are belt transects used in a non-uniform ecosystem?To investigate the effect of changing physical conditions on species distribution "<div>Why is more difficult to study animals and insects as opposed to plants?</div>""<div>·         Mobile</div> <div>·         Stay hidden from the investigator</div>" Describe the Mark-Capture-Rerelease Method [5]"<div>1.      Capture a known sample and mark them (without causing harm)</div> <div>2.      Release back into the community</div> <div>3.      Allow time for re-integration, the community is then revisited and a given number of individuals is caught again</div> <div>4.      The number of marked individuals is counted</div> <div>5.      Population size is calculated via the <span style=""color:red"">equation</span></div><div><span style=""color:red""><br></span></div><div><span style=""color:red""><br></span></div><div><img src=""paste-d226e4d8307ba413d63629bd55bf09573a04d9e1.jpg""><span style=""color:red""><br></span></div><div><span style=""color:red""><br></span></div>" What are the 4 issues surrounding the Mark-Capture-Rerelease method?"<div><div>·         Deciding in a large area how many individuals to capture and recapture</div> <div>·         Ensuring to mark them in a harmless way</div> <div>·         Ensure to mark in a way that stays til the second collection</div> <div>·         Deciding time for re-integration</div></div> " What are the assumptions we make when using the M.C.R method? MS  [6]<div><br></div><div><ul><li>No immigration / emigration</li><li>Few births / deaths (no losses to predation)</li><li>Proportion of marked / unmarked in both samples is the same as proportion in the habitat</li><li>Marked individuals evenly distribute themselves within the population</li><li>Markings aren't lost</li><li>Markings do not affect survival</li></ul></div> Define 'succession'The change over time in the species that occupy a particular area  Why would a bare, barren rock not be habituated by organisms?<ul><li>Exposed</li><li>No Soil</li><li>Absorbs + Reflects Heat</li><li>Dry</li><li>No Nutrients</li></ul> Describe the steps in primary succession. MS [6]"<ul><li>Colonisation occurs by a pioneer species</li><li>Pioneer species causes a change in environment e.g more food / nutrients / stabilises</li><li>Enables other species to colonise <b>once there is a change</b></li><li>Change (increase) in species diversity / biodiversity</li><li>Stability increases, environment is less hostile</li><li>Climax community is reached</li></ul><div><br></div><div><img src=""paste-a0852d6e32322ff19574d8c69b66d73f571370ae.jpg""><br></div>" What 5 things happen as a result of primary succession?<ul><li>Abiotic environment becomes less hostile</li><li>Greater number/variety of habitats and niches</li><li>Biodiversity increases</li><li>More complex food webs emerge</li><li>Increased biomass</li></ul> What is the role of pioneer species? MS [6]<ul><li>Stabilize environment</li><li>Soil development / increase humus</li><li>Change soil pH</li><li>Hold more water</li><li>Release more nutrients / increase N content</li><li>Provide shelter</li></ul> What is meant by 'climax community'?<ul><li>The final stage in succession</li><li>Community in equilibrium with environment</li><li>Community is stable</li></ul> What are the 3 key features of a climax community?<ul><li>Populations are stable around the carrying capacity</li><li>Abiotic factors constant</li><li>Same species present / stable community</li></ul> What are two types of succession and what's the difference?"<div><ul><li><b>Primary</b> succession occurs when plants grow in newly formed/exposed land and is gradually colonised.</li><li><b>Secondary</b> succession occurs when plants grow where there has previously been a population. These will have been destroyed e.g by fire</li></ul><div><br></div></div><div><br></div><div><img src=""paste-451f64583f3b3aa752c1ae6e9e03f8f95033ce72.jpg""><br></div><div><br></div><div><img src=""paste-ba72a212df1ab4b535c6f9ad1929bebfd506938d.jpg""><br></div> " Draw a table that summaries the differences between the two types of succession. [5]"<img src=""paste-685dd685751d63d22b28ff6bca96a066f2757d36.jpg"">" What do we need to know about animal succession?"<ul><li>Animal species present depend on the plant species found in the area</li><li><div>For example, mosses and grasses provide food and habitats for insects and worms. These can then support secondary consumers. </div></li></ul>" What is deflected succession?"<div>A community that remains stable on because human activity prevents succession from running its course</div>" Describe 5 ways in which deflected succession can be caused MS [5]<ul><li>Grazing</li><li>Burning</li><li>Mowing</li><li>Selective Herbicide</li><li>Exposure to Wind</li></ul> "<div>At each stage of succession, certain species may be recognized <span class=""cloze"" data-cloze=""which change the environment so that it becomes more suitable for
other species with different adaptations"" data-ordinal=""1"">[...]</span>. The new species may <span class=""cloze-inactive"" data-ordinal=""2"">change the environment in such a way that it becomes less suitable for the previous species</span></div>""<div>At each stage of succession, certain species may be recognized <span class=""cloze"" data-ordinal=""1"">which change the environment so that it becomes more suitable for other species with different adaptations</span>. The new species may <span class=""cloze-inactive"" data-ordinal=""2"">change the environment in such a way that it becomes less suitable for the previous species</span></div><br> " "<div>SL: Conservation of habitats frequently involves the <span class=""cloze"" data-cloze=""management of succession"" data-ordinal=""1"">[...]</span>. </div>""<div>SL: Conservation of habitats frequently involves the <span class=""cloze"" data-ordinal=""1"">management of succession</span>. </div><br> " Why may management of succession bring about benefits?"<div><ul><li>Maximising the growth of trees</li><li>Maximising the diversity of the habitat</li><li>Maximising the look of the countryside</li></ul></div> " Define 'conservation of habitats'The management of the natural resources to enable future generations to maximize their use  What does conservation of habitats involve?<ul><li>Maintaining ecosystems</li><li>Maininting biodiveristy</li><li>Management of existing resources</li><li>Ensuring damaged resources can be obtained again as well</li></ul> Describe how management of succession is used for Grouse<ul><li>Regular burning of grouse moors</li><li>Encourages new growth of heather shoots</li><li>Perfect habitat for grouse</li></ul> What are the 4 main reasons for conserving habitats?"<img src=""paste-8601402067408ea6943f82a8889445bcfed281b6.jpg""><div><ul><li>Economical - large genetical pool in organisms which coudl ead to the development of valuable resources in the future</li><li>Ethical - respecting living things that co-exist with us on Earth</li><li>Aesthetic Reasons</li><li>Cultural - people turn to nature for inspiration</li></ul></div>" "<div>Many species that previously existed on earth no longer do. Explain why in terms of succession and habitats.</div>""<div><ul><li>Habitats have changed or completely disappeared as a result of succession. </li><li>Some have been out competed by other species, mostly the dominant species in a community. </li></ul></div>" <div>How could we prevent species from dying out due to succession?</div>"<div><ul><li>Through the management of succession.</li><li>We can ensure that changes to habitats are minimal and that they only occur when needed.</li><li> Ensuring that any organisms displaced by change are placed into a suitable environment. <b> </b></li></ul></div> " Describe how the conservation of species can be achieved through managing succession"<div><ul><li>Climax communities do not contain all the species that existed in its earlier stages</li><li>Maintaining habitats at different stages of succession can <u>keep these species present</u>, by preventing change to the next stage                                            </li></ul></div> " An example of managing succession is Dormouse Conservation. Recall this.<ul><li>They feed on nuts + berries, found in coppiced forest lands such as hazel + oak</li><li>Numbers are in decline due to loss of habitat</li><li>Coppicing helps to maintain a stable environment</li><li>Halts the natural succession of scrubland + bramble into mature forest</li></ul> Grassland management is an example of conservation. Recall this.<ul><li>Much of the higher ground in the UK is moorland. </li><li>Vegetation growth rate slows significantly due to heather burning and sheep grazing</li><li>Burning maintains plant vigour and removes unwanted vegetation</li><li>Prevents climax community from being reached as the young tree saplings are destroyed => stopping progression into deciduous woodland</li></ul> What is sustainable foresty? Give two examples."<div>These are techniques that employ a variety of removal and replacement methods that provide timber while reducing the impact of timber removal on the environment.<b><u></u></b></div><div><br></div><div><br></div><div><b><u>Coppicing:</u></b></div><div><ul><li>Trees coppiced</li><li>Stems grow from stump</li><li>Stems provide wood from the stump</li></ul><div><b><u>Selection Logging</u></b></div></div><div><ul><li>Trees selected for removla based on height, girth</li><li>Felled individually and directed to fall to minimise damage</li><li>Forest managed to ensure continued growth of young seedlings + provide balance of tree ages</li></ul></div>" "<div>Describe how the percentage cover of heather plants on an area of moorland may be measured. MS [3]</div>""<div>1.     Use of quadrats; </div> <div>2.     randomly placed; </div> <div>3.     Estimate percentage of area shaded/covered by heather; </div>" How can microscopic plants lead to the development of an ecosystem? MS [13]"<div><div>1.     Pioneer species colonise area; </div> <div>2.     Microscopic plants at start</div> <div>3.     Can survive in hostile environment;</div> <div>4.     Death/decomposition</div> <div>5.     Change in abiotic conditions / <b>less hostile</b>/more stable / more habitats / niches; </div> <div>6.     By absorbing water / <b> adding humus</b></div> <div>7.     New species move into/colonise changed environment;</div> <div>8.     Increase in number / diversity of species / plants / animals;</div> <div>9.     New plants more successful than pioneer as can grow faster;</div> <div>10.   Conditions change to favour new species</div> <div>11.   New species outcompete old species; </div> <div>12.   So change in community over time, so increase in diversity;</div></div><div>13. Stability increases over time / less hostile enviromment leads to climax community</div><div><br></div>" When using M.C.R method of estimating population sizes, why may there be inaccuracies? MS [5]<ul><li>Sample too small</li><li>Too short a time to mix evenly;</li><li>Birth/death;</li><li>Immigration/emigration;</li><li>Marking method affected behaviour</li></ul> Given this data, describe the relationship between a predator and its prey. MS [6]"<div>1.     () year cycles;</div> <div>2.     predator peaks after prey;</div> <div>3.     prey increase due to low numbers of predators / available food;</div> <div>4.     more food for predators so numbers increase;</div> <div>5.     increased predation reduces number of prey;</div> <div>6.     number of predators decreases due to lack of food / starvation</div>" "<div>At each stage of succession, certain species may be recognized <span class=""cloze-inactive"" data-ordinal=""1"">which change the environment so that it becomes more suitable for other species with different adaptations</span>. The new species may <span class=""cloze"" data-cloze=""change the
environment in such a way that it becomes less suitable for the previous
species"" data-ordinal=""2"">[...]</span></div>""<div>At each stage of succession, certain species may be recognized <span class=""cloze-inactive"" data-ordinal=""1"">which change the environment so that it becomes more suitable for other species with different adaptations</span>. The new species may <span class=""cloze"" data-ordinal=""2"">change the environment in such a way that it becomes less suitable for the previous species</span></div><br> " How can smoking / air pollution lead to emphysema? [4]<ul><li>Due to smoking or air pollution exposure over large amounts of time<br></li><li>Particles are trapped in alveoli</li><li>Inflammation attracts phagocytes to the area</li><li>The phagocytes produce an enzyme that breaks down elastin in the alveoli walls</li></ul> Why can the mechanism that brings about characteristics be described as <b>enzymatic?</b><ul><li>All genes code for enzymes</li><li>Enzymes involved in biochemical pathway</li><li>Leads to characteristic in an organism </li></ul> Define 'genotype'The genetic constitution of an organism  What is a 'modification'?When the phenotype is NOT affected by the genotype, hence the characteristic hasn't been inherited.  What is a karyotype?An individuals collection of chromosomes Define 'dominant allele'Allele of the heterozygote that expresses itself in the phenotype  Define 'recessive allele'Allele of the heterozygote that is not expressed in the phenotype  If the allele on both loci = different, characteristic is...Heterozygous If allele on both loci = same, characteristic is...homozygous What is a monohybrid cross?<ul><li>Investigation into one characteristic</li><li>Shows what the offspring genotypes could be</li></ul> What is the name given to the respective generations of a Monohybrid Cross?<ul><li>First Gen = First Filial = F<sub>1</sub> </li><li>Second Gen = Second Filial = F<sub>2</sub> </li></ul> State the steps taken to draw a monohybrid cross to work out phenotypic ratio [5]<ul><li>Choose one letter to represent dominant / recessive</li><li>Work out the parental genotypes and gametes they might produce</li><li>Draw a Punnet Square</li><li>Look at phenotypes in F1 generation (write clearly)</li><li>Decide ratio of phenotypes </li></ul> What is meant by 'pure breeding'?Repeatedly breeding the dominant phenotype with other organisms of the dominant phenotype. This will create homozyogus dominant plants.  What is a dyhbrid cross?<ul><li>A cross involving two genes that control <b><u>two different characteristics</u></b></li><li>Unliked genes are found on <b>different chromosomes</b></li><li>Separated by random assortment during meiosis</li></ul> How could you determine if an organism with a dominant phenotype is heterozygous or homozygous?<ul><li>Cross organism with double recessive type</li><li>If homozygous -> all offspring will have dominant phenotype</li><li>If heterozygous -> at least one will have recessive phenotype </li></ul> What is the typical ratio expected in a dybrid cross if the two original parents were heterozygous?9:3:3:1 Define 'co-dominance'This is when both alleles are expressed in the phenotype How do we draw co-dominance crosses?"<ul><li>We no longer use Capital Letters since alleles are equally dominant</li><li>We instead choose a letter to represent the gene, and a superscripted letter to represent the allele</li></ul><div><img src=""paste-501cb0858d8b7b5c31801ac0d79c792befe4623d.jpg""><br></div>" Describe how Co-Dominance is demonstrated by Sickle-Cell Anameia<ul><li>Sickle Cell is caused by a gene that directions synthesis for haemoglobin</li><li>New protein causes a change in red blood cell, causing C shaped cell</li><li>Inhibits oxygen carrying capacity</li><li>Gene for Normal Hb = A</li><li>Gene for Sickle Hb = S</li><li>Genotype for Normal Cell: Hb<sup>A</sup>Hb<sup>A</sup></li><li>Genotype for Sickle Cell: Hb<sup>S</sup>Hb<sup>S</sup></li><li>A heterozygous mix, Hb<sup>A</sup>Hb<sup>S</sup> creates individuals with sickle cell trait. Express both types of cell. </li></ul> Why may be it advantageous for individuals to have sickle cell trait? (Hb<sup>A</sup>Hb<sup>S</sup>)<ul><li>Gives an individual resistance to malaria</li></ul> Explain how the inheritance of human blood groups is an example of 'multiple alleles'<ul><li>The gene has moer than 2 alleles</li><li>3 alleles associated with the 'I' gene</li><li>IA IB IO</li><li>Leads to diff. antigents being produced on membranes of RBCs</li></ul> State the various phenotypes and genotypes of human blood groups."