Biological Molecules: Example of Biological molecules? Carbohydrates, proteins, Lipids, DNA, ATP, Water and inorganic ions What is a monomer? Amino acid is a monomer. What are polymers? Long chain of monomers joined together Building blocks of carbohydrates? Monosaccharides Carbohydrate Structure Carbon, hydrogen +oxygen ● Carbohydrate Functions? ● ● Chemical bond has a lot of energy which makes it a good energy source in plants and animals. Energy Store (starch in plants and glycogen in animals) Structure is soluble making it easy to transport around a cell. What type of sugar is glucose? Hexose (monosaccharide w/6 carbon atoms) 2 types of glucose? Alpha and Beta glucose Condensation between 2 monomers between OH groups releasing water. Forming a glycosidic bond. Reaction which joins monosaccharides? Bond formed when 2 monosaccharides/carbohydrates join? Glycosidic bond forms How do you form a disaccharide? 2 monosaccharides joined together by a glycosidic bond - in condensation reaction. ● Removes a water molecule How is maltose (disaccharides) formed? Alpha Glucose + Alpha Glucose How is Sucrose (disaccharides) formed? Alpha Glucose + Fructose How is Lactose formed? Beta Glucose + Galactose What reaction breaks down polymers? Hydrolysis reaction -- addition of water ● Breaking down into monomers What is the test for testing reducing sugars? Add Benedict's solution (blue) and heat in warm water bath. ● If Reducing sugar then it turns brick red Test for Non-reducing sugars? What are polysaccharides? Examples of polysaccharides? Structure of starch? Heat w/ benedict’s solution - when no change detected carry out: ● Add dilute HCl + heat (breaks glycosidic bond). ● Then sodium hydrogencarbonate (neutralise), then benedict's test -turn brick red 2 or more monosaccharides joined together by condensation Glycosidic bond formed. ● ● ● Long straight chain of 2 Alpha glucose which is coiled. ● Found in only plants ● Feature of Starch? ● What is the test for Starch? Starch - energy stored in plants Glycogen - energy stored in animals Cellulose - cell wall of plants ● ● Insoluble in water so water potential is not affected easily transportable & doesn’t diffuse out of the cell. Coiled so compact = good for storage Add iodine solution. If present then it will turn orange to blue-black. What is Glycogen used for? Main energy storage for animals Structure of Glycogen? ● Polymer of alpha glucose joined by glycosidic bonds Long, highly branched straight chains of alpha glucose Feature of Glycogen? ● ● ● Side branches- quick release of energy for respiration. Very compact molecule so good for storage + Insoluble so doesn't affect water potential Structure of Cellulose? Long, unbranched chain of beta glucose forming Straight chains Features of Cellulose? Straight chains are cross linked by hydrogen bonds forming microfibrils providing strength and rigidity. Types of Lipids? Structure of Triglycerides? How are triglycerides formed? ● ● Triglycerides Phospholipids ● ● 4 molecules overall One molecule glycerol + Fatty acid tails joined by ester bonds Condensation of fatty acid and glycerol molecule. ● Ester bond formed + water released. Difference between Unsaturated and Saturated triglycerides? ● Saturated don't have double bonds between carbon atoms. Unsaturated have at least one double bond. ● 1 Glycerol + 2 Fatty acid and 1 Phosphate group ● Phosphate group is hydrophilic (head attracts water) Fatty acid tails (hydrophobic) so forms a barrier to prevent water soluble molecules to pass through membrane. This forms phospholipid bilayer ● What is Phospholipids structure? ● Feature of Phospholipids? ● Long hydrocarbon tail containing lot of chemical energy -energy released when they're broken. Structure linked to functions of Lipids? Also insoluble as tail is hydrophobic so doesn't affect water potential. Uses for lipids? -Water proofing -Storage -Membranes -Energy store -Energy Source What is the test for lipids? Emulsion test: 1.Shake substance w/ethanol + add water 2.Should show as a milky emulsion Importance of water molecules to organisms? 1. Strong Cohesion: Water has hydrogen bonds. When water freezes it becomes ice and floats due to hydrogen bonds. 