<img src=""paste-d297b628c513c7c4f60b1eab04c5e4f9cb36f382.jpg"">" What antigens are produced by the multiple alleles for human blood type?"<ul><li>Allele IA leads to the production ofantigen A.</li><li>Allele IB leads to the production ofantigen B.</li><li>Allele IO leads to the production of <b>neither</b>.</li></ul><div><img src=""BloodTypes_ABO.png""><br></div>" How could you work out if somebody is I<sup>B</sup>I<sup>O</sup> and not I<sup>B</sup>I<sup>B</sup><ul><li>If one of their natural children is blood gorup O, both parents must've given IO</li><li>If their natural mother/father is blood group A, they must have passed on I<sup>O</sup>, otherwise the individual would be I<sup>A</sup>I<sup>B</sup></li></ul> What is meant by a 'dominance hierarchy'?<ul><li>If there are multiple alleles for a gene, more than 3, some alleles are <b>more dominant </b>to others</li></ul> "<div>No cloze 1 found on card. Please either add a cloze deletion, or use the Empty Cards tool.<br><a href='https://anki.tenderapp.com/kb/problems/no-cloze-found-on-card'>More information</a></div>""<div>No cloze 1 found on card. Please either add a cloze deletion, or use the Empty Cards tool.<br><a href='https://anki.tenderapp.com/kb/problems/no-cloze-found-on-card'>More information</a></div>" What is epistasis?When the allele of a gene affects or masks the expression of another in the phenotype  What are the two types of linkage in genetics?<ul><li>Sex linkage</li><li>Autosomal Linkage</li></ul> What is meant for genes to be linked? MS [1]"<div><div>1.     (Genes / loci) on same chromosome;</div></div>" <div>What is a sex linked gene? MS [1]</div>"<div>1.     Gene located on X/Y/ one sex chromosome </div>" "<div>Why can we use cats for experimentation? MS [3]</div>"<ul><li>Mammals, so similar physiological reactions as humans</li><li>Can use lots of thems</li><li>Small enough to keep in a lab </li></ul> <div>Why do small populations have lots of genetic disease? MS [5]</div>"<div>●      Small founder population/ common ancestor;</div> <div>●      Genetic isolation, small gene pool;</div> <div>●      Inbreeding;</div> <div>●      Reproduction occurs before symptoms apparent;</div> <div>●      So no selective disadvantage;</div>" What are the two divisions of the nervous system?<ul><li>Central Nervous System - (brain and spinal cord)</li><li>Peripheral Nervous System - (pairs of nerves that originate from either brain or spianl cord)</li></ul> What is ganglia?"<ul><li>structure containing many nerve cell bodies, typically linked by synapses.</li><li>well defined area of grey matter</li><li>present in spinal cord</li><li>relay neurone present within it</li></ul><div><img src=""Autonomic-ganglia-1024x576.jpg""><br></div>" Sensory, motor neurones and sense organs all belong to _____The peripheral nervous system  What is the Spinal Cord? [3]<ul><li>Column of nervous tissue</li><li>Runs along the back inside the vertebral column (for protection)</li><li>Emerging at intervals are pairs of nerves </li></ul> What is the difference between a somatic neuron and a visceral neuron?<ul><li>somatic = from/to the senses</li><li>visceral - from/to the organs </li></ul> What is a sense organ?A part of the body containing receptors  What is a stimulus?A detectable change in the internal/external environment  In the motor nervous sytem, what are the two divisions?<ul><li>Somatic (voluntary) nervous system - carries nerve impulses to body muscles</li><li>Autonomic (involuntary) nervous system - carries nerve impulses to glands / cardiac muscles / skeletal muscles </li></ul> Draw a flowchart from a stimulus being detected to a response."<img src=""Response-to-Change-Robin.png"">" The cell body of a neurone contains large amounts of RER, ribosomes and mitochondria. Explain why. MS [4]<ul><li>RER to package neurotransmitters</li><li>Ribosomes to synthesise neurotrasmitters/proteins involve</li><li>Proteins for the development of new neurones</li><li>Mitochondria for ATP involved in polypeptide synthesis </li></ul> What are the functions of Schwann Cells? [4]<ul><li>surrounds the axon for insulation</li><li>carries out phagocytosis</li><li>involved in nerve regeneration</li><li>wrap themselves around axon to build up myelin sheath</li></ul> Explain why reflex actions are so important MS [6]<ul><li>Automatic / involuntary adjustments to change in enviroment</li><li>Prevents injury </li><li>Role in homeostasis</li><li>Posture / Balance</li><li>Obtaining food / finding mate</li><li>Escape from predators </li></ul> State two features of simple reflexes<ul><li>Rapid</li><li>Do not have to be learnt</li></ul> What is a secondary nervous response?<ul><li>Relay neurone has synpase with OTHER relay neurones</li><li>Transmits impulses to sensory aeras</li><li>Allows a slower, secondary response in addition to the reflex</li><li>e.g saying ouch after you pick up a hot pan</li></ul> Give ways in which hormonal coordination differs from nervous coordination MS [5]<ul><li>chemical (not electrical)</li><li>slower (to take effect / transmission)</li><li>longer-lasting</li><li>delivered by blood (not nerves)</li><li>broader targetting</li></ul> Define 'nerve impulse'self-propagating wave of electrical activity that travels down the axon membrane Explain why energy is required in the maintenance of the resting potential in an axon. [2] MSATP / energy required by ion pumps<br><br>To move Na+ and K+ against concentration gradient Sodium and potassium ions can only cross the axon membrane through proteins. Explain<br>why. [2] MScan not pass through phospholipid bilayer;<br><br>because water soluble / not lipid soluble / charged / hydrophilic / hydrated; Proteins A and B differ from each other. Explain why different<br>proteins are required for the diffusion of different ions through the<br>membrane. MS [2]<ul><li>each protein has specific tertiary structure</li><li>because ions have different sizes and shapes </li></ul> Describe a simple reflex arc MS [3]<ul><li>receptor to sensory, relay, moton neuron to effector (two synapses)</li><li>only to spinal cord, no brain, hence no thinking</li><li>fast and involuntary, prevents injury, escape from predators</li></ul> Recall the stages by which an action potential is generated1. Stimulus<div>2. Depolarisation</div><div>3. Repolarisation</div><div>4. Hyperpolarisation</div><div>5. Refractory Period</div> Generation of AP: Stimulus<ul><li>Neurone CSM excited</li><li>Na+ V.G channels open</li><li>CSM more permeable to Na+</li><li>Na+ diffuse down <b>e.c gradient</b> into neurone</li><li>Inside of neurones become less -ve</li></ul> Generation of AP: Depolarisation<ul><li>Threshold reached</li><li>Many more Na+ channels open</li><li>More Sodium Ions diffuse in (+ve feedback)</li><li>Potenetial rises rapidly </li><li>P.D peaks around +40mV</li></ul> Generation of AP: Repolarisation<ul><li>At 40mV</li><li>Na+ V.G channels <b><u>close</u></b></li><li>All K+ V.G channels <b><u>open</u></b></li><li>K+ diffuse down conc. gradient <b>out </b>of the axon</li><li>Inside of membrane becomes more negative again</li></ul> Generation of AP: Hyperpolarisation<ul><li>K+ ions channels slow to close</li><li>Overshoot of K+</li><li>Too many diffuse out</li><li>P.D becomes <b>more -ve </b>than R.P</li></ul> Generation of AP: Refractory Period<ul><li>Ion channels reset</li><li>NaK pump returns membrane to R.P</li><li>Another AP cannot be generated in this time</li></ul> What is the importance of the refractory period? 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} if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> "" <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""cbb394fa3d364a80ae0e79d7dd9ec29d-ao-8-A.svg"" /></div> <div id=""io-original""><img src=""215-action-potential-voltage-time-graph.png"" /></div> </div> <button id=""io-revl-btn"" onclick=""toggle();"">Toggle Masks</button> <div id=""io-extra-wrapper""> <div id=""io-extra""> </div> </div> <script> // Toggle answer mask on clicking the image var toggle = function() { var amask = document.getElementById('io-overlay'); if (amask.style.display === 'block' || amask.style.display === '') amask.style.display = 'none'; else amask.style.display = 'block' } // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> " What is the 'all or nothing' principle? [3]<ul><li>AP only occurs when membrane is depolarised to a certain threshold (-55mV)</li><li>If this is not reached, AP will not be triggered</li><li>A bigger stimulus won't cause a bigger AP, AP is just fired more frequently </li></ul> "<div>A myelinated axon conducts impulses faster than a non-myelinated axon. Explain this difference. MS [3]</div>""<div>1.     (In myelinated) action potential / depolarisation only at node(s) of Ranvier; </div> <div>2.     (In myelinated, nerve impulse) jumps from node to node / saltatory; </div> <div>3.     (In myelinated) action potential / impulse does not travel along whole length; </div>" <div>How can axons conduct faster? MS [7]</div>"<div>1.     Myelinated;</div> <div>2.     So saltatory conduction;</div> <div>3.     Larger diameter;</div> <div>4.     So less resistance to flow of ions; </div><div>5.     Higher temperature (up to 40<sup>o</sup>C);</div><div>6.      Ions diffuse faster since more Ke; </div><div>7.      Faster r8 of respiration, more ATP for ATrans</div>" What the consequences of a myelin sheath being broken down?<ul><li>Less/no saltatory conduction</li><li>More depolarisation over length of membranes </li><li>Slower impulse transmission</li></ul> How is an AP propagated along an unmyelinated neurone? (in terms of region A and B, adjacent parts of a neurone)<ul><li>Influx of Na+ in region A</li><li>Localised current</li><li>Result in Na+ V.G.C opening in region B</li><li>Na+ diffuse into region B</li><li>K+ ion channels open in Region A (repolarisation)</li></ul> "In a myelinated neurone, <span class=""cloze"" data-cloze=""nerve impulses jump from node to node"" data-ordinal=""1"">[...]</span>. This is called <span class=""cloze-inactive"" data-ordinal=""2"">saltatory conduction</span>. ""In a myelinated neurone, <span class=""cloze"" data-ordinal=""1"">nerve impulses jump from node to node</span>. This is called <span class=""cloze-inactive"" data-ordinal=""2"">saltatory conduction</span>. <br> " "In a myelinated neurone, <span class=""cloze-inactive"" data-ordinal=""1"">nerve impulses jump from node to node</span>. This is called <span class=""cloze"" data-cloze=""saltatory conduction"" data-ordinal=""2"">[...]</span>. ""In a myelinated neurone, <span class=""cloze-inactive"" data-ordinal=""1"">nerve impulses jump from node to node</span>. This is called <span class=""cloze"" data-ordinal=""2"">saltatory conduction</span>. <br> " Two properties of myelin? [2]<ul><li>Lipid</li><li>Electrical Insulator</li></ul> What do we mean when we say a neurone membrane is polarised / depolarised?<ul><li>Polarised = more -ve on inside</li><li>Depolariesd = more +ve on inside</li></ul> Why are males more likely to develop a sex-linked disorder?<ul><li>X longer than Y</li><li>No homologous Y area for most of X</li><li>Hence males only require 1 copy of a recessive allele for expression on the phenotype </li></ul> What is Haemophilia?<ul><li>Sex-linked disease</li><li>Blood clots slowly as clotting factors aren't coded for</li></ul> Why do males always inherit a sex-linked condition from their mother?<ul><li>Males are XY</li><li>They inherit X chromosome from their mother </li></ul> How do you interpret pedigree charts?<ul><li>▢ = male<br></li><li>O = female</li><li>shading = sufferer</li><li>dot = carrier</li></ul> How can you identify, from a pedigree chart, that a disease is recessive?<ul><li>Unaffected parents givinsg rise to affected individual</li><li>Parents are heterozygous</li><li>Only possible with recessive</li></ul> <br>How can you identify that a disease is sex-linked from a pedigree chart?<ul><li>Only/primarily males in pedigree affected</li><li>Generations are skipped </li></ul> What is autosomal linkage?"<ul><li>Autosome = non-sex chromosome</li><li>Genes present on same autosome</li><li>Inherited together</li></ul><div><br></div><div><img src=""paste-53b0e318f366f0ceebdc042aba6c526f9e22ec7c.jpg""><br></div>" X and Y chromosomes do not form a typical bivalent during meiosis. Explain why MS [2]<ul><li>X and Y chromosomes different sizes / shapes</li><li>Most of length not homologous / unable to line up</li></ul> "The closer the loci of genes on an autosome, <span class=""cloze"" data-cloze=""the more closely linked they are"" data-ordinal=""1"">[...]</span> because <span class=""cloze"" data-cloze=""they are less likely to be separated during crossing over"" data-ordinal=""1"">[...]</span>""The closer the loci of genes on an autosome, <span class=""cloze"" data-ordinal=""1"">the more closely linked they are</span> because <span class=""cloze"" data-ordinal=""1"">they are less likely to be separated during crossing over</span><br> " In autosomal linkage, how do the genotypes of the offspring compare to the parents? When may this not be the case?<ul><li>Most offspring will have the same genotype and phenotype as parents</li><li>Unless alleles are separated during crossing over</li></ul> Define 'gene pool'All the alleles of all genes in a population Define 'allele frequency'The number of times an allele occurs within a gene pool What are the 5 assumptions for the Hardy-Weinberg equations?<ul><li>No mutations or selection</li><li>Isolated and large population</li><li>Random mating<br></li></ul> What is the Hardy-Weinberg equations and how do we use these in calculations?"<ul><li>If the phenotype of a trait in a population is determined by a single gene with only two alleles (we will use <strong>B / b </strong>as examples throughout this section<strong>)</strong>, then the population will consist of individuals with three possible genotypes:<ul><li><strong>Homozygous</strong> dominant <strong>(BB)</strong></li><li><strong>Heterozygous (Bb)</strong></li><li>Homozygous recessive (<strong>bb)</strong></li></ul></li><li>When using the Hardy-Weinberg equations the <strong>frequency of a genotype</strong> is represented as a <strong>proportion</strong> of the population<ul><li>For example, the <strong>BB</strong> genotype could be 0.40</li><li>Whole population = 1</li></ul></li><li>The letter <strong><em>p</em></strong> represents the frequency of the dominant allele (<strong>B)</strong></li><li>The letter <strong><em>q</em></strong> represents the frequency of the recessive allele (<strong>b)</strong></li><li>As there are only two alleles at a single gene locus for this phenotypic trait in the population:</li></ul><div style=""text-align: center;""><strong><em>p + q</em> = 1</strong></div><ul><li><div style=""text-align: left;"">The chance of an individual being homozygous dominant is <strong><em>p</em><sup>2</sup></strong></div><ul><li>In this instance, the offspring would inherit dominant alleles from both parents ( <strong><em>p </em></strong>x<strong><em> p </em></strong>=<strong><em> p</em></strong><sup>2</sup><em> )</em></li></ul></li><li>The chance of an individual being heterozygous is <strong>2<em>pq</em></strong><ul><li>Offspring could inherit a dominant allele from the father and a recessive allele from the mother (<strong><em> p</em></strong> x <strong><em>q</em></strong> ) <strong>or </strong>offspring could inherit a dominant allele from the mother and a recessive allele from the father (<strong><em> p</em></strong> x <strong><em>q</em></strong> ) = 2<strong><em>pq</em></strong></li></ul></li><li>The chance of an individual being homozygous recessive is<strong> <em>q</em><sup>2</sup></strong><ul><li>In this instance, the offspring would inherit recessive alleles from both parents ( <strong><em>q </em></strong>x<em><strong> q</strong> </em>=<strong><em> q</em></strong><sup>2</sup><em> )</em></li></ul></li><li>As these are all the possible genotypes of individuals in the population the following equation can be constructed:</li></ul><div style=""text-align: center;""><strong><em>p</em><sup>2</sup> + <em>q</em><sup>2</sup> + 2<em>pq</em> = 1</strong></div>" What is the Hardy-Weinberg <b>principle</b>? (not the equations)<div>There is an equilibrium between allele frequencies, and there is no change in this between generations. </div> Describe how to set up a Potometer accurately MS [8] 1. Seal joints / ensure airtight / ensure watertight; <div>2. Cut shoot under water; </div><div>3. Cut shoot at a slant; </div><div>4. Dry off leaves; </div><div>5. Insert into apparatus under water;</div><div> 6. Ensure no air bubbles are present;</div><div> 7. Shut tap; </div><div>8. Note where bubble is at start / move bubble to the start positio</div> Why would increasing the temperature above 40 degrees decrease the rate of propagation of an electrical impulse?Proteins Denature Describe the processes that occur at a cholinergic synapse. MS [8]1. (impulse causes) calcium ions / Ca++ to enter axon;<br>2. vesicles move to / fuse with (presynaptic) membrane;<br>3. acetylcholine (released);<br>4. (acetylcholine) diffuses across synaptic cleft / synapse;<br>5. binds with receptors on (postsynaptic) membrane;<br>6. sodium ions / Na+ enter (postsynaptic) neurone;<br>7. depolarisation of (postsynaptic) membrane;<br>8. if above threshold nerve impulse / action potential produced What happens to acetylcholine after it has triggered an AP in the post-synaptic membrane? [3] <ul><li>Acetylcholinesterase breaks down acetylcholine in the cleft (into acetate + choline)</li><li>These diffuse back into pre-synaptic membrane<br></li><li>ATP resynthesises + stores back into vesicles (assisted by SER) </li></ul> What are the 5 types of drugs that affect synaptic transmission?<ul><li><b>Agonist</b>; binds to receptor, produces functional response</li><li><b>Antagonist</b>; prevents agonist from binding to receptor</li><li><b>Enzyme </b>Inhibition; inhibits enzymes that break down NT</li><li><b>Stimulating </b>NT; more receptors activated<br></li><li><b>Inhibiting </b>NT; less receptors activated</li></ul> What criteria must be met in order for chi-squared to be used? [4]<ul><li>relative large sample</li><li>data in discrete catagories</li><li>raw values must be used</li><li>must be investigating observed vs expected</li></ul> In a chi squared test, what are the 2 possible outcomes?<b>1. calculated > critical</b><div><br></div><div>We reject the null hypothesis. There is less than a 5% probability that the difference between the observed and expected frequencies is due to chance and so the difference is significant.</div><div><br></div><div><br></div><div><br></div><div><b>2. critical > calculated</b></div><div><br></div><div>We accept the null hypothesis. There is more than a 5% probability that the difference between the observed and expected frequencies is due to chance and the so the difference is not significant. </div> "Species exist as <span class=""cloze"" data-cloze=""one or more populations"" data-ordinal=""1"">[...]</span>""Species exist as <span class=""cloze"" data-ordinal=""1"">one or more populations</span><br> " Explain the processes by which stabilising selection occurs MS [6]<ul><li>Unchanging conditions of environment</li><li>Variation between individuals due to mutation</li><li>Extreme phenotypes selected against / less likely to survive + reproduce</li><li>Small variation in allele frequency</li><li><u>Mean </u>value is unaltered / <u>range </u>is reduced</li><li>Repeats over many generations</li><li>Increasing proportion of populations become well adapted to the environment</li></ul> Why may there be a time lag between the prevalence of an allele and the introduction of a selection pressure? MS [3]<ul><li>Initially, only some individuals have a favourable mutation</li><li>Differential reproductive success; Individuals with favourable allele will have offspring</li><li>Takes many generations for mutation to become the most common allele</li></ul> What are the 3 sources of genetic variation?<ul><li>Mutation (primary source)</li><li>Meiosis</li><li>Random fertilisation</li></ul> Why do individuals within a population show a wide range of variation in phenotype? [2]<ul><li>Genetic factors</li><li>Environmental factors </li></ul> Give 3 examples of selection pressure during natural selection.<ul><li>Predation</li><li>Disease</li><li>Competition</li></ul> What is the effect of differential reproductive success on allele frequencies?Frequency of <u>favourable </u>alleles increases<br> Explain how allopatric speciation occurs MS [6]<ul><li>Geographical isolation</li><li>Separate genes pools / no interbreeding or gene flow</li><li>Variation due to mutation</li><li>Different selection pressures / habitats</li><li>Differential reproductive success </li><li>Leads to a change in allele frequency</li></ul> Explain how sympatric speciation occurs MS [6]<ul><li>Occurs in the same habitat</li><li>Mutation causes variation (link to specific phenotype)</li><li>Reproductive isolation</li><li>Different alleles passed on</li><li>Disruptive selection occurs</li><li>Eventually different species formed - cannot interbreed to produce fertile offspring</li></ul> SL: What does reproductive separation of two populations lead to? [3] <ul><li>Accumulation of genetic differences</li><li>Leads to an inability of members of the populations to interbreed and produce fertile offspring</li><li>New species arise - sympatric speciation </li></ul> Describe the concept of genetic drift. [3]<div><ul><li>Random changes in alele frequency in a gene pool</li><li>Effect is much more drastic in small populations</li><li>Driven forward by chance, not selection</li></ul></div> What are the two types of genetic drift?"<ul><li>Founder Effect</li><li>Bottleneck Effect</li></ul><div><br></div><div><br></div><div><img src=""paste-6715001c9c2fbf0fc9a3c5924a0ec327e996d0f8.jpg""><br></div>" What is the founder effect? [3]<div><br></div><div>Give 2 examples. </div><ul><li>small group of individuals break off to form a smaller colony</li><li>founding individuals may not represent the full genetic diversity</li><li>evolve in different direction if they are subjected to <b>diff. selection pressures </b>and if the population is <b>missing alleles </b></li></ul><div><br></div><div>EXAMPLES:</div><div><ul><li>Blue Fugates (blue skin)</li><li>The Amish People (recessive conditions)</li></ul></div> What is a genetic bottleneck? [4] <div><br></div><div>Give two examples. </div><ul><li>A sharp reduction in the size of a population</li><li>Produce smaller pop. with reduced genetic diversity.</li><li>In subsequent generations, diversity remains lower.</li><li>Slowly increases with time thanks to random mutations. </li></ul><div>EXAMPLES:</div><div>1. Environmental events (floods, fires)</div><div>2. Human activities (hunting, habitat destruction)</div> Describe what occurs in the light-independent reaction / Calvin Cycle. MS [7]"1. Carbon dioxide combines with ribulose bisphosphate / RuBP; <font color=""#ff0000"">5C + 1C</font><br>2. Produces two glycerate (3-)phosphate / GP; <font color=""#ff0000"">2 x 3C</font><br>3. GP reduced to triose phosphate / TP; <font color=""#ff0000"">2 x 3C</font><br>4. Using reduced NADP; (provides H)<br>5. Using energy from ATP;<br>6. Some triose phosphate converted to glucose / hexose / other useful organic substnaces<div>7. Some triose phosphate is used to generate RuBP in the Calvin Cycle</div>" Describe what occurs during the light-dependent reaction MS [7]1. Chlorophyll absorbs light energy;<br>2. Excites electrons / electrons removed (from chlorophyll);<br>3. Electrons move along carriers / electron transport chain releasing energy;<div><br><div><i>3b. Energy used to pump H+ across thylakoid membrane; H+ diffuses out through ATP synthase, providing energy for ATP synthesis</i></div><div><i><br></i>4. Energy used to join ADP and Pi to form ATP;<br>5. Photolysis of water produces protons, electrons and oxygen;<br>6. NADP reduced by electrons / electrons and protons / hydrogen;</div></div> What enzyme catalyses the reaction of RuBP to form 2GP?Rubisco What does the Pacinian corpuscle illustrate? [2] <ul><li>receptors respond only to <b>specific stimuli</b></li><li>stimulation of a receptor leads to establishment of a GP </li></ul> Explain how applying pressure ot the Pacinian Corpuscle leads to the generation of an AP. [5]"<ul><li>Pressure causes membrane / lamellae to become <font color=""#ff0000"">distorted </font>/ stretched;</li><li><font color=""#ff0000"">Stretched-mediated</font> Na+ ion channels open</li><li>Na+ ions diffuse into the neurone; <font color=""#ff0000"">depolarising </font>the membrane and producing a GP</li><li>Greater pressure causes <font color=""#ff0000"">more </font>channels to open / more Na+ to enter <br></li><li>GP creates AP if <font color=""#ff0000"">threshold </font>reached</li><br></ul>" Where are Pacinian Corpuscles present? [2]<ul><li>abundant deep in the skin</li><li>occur in joints, ligaments and tendons i.e fingers, feet soles, external genatalia </li></ul> Sketch and label the structure of the Pacinian Corpuscle: "<img src=""Structure-of-Pacinian-corpuscle.png"">" Draw a diagram to <b>contrast </b>the differences in neural pathways of rod and cone cells. "<img src=""Connection-of-rods-and-cones.png"">" The heart controls and coordinates the regular contraction of the atria and the ventricles. Describe how. MS [7] "1. SAN initiates heartbeat / acts as a pacemaker / myogenic;<br>2. SAN sends wave of electrical activity across atria causing atrial<br>contraction;<div>3. Non-conducting tissue prevents immediate contraction of ventricles / prevents<br>impulses reaching the ventricles;<br>4. AVN delays (electrical activity / impulses);<br>5. (Allowing) atria to empty before ventricles contract / ventricles to fill before they<br>contract;<br>6. (AVN) sends wave of electrical activity / impulses down Bundle of His / Purkyne<br>fibres;<br>7. Causes ventricles to contract from base up / ventricular systole;</div><div><img src=""a3gkASD.gif""><br></div>" What does SAN stand for?sinoatrial node What does AVN stand for?atrioventricular node What are the two branches of the autonomic nervous system and their functions?1. Parasympathetic; inhibits effectors<div>2. Sympathetic; stimulates effectors</div> What are the carotid arteries?arteries that serve the brain Explain how chemoreceptors respond to a low pH / high CO<sub>2</sub> blood conc. [5]"1. Chemoreceptors (in carotid arteries / aorta) detect rise in CO<sub>2</sub> / acidity / fall in pH<div>2. Increases frequency of impulses to cardiac centre / medulla oblongata</div><div>3. Increases frequency of impulses to the SAN via the <font color=""#ff0000"">sympathetic nervous system</font></div><div>4. <font color=""#ff0000"">Noradrenaline </font>is secreted at synapse between sympathetic neurone + SAN; (stimulates SAN)</div><div>5. Increases rate of electrical wave production by the SAN; increases heart rate</div>" Explain how chemoreceptors detect a rise in blood pH / low CO<sub>2</sub> blood conc. [5]"1. Chemoreceptors (in carotid arteries / aorta) detect fall in CO<sub>2</sub> / rise in pH<div>2. Increases frequency of impulses to cardiac centre / medulla oblongata</div><div>3. Increases frequency of impulses to the SAN via the <font color=""#ff0000"">parasympathetic nervous system</font></div><div>4. <font color=""#ff0000"">Acetylcholine </font>is secreted at synapse between parasympathetic neurone + SAN; (stimulates SAN)</div><div>5. Decreased rate of electrical wave by the SAN; lowers heart rate</div>" How does an increased heart rate lead to a decrease in the blood conc. of CO<sub>2</sub> ?<ul><li>Increased blood flow</li><li>More CO<sub>2</sub> removed by the lungs</li><li>Conc. returns to normal </li></ul> Explain how baroreceptors detect and respond to a rise in blood pressure. [5] "1. Baroreceptors detect rise in blood pressure<div>2. Increases the frequency of impulses to the cardiac centre / medulla</div><div>3. Increases the frequency of impulses to the SAN via the <font color=""#ff0000"">parasympathetic </font>nervous system </div><div>4. Acetylcholine is released at the synapse between the para neurone and the SAN</div><div>5. <font color=""#ff0000"">Decreases </font>the rate of production of electrical waves by the SAN; therefore decreases heart rate </div>" Explain how baroreceptors detect and respond to a fall in blood pressure. [5] "1. Baroreceptors detect fall in blood pressure<div>2. Increases the frequency of impulses to the cardiac centre / medulla</div><div>3. Increases the frequency of impulses to the SAN via the <font color=""#ff0000"">sympathetic </font>nervous system </div><div>4. Noradrenaline is released at the synapse between the sympathetic neurone and the SAN</div><div>5. <font color=""#ff0000"">Increases </font>rate of production of electrical waves by the SAN; therefore increases heart rate </div>" Define 'limiting factor'.At any given moment, rate of a physiological process is limited by the factor that is at its least favourable vlaue. What are the 5 key limiting factors of photosynthesis?1. Light intensity<div>2. Temperature</div><div>3. Avaliability of water</div><div>4. Avaliability of chlorophyll</div><div>5. Avaliability of CO<sub>2</sub></div> What is meant by 'compensation point'?<ul><li>No net exchange of gases</li><li>Rate of photosynthesis is equal to the rate of respiration </li></ul> How does the effect of <b>temperature </b>provide evidence for the light independent reaction?<ul><li>A purely photochemical reaction won't be affected by temperature</li><li>Photosynthesis <b>is </b>affected by temperature; its not a purely light based reaction</li></ul> What is the percentage of CO<sub>2</sub> in the atmosphere?0.04% What is the optimum concentration of CO<sub>2</sub> required for photosynthesis?0.1% T/F: Plants do not respire during the day. Explain your answer. <ul><li>FALSE.</li><li>Plants respire ALL the time; to produce ATP. </li><li>Respiration is often masked by photosynthesis; which produces oxygen faster than respiration takes it up. Hence, the effects of respiration aren't always apparent until night when photosynthesis stops. </li></ul> Why do photosynthesis and respiration have different <b>optimum </b>temperatures?<ul><li>Catalysed by <b>different enzymes</b><br></li><li>Different <b>optimums</b></li></ul> Explain why the rate of the LIR decreases at low temperatures. MS [3] <ul><li>Enzymes involved</li><li>Slower rate of enzyme at lower temperatures</li><li>Less kinetic energy / fewer collisions</li></ul> Why are glasshouses used in agriculture? [3]<ul><li>Better yield</li><li>Crops can be grown out of season</li><li>Grow plants in regions they would not occur naturally </li></ul> How are glasshouses used in agriculture?Optimum conditions for plant growth are maintained<br><div><ul><li>Optimum temperature</li><li>Water loss controlled</li><li>Humidity monitored</li><li>Specific wavelengths of light used </li></ul><div>With these limiting factors controlled, higher levels of photosynthesis means more carbs are produced. Produce energy for faster growth and fruit formation. </div></div> Explain how light intensity / <b>wavelength </b>affects the rate of photosynthesis. [4]<b>INTENSITY:</b><div><ul><li>More energy for photoionisation in the L.D.R; hence faster rate of photosynthesis</li><li>If low, LDR is slower. ATP and NADPH not produced, hence conversion of GP into TP will be slower. GP will rise (still being made) and TP + RUBP will fall (used to make GP) </li></ul><div><b>WAVELENGTH:</b></div><ul><li>Light needs to be at a particular <b>wavelength </b>(leaves look green because they reflect green light - they absorb blue + red)</li><li><b>Different pigments absorb </b><b>different wavelengths </b></li></ul></div> Explain how temperature affects the rate of photosynthesis. [3]<ul><li>Calvin Cycle is controlled by enzymes (e.g rubisco)</li><li>At low temperatures, slower reactions as enzyme works more slowly</li><li><b>Levels of RuBP, GP and TP will fall </b></li><li>Increasing temp. increases rate up to optimum; beyond optimum, rate decreases.</li><li>High temp can cause stomata to close (stress response): less CO<sub>2, </sub>less Calvin Cycle</li></ul> Why is photosynthesis slow in green light? MS [3]<ul><li>Less absorption of light / more reflection of (green) light;</li><li>Due to the green colour of chlorophyll;</li><li>Light required for light dependent reaction / photolysis;</li></ul> Why is it important for plants to produce ATP in respiration as well as photosynthesis? MS [6]<ul><li>ATP required for ATrans</li><li>ATP required for synthesis of macromolecules</li><li>Plants use more ATP than produced in photosynthesis</li><li>No ATP production in the dark</li><li>Some tissues unable to photosynthesise</li><li>ATP cannot be moved from cell to cell</li></ul> "<div>How do rod cells enable us to see in conditions of low light intensity? MS [4]</div>""<div>1.     Several rod cells to each neuron/convergence;</div> <div>2.     Principle of additive effect of light striking several rod cells/(<b>spatial</b>) summation; </div> <div>3.     Exceeds threshold;</div> <div>4.     Individual generator potentials do not exceed threshold;</div>" <div>How does spatial summation work? MS [3]</div><ul><li>Impulses from two neurones;</li><li>Causes sufficient depolarisation</li><li>To reach threshold</li></ul> How do cone cells enable us to distinguish between objects close together? MS [2]<ul><li>Each cone connected to a single neuron;</li><li>Brain receives information from each cone individually</li></ul> Why is dry mass an approximate measure? MS [2]"<div>●      Dry mass measures / determines increase in biological / organic material;<br></div> <div>●      Water content varies;</div>" How do you measure dry mass? MS [2] <div>●      Record mass and reheat</div><div>●      Until constant mass recorded</div> What factors must be considered when evaluating a study? [10]<ul><li>Number of times the study was carried out - sufficient times?</li><li>Sample size - too big/small</li><li>Control experiment - done/not done</li><li>Period of time - long/short</li><li>Carried out in animals/culture - representative of humans?</li><li>Shown as % changes - comparable if so</li><li>Sampling bias - chosen randomly?</li><li>Double blind test / placebo</li><li>Statistical test - results may not be significant</li><li>Patients lying - over/under exaggerate</li></ul> In general, what variables must be controlled in a <b>human </b>study?<ul><li>Age</li><li>Lifestyle</li><li>Ethinicity</li><li>Exercies</li><li>Smoking</li><li>Diet</li><li>Weight</li><li>Medical History</li></ul> In general, what variables must be controlled in a <b>plant </b>study?<ul><li>Species</li><li>Height</li><li>Number of leaves</li><li>Number of stomata</li><li>Leaf SA<br></li><li>Light Intensity</li></ul> When describing a graph linking two variables, what points do you include when describing their relationship?<div>STATE:</div><div><ul><li>Positive/Negative correlation?</li><li>Reaches a peak/plateau? When?</li><li>Correlation does not mean causation.</li><li>Other factors may be involved. </li></ul></div> Why does carrying out repeats allow for a more reliable mean?<ul><li>Spot anomalies</li><li>Calculate a mean such that any anomalies have less effect</li><li>Hence, mean is more reliable.</li></ul> Explain how CO<sub>2</sub> levels affects the rate of photosynthesis. [2] "<ul><li>When its low, conversion of RuBP to GP is <font color=""#ff0000"">slow </font>(there’s less CO2 to combine with RuBP to make GP)</li><li>The level of RuBP will rise (still being made) and levels of GP and TP will fall (used to make RuBP)</li></ul>" Suggest how water stress could affect the rate of photosynthesis in a plant.<ul><li>Plants don't have enough water - stomata will close to save the little water that they have</li><li>Less CO<sub>2</sub> will enter</li><li>Slower rate of Calvin Cycle (less CO2 to combine with RuBP)</li></ul> "SL: Organisms <span class=""cloze"" data-cloze=""increase their chance of surviva"" data-ordinal=""1"">[...]</span>l by <span class=""cloze-inactive"" data-ordinal=""2"">responding to changes in their environment. </span>""SL: Organisms <span class=""cloze"" data-ordinal=""1"">increase their chance of surviva</span>l by <span class=""cloze-inactive"" data-ordinal=""2"">responding to changes in their environment. </span><br> " "SL: Organisms <span class=""cloze-inactive"" data-ordinal=""1"">increase their chance of surviva</span>l by <span class=""cloze"" data-cloze=""responding to changes in their environment.&nbsp;"" data-ordinal=""2"">[...]</span>""SL: Organisms <span class=""cloze-inactive"" data-ordinal=""1"">increase their chance of surviva</span>l by <span class=""cloze"" data-ordinal=""2"">responding to changes in their environment. </span><br> " Describe innate behaviour. [3] <ul><li>Inherited</li><li>(often) automatic</li><li>May be involved in finding mates, food, suitable conditions etc. </li></ul> Define 'Taxis'. A <u>directional </u>movement response where the animal moves towards the stimulus or away from the stimulus. The response direction is determined by the direction of the stimulus.  Explain how IAA results in gravitropism in roots: [6]"<ul><li>Cells in root tip produce IAA; transported along the root by <b><font color=""#ff1f0f"">diffusion</font></b></li><li>IAA initially transported to all sides</li><li>Gravity causes IAA to move from upper side <font color=""#ff1f0f""><b>to lower side</b></font></li><li>Higher [IAA] on lower side</li><li>IAA inhibits elongation of root cells; lower side <font color=""#ff1f0f""><b>elongates / grows less</b></font></li><li>Root bends downwards to the force of gravity</li></ul>" Explain how IAA causes phototropism in the shoots. [6]"<ul><li>Cells in shoot tip produce IAA; transported down the shoot by <font color=""#ff1f0f"">diffusion</font></li><li>Initially transported <font color=""#ff1f0f"">evenly </font>throughout all regions</li><li>Light causes movement of IAA to from light side to <font color=""#ff1f0f"">shaded side</font></li><li>Greater [IAA] in shaded side</li><li>IAA causes elongation of shoot cells</li><li>Shaded side elongates faster; tip bends <font color=""#ff1f0f"">towards the light </font></li></ul><div><img src=""n8mCp7m.gif""><font color=""#ff1f0f""><br></font></div>" What is the role of specific growth factors in flowering plants?They move from growing regions to other tissues, where they regulate growth in response to directional stimuli.  Compare and contrast taxis and tropisms. MS [2] "<div>1.     Similarity − directional response (to a stimulus) / movement towards / away from a stimulus; </div> <div>2.     Difference − taxis (whole) organism moves and tropism a growth (response).</div>" Define receptor. "<div style=""text-align: left;"">a transducer which transforms the energy of the stimulus into another form of</div><div style=""text-align: left;"">energy which will lead to the organism responding to this. They are specific.</div>" Which disaccharide is a non-reducing sugar?sucrose Which disaccharides are reducing sugars?maltose<div>Lactose</div> What are the 4 stages of aerobic respiration?<ul><li>Glycolysis</li><li>Link Reaction</li><li>Krebs Cycle</li><li>Oxidative Phosphorylation / ETC </li></ul> Where does glycolysis occur?cytoplasm What type of process is glycolysis?anaerobic (no O<sub>2</sub> required) Recall the steps of glycolysis and draw the diagram. MS [6]"<div>1.     Glucose phosphorylated by ATP to give ADP and glucose phosphate;</div> <div>2.     ATP adds another phosphate to form hexose bisphosphate;</div> <div>3.     Split into 2 triose phosphates;</div> <div>4.     Each triose phosphate oxidised to pyruvate;</div> <div>5.     NAD forms reduced NAD (NADH) by accepting H; 1 per TP</div><div>6.     2 ATP formed per TP molecule (4 ATP total)</div><div><br></div><div style=""text-align: center;""><img src=""The_process_of_Glycolysis_(source_https---www.s-cool.co.uk-a-level-biology-respiration-revise-it-glycolysis_).gif""><br></div>" What are the net products of glycolysis per glucose molecule?<ul><li>2x ATP (2 used, 4 produced = 2 net gain)</li><li>2x NADH</li><li>2x Pyruvate </li></ul><div><div><br></div></div> Recall the steps in the link reaction. Draw a diagram.  [5] "<ul><li>oxidation of pyruvate; forms acetate</li><li>decarboxylation of pyruvate, CO<sub>2</sub> released</li><li>NAD reduced to form NADH</li><li>addition of CoEnzyme A to acetate</li><li>to form acetyl coenzyme A</li></ul><div style=""text-align: center;""><img src=""paste-a2f7f9c585cb1d4b66dd3f2e5b8ad99831fc5f24.jpg""><br></div>" Where does the link reaction occur?mitochondrial matrix How does pyruvate get from the cytoplasm to the mitochondrial matrix?active transport What are the products of the link reaction per glucose molecule?<ul><li>2 acetyl coenzyme A</li><li>2 CO<sub>2</sub> </li><li>2 NADH</li></ul><div>Remember that each glucose molecule forms 2 pyruvate molecules. Hence the link reaction occurs twice per glucose molecule. </div> What is a co-enzyme? <ul><li>Molecule that aids the functions of enzymes</li><li>by transferring a chemical group between molecules</li></ul> What are the 3 co-enzymes in respiration and their functions?<ul><li>NAD (tranfser H) </li><li>FAD (transfer H)</li><li>CoA (tranfsers acetate)</li></ul> Compare the number of carbons in an acetate molecule and pyruvate molecule.Pyruvate = 3C<div><br></div><div>Acetate = 2C</div><div><br>One C lost during carboxylation</div> Recall the steps in the Kreb's Cycle. Sketch a diagram. MS [6]"<div>1.     Acetyl CoA combines with 4C to form 6C, releases CoA</div> <div>2.     6C converted to 5C </div> <div>3.     decarboxylation and hydrogen removed by NAD to produce reduced NAD;</div> <div>4.     5C converted to 4C</div> <div>5.     decarboxylation and hydrogen removed by NAD/FAD to produce reduced NAD/FAD;</div> <div>6.     ATP produced through substrate level phosphorylation</div><div><br></div><div><img src=""The-Krebs-Cycle_1.png""><br></div>" What are the products of the Kreb's Cycle per glucose molecule?Cycle turns <b>twice </b>for each glucose molecule (remember 2x Acetyl Coenzyme A mols per glucose!)<div><br></div><div><ul><li>6x reduced NAD</li><li>2x reduced FAD</li><li>2x ATP</li><li>4x CO<sub>2</sub></li></ul></div> Recall what occurs during the ETC / Oxidative Phosphorlyation. MS [8]<ul><li>Electrons released from reduced NAD / FAD;</li><li>Electrons pass along carriers / through ETC</li><li>Releasing energy;</li><li>Energy used to actively transport protons into intermembrane space;</li><li>Establishes electrochemical gradient</li><li>H+ move by f.diffusion through ATP synthase back into matrix</li><li>Resulting in the formation of ATP: ADP + Pi --> ATP </li><li>O<sub>2</sub> is the final electron acceptor / H+, e- and O<sub>2</sub> form H<sub>2</sub>O</li></ul> Recall how lipids can be used an alternative respiratory substrate. [2]<ul><li>hydrolysed to glycerol and FA</li><li>glycerol phosphorlyated > triose phosphate</li></ul> Why do lipids release 2x the energy contained in carbohydrates when used in respo?make 2C fragments of carbohydrates and many H+ ions<br> Where does the ETC take place?the inner membrane of the mitochondria, along the cristae What is the source of e- in the ETC?<ul><li>H atoms carried by co-enzymes (FADH and NADH)</li><li>they're oxidised, release H: H -> H+ + e- </li></ul> Recall 2 ways to diagnose AIDs. MS [2]<ul><li>check for AIDs-related symptoms</li><li>Number of Th cells</li></ul> Why do electron microscopes have a higher resolution than optical microscopes?Electrons have a shorter wavelength.  Recall what happens to <b>pyruvate </b>in anaerobic conditions and explain why this is advantageous to <b>humans. </b>MS [5]<div><br></div><div><br></div>"<div>1.     Reduced to lactate;</div> <div>2.     Using reduced NAD;</div> <div>3.     Regenerates NAD;</div> <div>4.     NAD can be reused to allow glycolysis to continue; </div> <div>5.     Can still release energy/form ATP when oxygen in short supply;</div><div><br></div><div><br></div><div><img src=""Lactate-Fermentation.png""><br></div>" What are the two pathways for anaerobic respiration?<ul><li>ethanol fermentation (plants)</li><li>lactate fermentation (humans)</li></ul> Recall the ethanol fermentation pathway for Anaerobic Respiration. [3]"<ul><li>Pyruvate is decarboxylated to ethanal</li><li>Ethanal reduced to ethanol by enzyme alcohol dehydrogenase</li><li>NADH transfers its H to ethanal, which is a H acceptor</li></ul><img src=""Ethanol-Fermentation.png""><br>" What two things can happen to lactate after is it produced?<ul><li>Oxidised back to <b>pyruvate </b>- enters Link</li><li>Converted into <b>glycogen </b>for storage in the liver</li></ul> Why do animals breath deeper and faster after exercise? [3]<ul><li>Anaerobic respiration during exercise</li><li>Produces lactate, which is toxic / causes muscle fatigue </li><li>Oxidation of lactate back to pyruvate needs extra oxygen - <b>oxygen debt</b></li></ul> Recall how aerobic respiration stops functioning in the absence of oxygen.<ul><li>No <b>final acceptor of electrons </b>in ETC</li><li>ETC stops functioning</li><li>No more ATP via OxPhosp</li><li>NADH, FADH not oxidised by electron carrier (e- arent moving along)</li><li>No oxidised NAD+/FAD+ avaliable for Kreb's </li><li>Kreb's stops</li></ul> Why is less ATP produced in anaerobic respiration? [3]<ul><li>No ETC / OxPhospho</li><li>which produces majority of ATP</li><li>Only <b>glycolysis </b>occurs (net 2ATP per glucose)</li></ul> What is the importance of the regenerated molecule in the lactate/ethanol fermentation pathways? [2]<ul><li>NAD+ is regenerated</li><li>Used in further glycolysis</li></ul> Explain why an athlete's ATP is provided by anaerobic rather than aerobic respiration. MS [2]<ul><li>high respiration rate / energy demand is high</li><li>insufficient oxygen in muscles to aerobically respire</li></ul> Explain why athletes will breath heavily after a race. [2]<ul><li>lactate oxidised into pyruvate (repay oxygen debt)</li><li>by <u>aerobic </u>respiration</li></ul> What are the compounds in the Kreb's cycle?6C = Citrate<div>5C = Intermediate</div><div>4C = Oxaloacetate </div> Describe the piece of apparatus used to measure the rate of respiration. "<ul><li>Using a respirometer</li><li>Removal of O<sub>2</sub> in the tube reduced volume and pressure</li><li>Fluid moves toward the organism</li></ul> <img src=""PB_measuring-rate-of-metabolism-respirometer2-500.jpg""><br>" What is the purpose of soda lime in a respirometer?<ul><li>Absorbs CO<sub>2</sub> </li><li>Ensures movement is only due to the intake of O<sub>2</sub> </li></ul> "Muscles act in <span class=""cloze"" data-cloze=""antagonistic pairs"" data-ordinal=""1"">[...]</span> against an <span class=""cloze"" data-cloze=""incompressible skeleton"" data-ordinal=""1"">[...]</span>""Muscles act in <span class=""cloze"" data-ordinal=""1"">antagonistic pairs</span> against an <span class=""cloze"" data-ordinal=""1"">incompressible skeleton</span><br> " Recall how muscles work in antagonistic pairs. [5]<br>"<ul><li>Muscles can only pull</li><li>They work in opposing pairs (e.g hamstring + quads / biceps + triceps)</li><li>Contracting muscle = agonist</li><li>Relaxing muscle = antagonist</li><li>Muscle contracting becomes 'shorter' </li></ul><div><br></div><div><img src=""paste-8ebb0ad10c7edbc4ea796d20e85ef83732ebf81f.jpg""><br></div>" Recall how muscles help maintain posture. MS [5]<ul><li>Antagonistic muscles / opposing pairs;</li><li>Working across joints;</li><li>Both contract to keep joint / the body at a certain angle / upright;</li><li>Isometric contraction;</li><li>Only a few fibres contract to avoid fatigue / slow muscle fibres used; <br></li></ul> What are muscles?effector organs which respond to nervous stimulation by contracting What are muscle cells more commonly known as?myocytes (cells that make up muscle tissue) What are the 3 types of muscle cell and where are they found?<ul><li>cardiac - found only in the heart</li><li>skeletal - found in walls of gut / blood vessels</li><li>smooth - attached to our bones, under voluntary control </li></ul> (OFF SPEC) What are the adaptations of cardiac myocytes? [4]<ul><li>Myogenic</li><li>Branched (faster signal propagation)</li><li>Intercalated discs (cells not connected)</li><li>More mitochondria (reliant on aerobic respo)</li></ul> Contrast ligaments vs tendons.<ul><li>Ligaments = connect bone to bone</li><li>Tendons = connect bone to muscle</li></ul> What is a sarcomere?the basic unit of muscle contraction in a myofibril (which is in a muscle cell) Recall the divisions of a skeletal muscle. "<ul><li>Muscle Tissue - Bundles of Muscle Fibre - Single Muscle Fibre - Myofibrils - Sarcomere (basic unit)</li></ul><div><img src=""paste-614bb9768288fa34b931b9570b368c62944396b8.jpg""><br></div>" "<img src=""paste-e243b9afaac73122cf45e79fdd042ec0e8fa2cfd.jpg"">""<img src=""paste-51fded89817a2fa976774c876d2c6668278e63fd.jpg"">" Recall the structure of skeletal muscles. [4]"<ul><li>Skeletal muscles made up of many fibres called <font color=""#ff0000"">myofibrils</font>; which are divided into contractual units called <font color=""#ff0000"">sarcomeres</font></li><li>Muscle fibres fused together + <font color=""#ff0000"">share nuclei</font> and cytoplasm (<font color=""#ff0000"">sarcoplasm</font>)</li><li>Myosin + actin filaments <font color=""#ff0000"">overlap</font>, strenghtening the muscle</li><li>Sarcoplasm contains <font color=""#ff0000"">sarcoplasmic reticulum</font> + mithcondria</li></ul>" What is the difference between myofibrils and sarcomeres?<ul><li>Myofibrils = contracting units of muscles</li><li>Sarcomeres = repeating units of the myofibril</li></ul> Sketch a rough sarcomere. "<div><br></div><div><img src=""paste-849dba1d2fd17a9e75ba66edabe304211b4fd684.jpg""><br><br></div><div><br></div>" "<img src=""paste-650024379727bd1dd61a22db253e3ac8f3db8f14.jpg"">""<img src=""paste-7258b4c3763a8a247ed591c5fed456e467e13bca.jpg"">" What are the two types of muscle fibres?<ul><li>Slow twitch</li><li>Fast twitch</li></ul> How does the function of slow twitch fibres differ from fast twitch fibres? [3] <ul><li>ST contract more slowly; FT contract rapidly</li><li>ST provide less powerful contractions; FT powerfully contract</li><li>ST contract over longer periods of time = endurance work; FT adapted for intense exercise<br></li></ul> Recall the adaptations of ST muscle fibres. [3]<ul><li>Large myoglobin store (stores oxygen)</li><li>Rich supply of blood vessels (aerobic respiration)</li><li>Numerous mitochondria </li></ul> Recall the adaptations of FT muscle fibres. [4]<ul><li>Thicker, more numerous myofilaments</li><li>Higher [Glycogen]</li><li>Higher [Enzyme] involved in AnRes, provides ATP rapidly</li><li>Stores phosphocreatine</li></ul> "<div>What is the role of phosphocreatine (PC) in providing energy during muscle contraction? MS [2]</div>""<div>1.     provides phosphate;</div> <div>2.     To make ATP (ADP + CP → ATP + C ); </div>" Where would you find ST muscle fibres? Why?<ul><li>lower legs</li><li>muscle in the back</li></ul><div>helps you to stand / hold posture for long periods of time</div> Recall what is meant by Respiratory Quotient. What information can we deduce from it?RQ = Volume of CO<sub>2</sub> produced / Volume of O<sub>2</sub> absorbed<div><br></div><div>If:</div><div><ul><li>RQ > 1 implies mainly anaerobic respiration</li><li>RQ = 1 implies aerobic respo of glucose</li><li>RQ < 1 implies aerobic respo of another substrate (e.g lipids / proteins)</li></ul></div> Explain why, in terms of respiration, a trained organism would be able to exercise for a longer period of time than an untrained one. MS [3]<ul><li>(adaptations e.g more dehydrogenase means..) More ATP produced</li><li>Anaerobic respiration delayed</li><li>Less lactic acid (which would cause muscle fatigue) </li></ul> " <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""b2b8fc1aa5c44c77a995a8d990b9cb1a-ao-1-Q.svg"" /></div> <div id=""io-original""><img src=""paste-8b29ae6c02acba9727cdb36a47f77dc76fadf4e3.jpg"" /></div> </div> <div id=""io-footer""></div> <script> // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> "" <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""b2b8fc1aa5c44c77a995a8d990b9cb1a-ao-1-A.svg"" /></div> <div id=""io-original""><img src=""paste-8b29ae6c02acba9727cdb36a47f77dc76fadf4e3.jpg"" /></div> </div> <button id=""io-revl-btn"" onclick=""toggle();"">Toggle Masks</button> <div id=""io-extra-wrapper""> <div id=""io-extra""> </div> </div> <script> // Toggle answer mask on clicking the image var toggle = function() { var amask = document.getElementById('io-overlay'); 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} if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> " " <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""59da03aa97054caf9593f1b3c909f061-ao-5-Q.svg"" /></div> <div id=""io-original""><img src=""paste-8b29ae6c02acba9727cdb36a47f77dc76fadf4e3.jpg"" /></div> </div> <div id=""io-footer""></div> <script> // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> "" <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""59da03aa97054caf9593f1b3c909f061-ao-5-A.svg"" /></div> <div id=""io-original""><img src=""paste-8b29ae6c02acba9727cdb36a47f77dc76fadf4e3.jpg"" /></div> </div> <button id=""io-revl-btn"" onclick=""toggle();"">Toggle Masks</button> <div id=""io-extra-wrapper""> <div id=""io-extra""> </div> </div> <script> // Toggle answer mask on clicking the image var toggle = function() { var amask = document.getElementById('io-overlay'); if (amask.style.display === 'block' || amask.style.display === '') amask.style.display = 'none'; else amask.style.display = 'block' } // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> " " <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""59da03aa97054caf9593f1b3c909f061-ao-6-Q.svg"" /></div> <div id=""io-original""><img src=""paste-8b29ae6c02acba9727cdb36a47f77dc76fadf4e3.jpg"" /></div> </div> <div id=""io-footer""></div> <script> // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> "" <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""59da03aa97054caf9593f1b3c909f061-ao-6-A.svg"" /></div> <div id=""io-original""><img src=""paste-8b29ae6c02acba9727cdb36a47f77dc76fadf4e3.jpg"" /></div> </div> <button id=""io-revl-btn"" onclick=""toggle();"">Toggle Masks</button> <div id=""io-extra-wrapper""> <div id=""io-extra""> </div> </div> <script> // Toggle answer mask on clicking the image var toggle = function() { var amask = document.getElementById('io-overlay'); if (amask.style.display === 'block' || amask.style.display === '') amask.style.display = 'none'; else amask.style.display = 'block' } // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> " Use the string analogy to explain the organisation of a muscle fibre."<ul><li>Myofibrils (threads) make up a single muscle fibre (string)</li><li>These single muscle fibres group to make a bundle of muscle fibres (small rope)</li><li>Bundles of muscle fibre further grouped into muscle tissue (large rope)</li></ul><div><img src=""paste-a48682eb42a4f241f5025291b9a2d6252446b075.jpg""><br></div>" Why have the separate cells of muscles fused together to form fibres?<ul><li>If individual cells joined end-to-end; junction would be a point of weakness</li></ul> How are myofibrils arranged within a single muscle fibre?<ul><li>They are lined up parallel to each other</li><li>in order to give maximum force when contracting </li></ul> What is the sarcoplasm?cytoplasm shared between muscle fibre cells "<b><span style=""font-weight: 400;"">What is the role of </span>calcium ions <span style=""font-weight: 400;"">in myofibril contraction? MS [4]</span></b>""<b><div><span style=""font-weight: 400;"">1. Calcium ions diffuse into myofibrils from (sarcoplasmic) reticulum;</span></div><div><span style=""font-weight: 400;"">2. (Calcium ions) cause movement of tropomyosin (on actin);</span></div><div><span style=""font-weight: 400;"">3. (This movement causes) exposure of the binding sites on the actin;</span></div><div><span style=""font-weight: 400;"">4. Myosin heads can now attach to binding sites on actin; (to form an actinomyosin bridge</span></div></b><br>" "<b><span style=""font-weight: 400;"">What is the role of </span>ATP <span style=""font-weight: 400;"">in myofibril contraction? MS [3]</span></b>""<b><ul><li><b><div><span style=""font-weight: 400;"">Hydrolysis of ATP (on myosin heads) causes myosin heads to bend;</span></div></b></li><li><b><div><span style=""font-weight: 400;"">(Bending) pulling actin molecules; </span>power stroke</div></b></li><li><div><span style=""font-weight: 400;""> Attachment of a new ATP molecule to each myosin head causes myosin heads to detach (from actin sites).; </span>recovery stroke</div></li></ul></b><br>" "<b><span style=""font-weight: 400;"">What is the role of </span>ATPase <span style=""font-weight: 400;"">in myofibril contraction? MS [3]</span></b>""<b><div><span style=""font-weight: 400;"">1. Splitting/breakdown/hydrolysis of ATP;</span></div><div><span style=""font-weight: 400;"">2. (Muscle) contraction requires energy / ATP;</span></div><div><span style=""font-weight: 400;"">3. Use of ATP by myosin (to bend / detach)</span></div></b><br>" Recall the structure of myosin. [2]made up of two types of protein:<div><ul><li>fibrous protein (the tail)</li><li>globular protein forming two bulbous heads</li></ul></div> What type of protein is actin?globular Give an example of where you'd find a high proportion of ST muscle fibres.<ul><li>Calf Muscle</li><li>Contract constantly to maintain the body in an upright position. </li></ul> Give an example of where you'd find a high proportion of FT muscle fibres.<ul><li>Muscles that are adapted to high intensity exercise</li><li>Bicep muscles of the upper arm</li></ul> Recall what occurs during muscle relaxation. [4]<ul><li>Ca<sup>2+</sup> ions move by Atrans back to sarcoplasmic reticulum</li><li>Uses energy from ATP</li><li>Reabsorption of Calcium causes tropomyosin to block actin filament </li><li>Myosin heads no longer able to bind</li></ul><div><br></div><div>NB: MS will likely just say that ''ATP results in the detachment of myosin head from actin'' </div> Recall how muscular contraction is stimulated when an AP reaches the end of a motor neurone. [6]<ul><li>AP arrives at NMJ</li><li>Influx of Ca<sup>2+</sup> and release of acetyl choline (from presynapse)</li><li>Acetylcholine diffuses across cleft; binds to receptor sites on sarcolemma</li><li>Influx of Na+, causes AP in sarcolemma</li><li>Impulse carried through the muscle fibres through <b>T-tubules</b></li><li>Triggers release of Ca<sup>2+</sup> from sarcoplasmic reticulum </li></ul> "Plants synthesise organic compounds from <span class=""cloze"" data-cloze=""atmospheric or aquatic CO<sub>2</sub>"" data-ordinal=""1"">[...]</span>""Plants synthesise organic compounds from <span class=""cloze"" data-ordinal=""1"">atmospheric or aquatic CO<sub>2</sub></span><br> " "Most of the sugars synthesised by plants are used as <span class=""cloze"" data-cloze=""respiratory
substrates"" data-ordinal=""1"">[...]</span>. The rest are used to make other groups of biological molecules, forming the <span class=""cloze"" data-cloze=""biomass"" data-ordinal=""1"">[...]</span> of the plant.""Most of the sugars synthesised by plants are used as <span class=""cloze"" data-ordinal=""1"">respiratory substrates</span>. The rest are used to make other groups of biological molecules, forming the <span class=""cloze"" data-ordinal=""1"">biomass</span> of the plant.<br> " "Biomass is the <span class=""cloze"" data-cloze=""total mass of living material in a specific area at a given time"" data-ordinal=""1"">[...]</span>""Biomass is the <span class=""cloze"" data-ordinal=""1"">total mass of living material in a specific area at a given time</span><br> " "Dry biomass shows the <span class=""cloze"" data-cloze=""chemical energy store in an organism"" data-ordinal=""1"">[...]</span> and can be measured by the process of <span class=""cloze-inactive"" data-ordinal=""2"">calorimetry</span>""Dry biomass shows the <span class=""cloze"" data-ordinal=""1"">chemical energy store in an organism</span> and can be measured by the process of <span class=""cloze-inactive"" data-ordinal=""2"">calorimetry</span><br> " "Dry biomass shows the <span class=""cloze-inactive"" data-ordinal=""1"">chemical energy store in an organism</span> and can be measured by the process of <span class=""cloze"" data-cloze=""calorimetry"" data-ordinal=""2"">[...]</span>""Dry biomass shows the <span class=""cloze-inactive"" data-ordinal=""1"">chemical energy store in an organism</span> and can be measured by the process of <span class=""cloze"" data-ordinal=""2"">calorimetry</span><br> " "Gross primary production (GPP) is defined in words as <span class=""cloze"" data-cloze=""the chemical
energy stored in plant biomass, in a given area or volume"" data-ordinal=""1"">[...]</span>""Gross primary production (GPP) is defined in words as <span class=""cloze"" data-ordinal=""1"">the chemical energy stored in plant biomass, in a given area or volume</span><br> " "NPP is defined as <span class=""cloze"" data-cloze=""the chemical energy store in
plant biomass after respiratory losses to the environment have
been taken into account"" data-ordinal=""1"">[...]</span>""NPP is defined as <span class=""cloze"" data-ordinal=""1"">the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account</span><br> " "<span class=""cloze-inactive"" data-ordinal=""2"">NPP</span> = <span class=""cloze"" data-cloze=""GPP - R"" data-ordinal=""1"">[...]</span>""<span class=""cloze-inactive"" data-ordinal=""2"">NPP</span> = <span class=""cloze"" data-ordinal=""1"">GPP - R</span><br> " "<span class=""cloze"" data-cloze=""NPP"" data-ordinal=""2"">[...]</span> = <span class=""cloze-inactive"" data-ordinal=""1"">GPP - R</span>""<span class=""cloze"" data-ordinal=""2"">NPP</span> = <span class=""cloze-inactive"" data-ordinal=""1"">GPP - R</span><br> " What are the units for GPP, NPP + R?kJ m<sup>-2</sup> yr<sup>-1</sup> "The NPP is available for <span class=""cloze-inactive"" data-ordinal=""1"">plant growth and reproduction</span>. It is also available for <span class=""cloze"" data-cloze=""consumers in the food chain such as herbivores
and decomposers"" data-ordinal=""2"">[...]</span>.""The NPP is available for <span class=""cloze-inactive"" data-ordinal=""1"">plant growth and reproduction</span>. It is also available for <span class=""cloze"" data-ordinal=""2"">consumers in the food chain such as herbivores and decomposers</span>.<br> <img src=""paste-367f66e7aa8d9a9556986770b2df793e73c74b5e.jpg"">" "The NPP is available for <span class=""cloze"" data-cloze=""plant growth and reproduction"" data-ordinal=""1"">[...]</span>. It is also available for <span class=""cloze-inactive"" data-ordinal=""2"">consumers in the food chain such as herbivores and decomposers</span>.""The NPP is available for <span class=""cloze"" data-ordinal=""1"">plant growth and reproduction</span>. It is also available for <span class=""cloze-inactive"" data-ordinal=""2"">consumers in the food chain such as herbivores and decomposers</span>.<br> <img src=""paste-367f66e7aa8d9a9556986770b2df793e73c74b5e.jpg"">" "Net production (N) is <span class=""cloze"" data-cloze=""the total chemical energy consumers store
after energy losses to faeces, urine and respiration have been taken
away from the chemical energy store of the ingested plant food"" data-ordinal=""1"">[...]</span>""Net production (N) is <span class=""cloze"" data-ordinal=""1"">the total chemical energy consumers store after energy losses to faeces, urine and respiration have been taken away from the chemical energy store of the ingested plant food</span><br> " "Equation for Net Production:    <span class=""cloze"" data-cloze=""N = I - (F + R)&nbsp;<div><br></div><div><br></div><div>Where N is net production, I represents the total chemical
energy store in ingested food, F is the energy lost in faeces and
urine, and R is energy lost to respiration. All use units (kJ m-2 yr-1)</div>"" data-ordinal=""1"">[...]</span>""Equation for Net Production:    <span class=""cloze"" data-ordinal=""1"">N = I - (F + R) <div><br></div><div><br></div><div>Where N is net production, I represents the total chemical energy store in ingested food, F is the energy lost in faeces and urine, and R is energy lost to respiration. All use units (kJ m-2 yr-1)</div></span><br> " "Primary and secondary productivity is the <span class=""cloze"" data-cloze=""rate of primary or
secondary production, respectively"" data-ordinal=""1"">[...]</span>. It is measured as <span class=""cloze-inactive"" data-ordinal=""2"">biomass in a given area in a given time e.g. kJ ha–1 year–1</span>""Primary and secondary productivity is the <span class=""cloze"" data-ordinal=""1"">rate of primary or secondary production, respectively</span>. It is measured as <span class=""cloze-inactive"" data-ordinal=""2"">biomass in a given area in a given time e.g. kJ ha–1 year–1</span><br> " "Primary and secondary productivity is the <span class=""cloze-inactive"" data-ordinal=""1"">rate of primary or secondary production, respectively</span>. It is measured as <span class=""cloze"" data-cloze=""biomass in
a given area in a given time e.g. kJ ha–1 year–1"" data-ordinal=""2"">[...]</span>""Primary and secondary productivity is the <span class=""cloze-inactive"" data-ordinal=""1"">rate of primary or secondary production, respectively</span>. It is measured as <span class=""cloze"" data-ordinal=""2"">biomass in a given area in a given time e.g. kJ ha–1 year–1</span><br> " "Equation for the percentage efficiency of energy transfer between trophic levels:<div><br></div><div><span class=""cloze"" data-cloze=""<img src="paste-d570a5230cd1bb3e74632b39a459e5be456a8b42.jpg">"" data-ordinal=""1"">[...]</span><br></div>""Equation for the percentage efficiency of energy transfer between trophic levels:<div><br></div><div><span class=""cloze"" data-ordinal=""1""><img src=""paste-d570a5230cd1bb3e74632b39a459e5be456a8b42.jpg""></span><br></div><br> " How do farming practises increase efficiency of energy transfer to increase yields? [2]<ul><li>Reducing respiratory losses in a human food chain e.g reducing the movement / energy expenditure of farm animals</li><li>Simplifying food webs to reduce energy losses to non-human food chains e.g killing weeds + pests using herbicides and insecticides </li></ul> There is a {{c1::finite supply of nutrients}} on Earth, which are recycled within {{c2::natural ecosystems}}.  Why do organisms need nitrogen?Source to manufacture:<div><ul><li>nucleic acids</li><li>proteins</li><li>nitrogen-containing compounds</li></ul></div> How do plants take in nitrogen?nitrate ions in the soil How do animals obtain most of their nitrogen-containign compounds?eating + digesting plants " <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""3c03e78017554758927ded09464a827b-ao-1-Q.svg"" /></div> <div id=""io-original""><img src=""paste-3c5a4fa7ee780af6acd7ac935d0393798c63de67.jpg""></div> </div> <div id=""io-footer""></div> <script> // Prevent original image from loading before mask aFade = 50, qFade = 0; 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if (amask.style.display === 'block' || amask.style.display === '') amask.style.display = 'none'; else amask.style.display = 'block' } // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> " " <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""3c03e78017554758927ded09464a827b-ao-3-Q.svg"" /></div> <div id=""io-original""><img src=""paste-3c5a4fa7ee780af6acd7ac935d0393798c63de67.jpg"" /></div> </div> <div id=""io-footer""></div> <script> // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> "" <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""3c03e78017554758927ded09464a827b-ao-3-A.svg"" /></div> <div id=""io-original""><img src=""paste-3c5a4fa7ee780af6acd7ac935d0393798c63de67.jpg"" /></div> </div> <button id=""io-revl-btn"" onclick=""toggle();"">Toggle Masks</button> <div id=""io-extra-wrapper""> <div id=""io-extra""> </div> </div> <script> // Toggle answer mask on clicking the image var toggle = function() { var amask = document.getElementById('io-overlay'); if (amask.style.display === 'block' || amask.style.display === '') amask.style.display = 'none'; else amask.style.display = 'block' } // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; 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if (amask.style.display === 'block' || amask.style.display === '') amask.style.display = 'none'; else amask.style.display = 'block' } // Prevent original image from loading before mask aFade = 50, qFade = 0; var mask = document.querySelector('#io-overlay>img'); function loaded() { var original = document.querySelector('#io-original'); original.style.visibility = ""visible""; } if (mask === null || mask.complete) { loaded(); } else { mask.addEventListener('load', loaded); } </script> " "Recombinant DNA technology involves <span class=""cloze"" data-cloze=""the transfer of fragments of
DNA from one organism, or species, to another"" data-ordinal=""1"">[...]</span>""Recombinant DNA technology involves <span class=""cloze"" data-ordinal=""1"">the transfer of fragments of DNA from one organism, or species, to another</span><br> " Why can transferred DNA be translated within cells of the transgenic organism?genetic code is universal, as are transcription and translation mechanisms What is recombinant DNA?"<b><span style=""font-weight: 400;"">DNA of two different species / two </span><u>types </u><span style=""font-weight: 400;"">of organisms that has been combined </span></b>" What are the 3 methods of producing DNA fragments?<ul><li>conversion of mRNA to cDNA using reverse transcriptase</li><li>using restriction enzymes to cut a fragment containing the desired gene from DNA</li><li>creating the gene in a 'gene machine'</li></ul> Recall how reverse transcriptase can be used to isolate a gene. [6]"<ul><li><b><div style=""display: inline !important;""><span style=""font-weight: 400;"">Cells that produce a large amount of mRNA for a required protein are identified</span></div></b></li><li><b><div style=""display: inline !important;""><span style=""font-weight: 400;"">Cells centrifuged to break open + release mRNA</span></div></b></li><li><b><div style=""display: inline !important;""><span style=""font-weight: 400;"">Free DNA nucleotides added to mRNA</span></div></b></li><li><b><div style=""display: inline !important;""><span style=""font-weight: 400;"">cDNA strand formed using reverse transcriptase</span></div></b></li><li><b><div style=""display: inline !important;""><span style=""font-weight: 400;"">Enzyme hydrolyses the mRNA (ribonuclease H)</span></div></b><br></li><li><b><div style=""display: inline !important;""><span style=""font-weight: 400;"">mRNA and cDNA now separated, single strand of cDNA</span></div></b></li><li><b><div style=""display: inline !important;""><span style=""font-weight: 400;"">DNA polymerase then catalyses formation of complementaty strand to the cDNA; producing a double helix of DNA</span></div></b></li></ul><div><img src=""paste-62d6c1f0d75b0564ed8dcbc2ee0861ffdd014cee.jpg""><br></div><br>" What are endonucleases?Enzymes produced by bacteria to cut up viral DNA as a defensive measure  Recall how restriction endonucleases can be used to produce DNA fragments."<ul><li>Cut DNA at specific sites, about 4-8 base pairs long, called<font color=""#ff0000""><b> recognition sites</b></font></li><li>Recognition sites are usually <font color=""#ff0000""><b>palindromic</b></font></li><li>RE makes staggered cuts will leave exposed bases on either end (sticky ends)</li></ul>" Recall how we use a 'gene machine' to produce DNA fragments."<ul><li>Sequence of bases determined</li><li>Triplets worked out + fed into computer</li><li>Computer designs <b><font color=""#ff0000"">oligonucleotides</font></b>, which are assembled into the desired gene</li></ul>" Once we have synthesised a gene, how is it amplified <i>in vitro</i>?PCR (polymerase chain reaction) Draw a diagram that summarises the nitrogen cycle. "<img src=""paste-3ff996601a4b39d2c21bc5e5ed3bbe656cfc0b60.jpg"">" What are mycorrhizae?"<ul><li>Certain types of fungi associate with roots of plants</li><li>Increase SA for absorption of water + mineral ions</li></ul><div><br></div><div><img src=""kWO1zcDVYWFQ7L7Phf7PGJXluqw_dKpzFcFXSDGqybvrGYY0xRTnS4VXv61TY86wlU9x9kMPqxsjbK0F54MXHX64aTUzV1qSE-A1UgasiiPVFwRRXjq.png""><br></div>" What are the 4 stages of the Nitrogen Cycle?<ul><li>Nitrogen Fixation</li><li>Ammonification</li><li>Nitrification</li><li>Denitrification</li></ul> Recall what occurs during nitrogen fixation. <ul><li>N<sub>2</sub> converted to N-containing compounds</li><li>by nitrogen-fixing bacteria (either mutalistic or free-living)</li></ul> Recall the two types of nitrogen-fixing bacteria and their functions."<div><b><u>Free-Living:</u></b></div><div><ul><li>Reduce N<sub>2</sub> into <font color=""#ff0000"">ammonia</font>, which are used to make AA. </li></ul><div><b><u>Mutualistic:</u></b></div></div><div><ul><li>Use N<sub>2</sub> to produce AA. </li><li>Mutualistic: because they obtain Carbohydrates from plants; plants obtain AA from bacteria</li></ul></div>" Recall ammonification. [3]"<ul><li>The production of <font color=""#ff0000"">ammonia </font>from organic N-containing compounds</li><li><font color=""#ff0000"">Saprobiontic micro-organisms</font> feed on <b>faeces </b>+ <b>dead organisms</b></li><li>Releasing <font color=""#ff0000"">ammonia </font>which then form ammonium ions in the soil. </li></ul>" Recall Nitrification."<ul><li>Ammonium ions are oxidised to produce to <b>nitrites </b>then oxidised to <b>nitrates <font color=""#ff0000"">(two stage oxidation reaction)</font></b></li><li>by nitrifying bacteria</li></ul><div><br></div><div><img src=""paste-e7d0024677ace952467f1c70e29cdbad1e2bbe60.jpg""><br></div>" Recall Denitrification.<ul><li>Nitrates are converted back to N<sub>2</sub> gas</li><li>by anaerobic, denitrifying bacteria<br></li><li>Not useful as N<sub>2</sub> cannot be absorbed by plants</li></ul> Why does waterlogging reduce nitrate content in the soil?<ul><li>Type of micro-organism changes</li><li><b>Fewer </b>aerobic nitrifying and nitrogen-fixing bacteria</li><li><b>More </b>anaerobic denitrifying bacteria</li><li>Convert nitrates into gaseous nitrogen </li></ul> Besides the nitrogen cycle, what are the 2 other ways nitrogen can be fixed?<ul><li>Lightning (fixes N<sub>2</sub> into nitrogen oxides)</li><li>Artificial fertilisers (haber process)</li></ul> Why is phosphorous essential?to form DNA, ATP, RNA and Phospholipid Bilayers (in CSM) Explain how farming practices increase the productivity of agricultural crops MS [5]<ul><li>Fertilisers / minerals added to soil</li><li>Nitrate / nitrogen for proteins OR Phosphate / phosphorous for ATP / DNA</li><li>Selective breeding / genetic modification of crops</li><li>Ploughing/aeration allows nitrification / decreases denitrification</li><li>Benefits of crop rotation / increases soil nutrients</li></ul> What are saprobiontic micro-organisms?<ul><li>Microorganisms that feed on faeces and dead matter</li><li>Releasing ammonia, which forms ammonium ions in the soil</li></ul> Describe how the action of micro-organisms in the soil produces a source of nitrates for crop plants. MS [7]<ul><li>Protein / AA / DNA into ammonium compounds / ammonia</li><li>by saprobionts</li><li>Ammonium into nitrite</li><li>Nitrite into nitrate</li><li>by nitrifying bacteria (microorganisms)</li><li>Nitrogen to ammonia</li><li>by nitrogen-fixing bacteria </li></ul> Draw the phosphorous cycle. "<img src=""paste-a10bdcbdca780425c97524440742fc2f2f9173cd.jpg"">" Recall the steps in the Phosphorous Cycle. <ul><li>PO<sub>4</sub><sup>3- </sup> released by rocks into the soil due to weathering/erosion</li><li>Plants absorb these phosphate ions</li><li>Animals eat + digest these plants and use these ions to synthesise organic matter</li><li>Excess PO<sub>4</sub><sup>3- </sup> are excreted by animals</li><li>On death, decomposers (some fungi + bacteria) break these animals down releasing PO<sub>4</sub><sup>3- </sup> to water / soil</li><li>PO<sub>4</sub><sup>3- </sup> found in bones/shells, but slow release<br></li><li>Some PO<sub>4</sub><sup>3- </sup> is transported by streams / lakes where they form sedimentary rocks</li></ul> Why are fertilisers needed?to replace nitrates + phosphates lost by harvesting plants and removing livestock What are the two types of fertilisers?<ul><li><b>Natural </b>- dead/decaying remains of plants/animals (manure, slurry and bone meal)</li></ul><div><br></div><ul><li><b>Artificial </b>- mined from rocks before being converted into different forms with their composition tailored for specific crops.</li></ul> What are the 3 negative effects of using fertilisers?<ul><li>Reduced species diversity</li><li>Leaching (polluting waterways)</li><li>Eutrophication</li></ul> How does the use of N-containing fertilisers reduce species diversity?<ul><li>N-rich soil favours rapidly growing species e.g grasses/nettles</li><li>Out-compete other species</li></ul> What is leaching?<ul><li>Process by which nutrients are removed from the soil</li><li>Find their way into watercourses (streams, rivers)</li><li>Can have a harmful effect on humans if the lake is a source of drinking water</li></ul> Recall the process of eutrophication and how it leads to the death of aquatic organisms. [6]"<ul><li>Mineral ions leached from fertilised fields stimulate rapid growth of algae/plants</li><li>Algae become more densely populated on upper surfaces / <font color=""#ff0000"">algal bloom</font></li><li>Absorbs light / prevents it from reaching plants below</li><li>Plants at the bottom die / unable to photosynthesise</li><li>Saprobiontic bacteria feed on dead plant matter - populations grow</li><li>Bacteria aerobically respire, using up oxygen</li><li>Fish and other aquatic organisms die because there isn't enough dissolved oxygen</li></ul>" What are the 2 ways in which gene cloning can be carried out?"<ul><li>in vivo - genes inserted into organism that produces copies during normal DNA replication</li><li>in vitro - genes duplicated in a machine using enzymes and rapid temperature changes (e.g PCR)</li></ul><div><br></div><div><img src=""Vyfw8D9Vm1uyG0WZzonRLPvOep5nABNAk3tiENOIjsJpWU7bnTFob_mbTeCZpzCghLZaFkG8KQEqRmBaTDdsRuNONQ.png""><br></div>" Sticky ends are used in genetic engineering. Explain how. MS [2]<ul><li>Joining two pieces of DNA;</li><li>By complementary binding/complementary base-pairing;</li></ul> Why are the same restriction endonucleases used to cut the DNA and the vector?ensures the sticky ends of the gene + plasmid are <u>complementary </u>to each other  What is the promoter region?<ul><li>sequence within DNA where RNA polymerase binds</li><li>required in order to begin transcription</li></ul> What is the terminator region?"<ul><li>sequence within DNA that causes RNA polymerase to be released and ends transcription</li></ul><div><br></div><div><img src=""paste-0331722c6b52bcc43e3fd8b0c98b1ac5c306abca.jpg""><br></div>" What is a vector? MS [2]<ul><li>Carrier of DNA</li><li>into cell / host / other organism</li></ul> What is the statistical conclusion if p value is equal to 0.05?<ul><li>Accept null hypothesis</li><li>Probability due to chance is 5%</li><li>Therefore, no significant difference / correlation</li></ul> Describe how PCR is carried out. MS [9]<ul><li> DNA heated to 90 to 95°C;</li><li> strands separate;</li><li> cooled / to temperature below 70°C </li><li> primers bind;</li><li> nucleotides attach;</li><li> by complementary base pairing;</li><li> temperature 70 - 75°C;</li><li> DNA polymerase joins nucleotides together;</li><li> cycle repeated;</li></ul> What is the role of primers in PCR?enables replication to start by keeping strands separate Recall the 5 stages involved in genetic engineering1. Isolation: genes isolated<div>2. Insertion: insertion of gene into a vector</div><div>3. Transformation: transfer of DNA into a host</div><div>4. Identification: analysing to see which host cells have taken up gene using gene markers</div><div>5. Growth/cloning: population of host cells rapidly increased</div> Recall how a gene is inserted into a plasmid vector.<ul><li>Sticky ends are complementary (since same REnds are used)</li><li>Promoter and terminator regions are added</li><li>DNA ligase forms 2 phosphoidester bonds</li></ul> What is the potential problem with the gene of interest/plasmid having the same sticky ends?"Mismatch - self coiling of plasmid / gene inserted has combined to form new piece of DNA (circularised DNA)<div><br></div><div><img src=""paste-ee828b362f5b3691f2df25cf842e0b347b0fdd94.jpg""><br></div>" What are the two methods of transformation? (insertion of vector into bacteria)<ul><li>Calcium ions added + heat shock</li><li>Electroporation</li></ul> Recall how calcium ions + heat shock are used to insert a vector into a bacteria.<ul><li>Calcium ions added</li><li>Cells heat shocked</li><li>Increases permeability of membrane</li></ul> Recall how electroporation is used to insert a vector.<ul><li>DNA negatively charged</li><li>Small electrical field increases permability</li><li>Causes movement of vector into host</li></ul> Why do only a small % of host cells have the required vector? [2]<ul><li>Not all plasmids incorporate donor DNA during insertion </li><li>Not all cells incorporate vectors during transformation</li></ul> What are the 3 methods of identifying which host cells have taken up the vector?<ul><li>GFP tagging</li><li>Enzyme marker</li><li>Antibiotic resistance: insertion and disruption</li></ul> How is GFP tagging used to identify desired host cells?"<ul><li>DNA sequence for GFP inserted into plasmid/donor DNA</li><li>Will light up green</li></ul><div><img src=""paste-782a9c2c0d3663c0963638a2afe1f24eb034c83b.jpg""><br></div>" How are enzyme markers used to identify transgenic host cells?<ul><li>Sequence for enzyme inserted / disrupted in either plasmid or donor DNA</li><li>E.g lactase is disrupted by insertion of DNA</li><li>Lactase turns colourless substrate blue hence transgenic bacteria will be clear colonies</li></ul> What is combination gene marking?<ul><li>GFP / enzyme marker added to both plasmid DNA and Donor DNA</li><li>Allows us to identify hybrid plasmid</li></ul> What is replica plating?<ul><li>Technique used to identify transgenic host cell</li><li>Plasmid used contains two antibiotic resistance genes</li><li>One of these is used as the site of <b>insertion </b>and is <b>disrupted</b></li><li>Add both antibiotics to samples of bacteria</li><li>Bacteria w/ recombinant plasmid will be resistant to one, but not the other</li></ul> What does NAD stand for?nicotinamide adenine dinucleotide How do yeast cells replicate?budding  Manometer / respirometer: Explain why the apparatus is left for 10 minutes to calibrate MS [3]1. Equilibrium reached<div>2. Allow for expansion / pressure change in apparatus</div><div>3. Allow for respiration rate to stabilise </div> Respirometer / Manometer: Why X temperature used?1. Optimum temp for normal growth of Y<div>2. Optimum temp for respiratory enzymes </div> Respirometer / Manometer: Explain why fluid moves towards organism.Oxygen taken up<div>CO2 given out is absorbed by KOH</div><div>Pressure decrease in B</div> What happens to the length of the A band during muscle contraction?remains unchanged in length What happens to the length of the I band during muscle contraction?<div><br></div>decrease in length What happens to the length of the H zone during muscle contraction?decrease in length Explain why the diversity of animal species higher at point B than at A. MS [2]More niches<div>More food <u>sources</u></div> Meiosis occurs during the life-cycle of organisms. Why is it so important? [2]Meiosis allows chromosome number to halve<div>Allows full number (diploid) to be restored during fertilisation </div> What is genetic fingerprinting?"A technique which uses the <b>individuality of DNA </b>molecules to distinguish between organisms or show the relationship between them. Consists of PCR + Gel electrophoresis. <div><br></div><div><br></div><div><img src=""paste-e6079429639114a6e60853a73f9ee8c44f9a132a.jpg"">  <br></div><div><br></div><div><img src=""paste-d1023e2d99c679802729a3178cd843336d86543b.jpg""><br></div>" What are VNTRs?"<ul><li>Regions found in the <font color=""#ff0000"">non-coding part of DNA</font></li><li>Contain <font color=""#ff0000"">variable numbers</font> of repeated DNA sequences and vary between diff people</li><li>VNTR may be referred to as 'satellite' or 'mini-satellite' DNA</li></ul><div><img src=""paste-0111eca92330d99b2c5772bdb94872d002b1c2e3.jpg""><br></div>" How are differences between VNTRs detected?<ul><li>DNA sequences amplified via PCR</li><li>Sample separated by size via gel electrophoresis</li></ul> Recall the process of genetic fingerprinting. MS [9]"<ol><li>DNA extracted from sample;</li><li>DNA cut / hydrolysed into segments using restriction endonucleases;</li><li>must leave minisatellites / required core sequences intact;</li><li>DNA fragments separated using electrophoresis;</li><li>detail of process e.g. mixture put into wells on gel and electric current passed through;</li><li>immerse gel in alkaline solution<font color=""#ff0000""> hence two strands of DNA separated</font>;</li><li>Southern blotting / cover with nylon / absorbent paper (to absorb DNA);</li><li><b>radioactive </b>marker / probe added  / complementary to VNTRs;</li><li>(areas with probe) identified using X-ray film / <b>autoradiography</b>;</li></ol><div><br></div><div><font color=""#ff0000"">NB: Allows DNA probes to attach</font></div>" The probability of two individuals having the same VNTRs is...very low unless they're identical twins Recall 4 uses of genetic fingerprinting.<ol><li>Identifying genetic relationships in paternity test</li><li>Matching DNA from a crime scene to suspects</li><li>Diagnosing diseases like Huntington's (based on number of AGC repeats on chromosome 4)</li><li>Prevent undesirable inbreeding in farms or zoos. </li></ol> What is a DNA probe?short, single-stranded length of DNA that is complementary to a known base sequence What are the two common forms of DNA probes?<ul><li>Radioactively labelled probes - made up of nucleotides with isotope P<sup>32</sup> . Identified via X-ray film.</li><li>Fluorescent labelled probes - emit light under certain conditions</li></ul> How are DNA probes used to locate specific alleles of genes?<ol><li>Sequence for mutated allele identified</li><li>Probe made with complementary bases</li><li>Probe is labelled (fluorescent or radioactive) then replicated</li><li>DNA sample obtained</li><li>DNA made single stranded by heating</li><li>Probe added; joins by complementary base pairings. </li><li>Wash to remove unattached probes</li><li>Can now identify using X-ray imaging or UV light</li></ol> What are the 4 main uses of DNA probes?<ul><li>Genetic screening for diseases</li><li>Personalised medicine; choosing most effective treatments</li><li>Genetic counselling</li><li>Genetic fingerprinting</li></ul> Recall how DNA probes are used in genetic counselling.<ul><li>Look at family history</li><li>If high risk, genetic probes can be used to screen for a disorder</li><li>Advice given to patients on preventative measures / lifestyle </li></ul> Recall how DNA probes are used in personalised medicine."<ul><li>Most diseases caused by range of mutations</li><li><font color=""#ff0000"">Different mutations</font> = different mechanisms hence we can tailor treatment to specific mutation</li><li>Some people's genes mean <font color=""#ff0000"">certain drugs are more/less effective</font> (e.g a particular form of enzyme needed)</li></ul>" What is gene therapy?treating genetic disease by providing the sufferer with a corrected copy of their defective gene What are the two methods of gene therapy currently used?1. Somatic cell therapy (body cells)<div>2. Germ line therapy (gametes)</div> What are the 2 methods of delivery in gene therapy? 1. Viral vectors;<div>2. Liposomes</div> What are liposomes?Lipid filled vesicles<div>are able to fuse into the CSM to insert a vector into the nucleus</div> What are the drawbacks to somatic cell therapy? [4]<div><ul><li>Cells need to be successfully reintroduced</li><li>Only directly altered cells are affected </li><li>Does not fix faulty function as original cells still remain.</li><li>Viral vector could mutate and become infectious</li></ul></div> Recall the advantages and disadvantages of germ line therapy. <div>A;</div><div>Potentially more effective;</div><div>All the cells of a person are easily accessible;</div><div>Possible to prevent inheritance;</div><div><br></div><div>D:</div><div>Safety & Ethical issues</div> Why does structure and function vary between somatic cells; even though DNA is identical?<div><ul><li>Only the relevant genes are active in a given cell at a given time (as a result of cell specialisation). </li><li>The rest are inhibited because their transcription and/or translation is switched off</li></ul></div> What is a stem cell?undifferentiated cell with the potential to become a wide variety of cells. Besides their ability to differentiate, what is another key ability of stem cells?able to replicate very rapidly  What is differentiation?the process by which stem cells divide and become specialised What's important to note about the division of totipotent cells during development?They only translate a part of their DNA, resulting in their specialisation.  What are totipotent stem cells?Stem cells that are able to differentiate into any type of cell Where are totipotent stem cells found in mammals?early embryo What are pluripotent stem cells?Stem cells that differentiate into almost any type of cell, besides placental cells.  Where are pluripotent stem cells found?in the embryo and fetus What are multipotent stem cells? Give examples."<ul><li>Stem cells that can differentiate into a <font color=""#ff0000"">limited number </font>cell types.</li><li>e.g adult stem cells or placental stem cells</li><li>Used for growth, repair, replacing </li></ul>" What are unipotent stem cells? Give an example. Stem cells that can differentiate into only a single type of cell<div><br></div><div>e.g cardiomyoblasts can only differentiate into cardiomyocytes</div> Evaluate the use of multipotent adult stem cells.A:<div>1. not rejected by the body;</div><div><br></div><div>D:</div><div>1. can become only a few types of cells;</div><div>2. risky/difficult procedure</div> Evaluate the use of plancetal/umbilical multipotent stem cells.1. Not rejected by the body<div><br></div><div>2. Can become a few types of cells</div><div>3. Only useful for future patients that have these cells harvested;</div> Evaluate the use of totipotent embryonic stem cells.<div>A:</div>1. Can become any cell; advantageous for tissues that do not have adult stem cells e.g nervous system<div><br></div><div>D:</div><div>1. ethical objections;</div><div>2. difficult matching / preventing rejections</div><div>3. rapid division could form tumour</div> "Totipotent cells occur only for <span class=""cloze"" data-cloze=""a limited time"" data-ordinal=""1"">[...]</span> in <span class=""cloze"" data-cloze=""early mammalian embryos"" data-ordinal=""1"">[...]</span>. ""Totipotent cells occur only for <span class=""cloze"" data-ordinal=""1"">a limited time</span> in <span class=""cloze"" data-ordinal=""1"">early mammalian embryos</span>. <br> " Where are multipotent and unipotent stem cells found?in mature mammals What are induced pluripotent stem cells?A type of <b>pluripotent </b>cell that is produced from unipotent stem cells by using protein transcription factors to express pluripotency-associated genes.  How do we turn specialised cells back into stem cells?<ul><li>Inducing genes and transcriptional factors within the cell within the cell to express themselves</li><li>(i.e turning on genes that were otherwise turned off)</li></ul> Give 3 examples of changes that occur during cell specialisation.<ul><li>Cell shape</li><li>Number of organelles</li><li>New cell content</li></ul> Where do we find stem cells in plants?<ul><li>Meristem cells in stem / root / shoot</li></ul> How is plant cloning achieved using stem cells? [1]<ul><li><b>Cuttings </b>taken from plants (shoot) - grows into genetically identical plants. </li></ul> What is homeostasis?The maintenance of constant internal environment within a living organism What does homeostasis involve in mammals?Physiological control systems that maintain the internal environment within restricted limits Via what systems is homeostasis controlled?"<ul> <li>The nervous system</li> <li>The endocrine system</li> <li>A combination of the two</li></ul>" What is meant by the term hormone?"<ul> <li>A chemical secreted by an endocrine gland</li> <li>Travels to all cells in the body in the blood</li> <li>Only affects cells in target tissues</li></ul>" How is heat lost in an organism?"<ul> <li>Breathing, urinating, defecating</li> <li>Mostly lost from the skin: <ul> <li>Evaporation</li> <li>Radiation</li> </ul> </li></ul>" What vessel governs vasoconstriction and vasodilation?Shunt vessel What mechanism returns systems to their normal level?Negative Feedback What are the different parts of a negative feedback system?"<ul> <li>A <font color=""#ff0000""><strong>receptor</strong> </font>(or sensor) – to <strong>detect</strong> a <strong>stimulus</strong> that is involved with a condition / physiological factor</li> <li>A <strong><font color=""#ff0000"">coordination system</font></strong> (nervous system and endocrine system) – to <strong>transfer information</strong> between different parts of the body</li> <li>An <font color=""#ff0000""><strong>effector</strong> </font>(muscles and glands) – to <strong>carry out a respon</strong></li></ul>" "Recall how the body responds to a large <span style=""font-weight:600""><font color=""#ff0000"">increase </font></span>in external temperature."<ol><li>hypothalamus (contains the thermoregulatory centre); </li><li>has receptors which detect temperature increase of blood; </li><li>receives impulses from receptors in skin;</li><li>nerve impulses transmitted (from hypothalamus / brain); </li><li>results in vasodilation / constriction of shunt vessels; </li><li>diversion of blood to skin surface; </li><li>sweating increases heat loss by evaporation;</li><li>no release of thyroxine / adrenaline; </li><li>no release metabolic rate / respiration; </li><li>correct reference to <b>negative feedback mechanisms</b>;</li></ol> "Recall how childbirth can be used as an example of positive feedback.<br><div><br></div><div><font color=""#ff00ff"">[Outside spec]</font></div><div><font color=""#ff00ff"">Synoptic Links: Hormones, Receptors</font></div>""<ul> <li>Baby head pushed onto cervix</li> <li>Cervix stretches</li> <li>Receptors detect the stretch, send impulses to the brain</li> <li>Oxytocin is secreted</li> <li>Oxytocin = increases in uterine contractions and baby pushed further onto cervix</li> <li>Stretches the cervix more</li></ul>" Define glycogenesissynthesis of glycogen from glucose Define glycogenolysisbreakdown of glycogen into glucose Define lipogenesisglucose converted into lipids What is the set point for BGC?~90mg/100cm3 blood Recall the Islets of Langerhans and its components."<ul> <li>Islets of Langerhans: tissue that acts as both receptors and endocrine cells </li><ul> <li>α cells = detect low glucose concentration and secrete glucagon</li> <li>β cells = detect high glucose concentration and secrete insulin</li> </ul></ul><img src=""IM01_Islets_of_Langerhans_v04.jpg""><br><ul> </ul>" Recall the action of insulin in lowering BGC. [7]"<ol><li>insulin binds to <font color=""#ff0000"">specific receptors </font>(on membranes);</li><li>insulin <font color=""#ff0000"">activates </font>carrier proteins / opens channels </li><li>insulin causes more glucose transporters to form via <font color=""#ff0000"">vesicle fusion</font></li><li>insulin increases the <font color=""#ff0000"">permeability </font>of liver / muscle cells / tissues to glucose;</li><li>glucose <font color=""#ff0000"">diffuses </font>into cells</li><li>insulin action activates <font color=""#ff0000"">enzymes </font>involved in glucose conversion to glycogen / glycogenesis;</li><li><font color=""#ff0000"">respiration </font>rate increases to use up more glucose</li></ol><div><br></div><div><br></div>" Recall the action of glucagon in increasing BGC.<ol><li>Attaches to specific receptors on the surfaces of liver cells</li><li>Activates enzymes involved in conversion of glycogen to glucose / glycogenolysis</li><li>Activates enzymes involved in conversion of glycerol and amino acids into glucose / gluconeogenesis</li></ol> What is the role of the liver in regulating blood sugar?Whilst the pancreas produces the hormones, it's in the liver where they have their effects. Three important processes occur:<br><ul><li>Glycogenesis</li><li>Glycogenolysis</li><li>Gluconeogenesis</li></ul> Recall the mode of action of adrenaline when BGC is low.<ul><li>Attach to receptors on CSM of a liver cell</li><li>Activates enzymes involved in the conversion of glycogen to glucose (glycogenolysis)</li></ul> Recall the second messenger model of adrenaline and glucagon action."<ol><li>Adrenaline / glucagon bind to specific receptors on cell membrane</li><li>Activate <font color=""#ff0000"">adenylate cyclase</font></li><li>Converts ATP to <font color=""#ff0000"">Cyclic AMP</font> (CAMP)</li><li>cAMP activates <font color=""#ff0000"">protein kinase A</font></li><li>Protein kinase A activates an enzyme cascade to break down glycogen to glucose (glycogenolysis)</li></ol>" What causes Type I diabetes?<ul><li>Genetic mutation</li><li>Results in autoimmune response to B-cells in Islets of Langerhans</li><li>Body can't produce as much insulin</li></ul> What causes Type II diabetes?<ul><li>Poor diet / obesity</li><li>Glycoprotein receptors on body cells lose their resonsiveness to insulin</li><li>Cells less responsive to insulin hence less glucose taken up </li></ul> How is Type I diabetes controlled by insulin?<div><ul><li>Injection insulin (not taken orally as protein is digested)</li><li>Insulin dosage matched to glucose intake </li></ul></div> How is Type II diabetes controlled by insulin?<ul><li>Use of drugs which target insulin receptors</li><li>Results in more glucose uptake by cells / tissues </li><li>e.g Metformin</li></ul> How is Type I diabetes controlled by diet manipulation?<ul><li>Eating regularly</li><li>Control of carbohydrate intake</li><li>Avoid sudden rise in glucose</li></ul> How is Type II diabetes controlled by diet manipulation?"<div><ul><li><div style=""display: inline !important;""><b>Reduced sugar intake / eat foods with low glyceamic index</b></div></li><li><font color=""#ff0000"">(less sugar absorbed into blood)</font></li><li><b>Reduced fat intake </b></li><li><font color=""#ff0000"">(less fat converted to glucose)</font></li><li><b>More (regular) exercise</b></li><li><font color=""#ff0000"">(uses glucose / fats by increasing respiration)</font></li><li><b>Lose weight</b></li><li><font color=""#ff0000"">(increased sensitivity of cells to insulin / increased uptake of glucose by cells)</font></li></ul></div>" Gene mutations occur {{c1::spontaneously}} during the process of {{c2::DNA replication}}.  What are mutagenic agents?"Chemical, physical or biological agents that <font color=""#ff0000"">increase the rate of mutation</font>. <div><br></div><div>e.g UV light, ionising radiation, benzopryene</div>" What is meant by an inversion mutation?"A sequence of bases detaches and rejoins in the same position back to front (inverse order)<div><br></div><div><br></div><div><img src=""paste-b755526feba7a7c86d202f4d8e8f8105eca1a05a.jpg""><br></div>" What is meant by a duplication mutation?"One or multiple bases are repeated; causing a frameshift. <div><br><div><img src=""paste-078249c9ed1e9702361e2a07d96d6bc2e9411694.jpg""><br></div></div>" What is a translocation mutation?"<ul><li>Group of bases become separated on one chromosome</li><li>Inserted into the DNA sequence of a different chromosome</li></ul><div><br></div><div><img src=""paste-e48013f0bf03bbd5ad97cc04c1cf3181281893c7.jpg""><br></div>" What are the possible results of a mutation on an encoded protein? [3]<ul><li>Single point mutation; protein remain functional</li><li>Degenerate code; same AA coded for</li><li>Frameshift; all codons / AA downstream from the mutation are changed</li></ul> Explain how a mutation can result in a non-functional enzyme. MS [5]<ol><li>Change in the base sequence of DNA;</li><li>Leads to a change in the amino acid sequence / primary structure;</li><li>Change in position of hydrogen / ionic / disulphide bonds;</li><li>Leads to a change in the tertiary structure / active site (of enzyme)</li><li>Substrate no longer complemenetary / no E-S complexes form. </li></ol> How can pluripotent stem cells be used to treat medical disorders?These can replace cells hence can treat disorders like leukaemia and diabetes. What is a transcription factor?A protein that controls the transcription of genes by binding to a specific region of DNA.  What are the two types of transcription factors?<br><ul><li>Activators (help RNA polymerase bind)</li><li>Repressors (prevent RNA polymerase binding)</li></ul> What is epigenetics?"changes in DNA that alter the expression of genes without changing the base sequence of DNA itself. It involves the addition of chemical tags onto DNA or histones" How does RNAi control gene expression?by preventing translation What does siRNA stand for?small interfering RNA What do siRNA within RISC do? [3]"<ul><li>Bind to a molecule of mRNA containing a sequence of bases complementary to its own.</li><li><font color=""#ff0000"">mRNA hydrolysed / translation stopped</font></li><li>miRNA expression is deregulated in many human diseases including cancer => this offers opportunities as bio markers and novel therapies</li></ul>" What does miRNA within RISC do?<ul><li>Binds to complementary sequence on mRNA</li><li>Prevents the attachment of the mRNA to ribosome</li><li>Prevents translation </li></ul> Besides vaccination production, what are possible applications of whole genome sequencing?phylogeny "Sequencing methods are continuously <span class=""cloze"" data-cloze=""updated"" data-ordinal=""1"">[...]</span> and have become <span class=""cloze-inactive"" data-ordinal=""2"">automated</span>""Sequencing methods are continuously <span class=""cloze"" data-ordinal=""1"">updated</span> and have become <span class=""cloze-inactive"" data-ordinal=""2"">automated</span><br> " "Sequencing methods are continuously <span class=""cloze-inactive"" data-ordinal=""1"">updated</span> and have become <span class=""cloze"" data-cloze=""automated"" data-ordinal=""2"">[...]</span>""Sequencing methods are continuously <span class=""cloze-inactive"" data-ordinal=""1"">updated</span> and have become <span class=""cloze"" data-ordinal=""2"">automated</span><br> " Compare and contrast anaerobic respiration in yeast cells vs muscle cells. MS [6]Similarities:<div>1. ATP formed / used;</div><div>2. Pyruvate formed/reduced;</div><div>3. Reduced NAD;</div><div>4. Glycolysis involved;</div><div><br></div><div>Differences:</div><div>1. Ethanol formed by yeast; lactate formed by muscle cells</div><div>2. CO2 produced by yeast, no CO2 by muscle cells</div> Explain the advantages of collecting a large number of results. MS [3]<ul><li>Allows anomalies to be identified</li><li>Increases reliability of mean</li><li>Allows use of stats test</li></ul> What is osmoregulation?control of water potential of the blood What 2 functions does the kidney carry out?<ul><li>Ultrafiltration of blood</li><li>Selective reabsorption of useful substances </li></ul> What 3 [   ]s do the kidneys regulate?"<ul><li><font color=""#ff0000"">Water </font>- cells only function in isotonic solution;required for metabolic reactions</li><li><font color=""#ff0000"">Ions </font>- required for cellular processes and osmotic balance</li><li><font color=""#ff0000"">Urea </font>- toxic product of amino acid breakdown so could damage cells</li></ul>" " <div id=""io-header""></div> <div id=""io-wrapper""> <div id=""io-overlay""><img src=""66a1813ca5b3428e823e47802c693e1c-ao-1-Q.svg"" /></div> <div id=""io-original""><img src=""tmpt25epjnl.png"" /></div> </div> <div id=""io-footer""></div> <script> // Prevent original image from loading before mask aFade = 50, qFade = 0; 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} </script> " What happens at the glomerulus / Bowman's Capsule?ultrafiltration What happens at the PCT?"<font color=""#ff0000"">selective </font>reabsorption of glucose/water/ions" What happens at the loop of Henle?"Reabsorption of water/ions for <font color=""#ff0000"">OSMOREGULATION</font>" Recall the constituent parts of the barrier between capillaries and lumen of Bowman's capsule."<ul><li><font color=""#ff0000""><b>Endothelium </b></font>- have narrow gaps so plasma can pass through</li><li><font color=""#ff0000""><b>Basement membrane </b></font>- fine mesh of collagen fibres/glycoproteins which act as a filter</li><li><font color=""#ff0000""><b>Podocytes </b></font>- epithelial cells w/ projections called foot processes. Form gaps. </li></ul><div><br></div><div><img src=""paste-214ffb7a4bdb291f90ba37efb5b7bd8bbeba02cb.jpg""><br></div>" What is red urine indicative of?"<ul><li>Indicates <font color=""#ff0000"">RBCs </font>in the urine</li><li><font color=""#ff0000"">Ultrafiltration </font>not working due to injury / infection - basement membrane is damaged</li><li><font color=""#ff0000"">Proteins </font>will also be in urine</li></ul><div><img src=""paste-429a5b6e48f552a7a0d1e578244dbc186afd3be4.jpg""><br></div>" Recall the process of ultrafiltration. MS [4]"<ul><li><font color=""#ff0000"">High </font>blood/hydrostatic pressure</li><li>Water/glucose/ions/urea pass out</li><li>Through small gaps/<font color=""#ff0000"">fenestrations </font>in capillary endothelium</li><li>Through <font color=""#ff0000"">basement </font>membrane</li></ul>" Recall the process of selective reabsorption that occurs at the PCT. [4]"<ul><li>Na+ <font color=""#ff0000"">Atrans </font>out of cells lining PCT. (ATP needed; mitochondria supply)</li><li>[Na+] lowered; <font color=""#ff0000"">maintaining </font>Na+ conc gradient (lower in the cell than the lumen)</li><li>Na+ diffuse in down conc gradient, <font color=""#ff0000"">co-transporting glucose</font> (or AA, Cl-, other mols..)</li><li>Glucose <font color=""#ff0000"">diffuses </font>from PCT cell into blood </li></ul><div><img src=""paste-1964c427c7eb6d121765129763d511350f6fe968.jpg""><br></div>" How are the PCT cells specialised for reabsorption? [4]"<ul><li>Microvilli <b><font color=""#ff0000"">so </font></b>large SA</li><li>Co-transporter proteins <b><font color=""#ff0000"">for </font></b>transport of AA/Glucose in association with Na+ ions by f.diffusion</li><li>Many channel proteins <b><font color=""#ff0000"">so </font></b>more diffusion</li><li>Many mitochondria <b><font color=""#ff0000"">to </font></b>supply ATP for active transport</li></ul>" By what processes does selectively re-absorption occur at the PCT?<ul><li>Active transport (all AAs, some glucose)</li><li>Facilitated diffusion (some glucose) </li><li>Osmosis (water)</li></ul> Sketch and label the functional unit of the kidney."<img src=""paste-415264d84e3cc97fe297db8efd111ef4001e8c14.jpg"">" Recall how the loop of Henle reabsorbs water. MS [8]"<ul><li>In descending limb sodium(ions) <font color=""#ff0000""><b>diffuse </b></font>in;<br></li><li>Descending limb water moves out / <font color=""#ff0000""><b>permeable </b></font>to water;</li><li>In the ascending limb sodium(ions) <b><font color=""#ff0000"">actively </font></b>transported out;</li><li>Ascending limb walls are too thick and hence is <b><font color=""#ff0000"">impermeable </font></b>to <b><font color=""#ff0000"">water</font></b>;</li><li>Low water potential / high concentration of ions in the medulla / tissue fluid;.  </li><li>The longer the loop / the deeper into medulla, the <font color=""#ff0000""><b>lower the water potential</b></font> in medulla / tissue fluid;</li><li>Water leaves collecting duct / DCT;</li><li>By <font color=""#ff0000""><b>osmosis </b></font>/ down water potential gradient</li></ul><div><img src=""paste-df46757b5c375a7c23492f45e6a9d9526380e034.jpg""><br></div><div><img src=""paste-20b458d2e66fde33d0831028a30ac65dbd47dc30.jpg""><br></div>" "Explain the role of the hypothalamus, posterior pituitary gland and ADH in osmoregulation <font color=""#ff0000"">when there is a decrease in water potential in the blood</font>. ""<ul><li>Detected by <font color=""#ff0000"">osmoreceptors </font>in hypothalamus</li><li>Hypothalamus produces <font color=""#ff0000"">ADH </font></li><li>Posterior pituitary gland secretes more ADH into the blood </li><li>ADH travels in blood to kidney and attaches to receptors on DCT / collecting duct</li><li>ADH incr. water permeability of walls of DCT / collecting duct to water</li><li>By causing vesicles with aquaporins to fuse with CSM;</li><li>More water absorbed from DCT / collecting duct by <b>osmosis</b>.</li><li>(Less water lost to urine) smaller vol, more conc. urine.<br></li></ul>" "Explain the role of the hypothalamus, posterior pituitary gland and ADH in osmoregulation <font color=""#ff0000"">when there is an increase in water potential in the blood.</font> [5]""<ul><li>Detected by <font color=""#ff0000"">osmoreceptors </font>in hypothalamus</li><li>Hypothalamus produces <font color=""#ff0000"">less </font>ADH</li><li>Posterior pituitary gland secretes less ADH into the blood </li><li>Less ADH travels in blood to kidney and less attach to receptors on DCT / collecting duct</li><li>This decrease water permeability of walls of DCT / collecting duct to </li><li>Less water absorbed from DCT / collecting duct by <b>osmosis</b>.</li><li>(More water lost to urine) larger vol, less conc. urine.</li></ul>" How does ADH work?"<ul><li>Binds to <b><font color=""#ff0000"">specific receptor</font>s </b>on collecting duct wall</li><li>Triggers <font color=""#ff0000"">phosphorylase </font>synthesis in cell</li><li>Phosphorylase causicles vesicles w/ <font color=""#ff0000"">aquaporins </font>to fuse with CSM</li><li>Aquaporins are <font color=""#ff0000"">channel proteins</font> that water pass through, increase water permeability</li></ul><div><br></div><div><img src=""paste-079181d12137c628773ef1750ca8b3a7ea4316df.jpg""><br></div>" Explain ways in which the tracheal system is adapted for gaseous exchange. MS [4]<ul><li>Thin tracheole walls so short diffusion distance to cells</li><li>Highly branched tracheoles so short diffusion distance + large SA</li><li>Fluid moves out during exercise; faster diffusion through air</li><li>Body can be moved to move air; maintaing conc gradient. </li></ul> What is the function of tendons in the heart?Prevents <b>inversion </b>of valves due to high pressure

AQA Biology A-Level

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