2. High Specific Heat Capacity: Lots of energy required to separate water molecules due to hydrogen bonds. 3. Metabolite: B reaks down molecules by hydrolysis ; used in photosynthesis; condensation reactions. Also an important solvent 4. Large latent heat of evaporation- cooling effect through evaporation. What are the base of proteins? Amino acids are the monomers How are dipeptides formed? 2 amino acids join together by condensation What are polypeptides? ● Many amino acids join together. By condensation What are proteins made up of? Contains 1 or more polypeptides What do amino acids contain? There are 20 different amino acids and they all differ in the R variable group. Amino acids are linked by condensation reactions. Water is released. Forms peptide bonds. How are peptide bonds formed between amino acids? What is the primary structure of proteins ? Sequence of amino acids. ● Polypeptide chain held by peptide bonds What is the secondary structure of proteins ? ● ● Primary structure coils into alpha helix Held together by hydrogen bonds What is the tertiary structure? ● ● ● Coiled further. 3D structure Held together by disulfide/hydrogen/ionic bonds What is the Quaternary structure? Types of proteins are there? Made up of more than 1 polypeptide chain ● ● globular (haemoglobin) fibrous Function of proteins? EATS ● ● ● ● How do enzymes break down large molecules? The substrate binds to the enzyme (active site,complementary) , forming a enzyme-substrate complex. -By condensation (removing water) -The binding of the substrate and enzyme places stress on the bonds (hydrogen) -then the molecules separate. What is the test for proteins? Biuret test: ● Add sodium hydroxide solution ● Then Copper (II) Sulfate (should turn purple if Protein present) ● if proteins not present then it stays blue. Enzymes break down food molecules Antibodies (in immune systems) Transport proteins (in cell membranes) Structural proteins ● What are enzymes? ● Biological catalysts which provide an alternate pathway and lowers activation energy. ● Lock Key theory- active site is rigid. Substrate must be exactly complementary to form ES complexes. Induced-Fit - active site changes shape slightly, substrate binds with active site to form E-S complexes. Compare lock and key with induced fit? ● What makes enzymes specific? ● ● Has a specific active site shape. Only complementary substrates can be binded w/ a ctive site to form Enzyme substrate complex. What is active site of the enzyme determined by? ● ● Tertiary structure If substrate different then cannot form ES complex. 1. 2. 3. 4. As temp increases, kinetic energy increases More successful collisions as molecules are faster More E-S formed increased rate of reaction (until optimum) After optimum bonds in tertiary structure breaks (hydrogen, disulfide, ionic) Active site changes shape; so no longer complementary ES complex cannot be formed Enzyme denature 5. Effect of temperature on enzyme activity? 6. 7. 8. ● Effect of pH on enzyme activity? ● ● ● ● Effect of substrate concentration on enzyme activity? ● ● What are competitive inhibitors? What are non-competitive inhibitors? Increase in substrate, increases the chance of successful collisions More Enzyme Substrate Complexes formed ; increase R.O.R Continues until the enzyme's active sites are saturated/ full= maximum rate of reaction ● ● ● ● Increase in enzyme concentration, increases the chance of successful collision Forms E-S complex Increase rate of reaction. Continues until all substrates have been used up. Then R.O.R decreases. ● ● ● ● Molecules with same shape to substrate molecules Complementary shape to active site Binds to active site, blocking the active site. Preventing ES complex to be formed. ● ● Binds to enzyme away from active site Causes active site to change shape (no more complementary) Less ES complex formed as tertiary structure has changed. Increasing concentration doesn’t make a difference. ● Effect of enzyme concentration on enzyme activity? If pH away from optimum, bonds in tertiary structure break Active site changes shape No longer forms ES complexes Enzyme denature ● ● Nucleic Acids What are DNA and RNA? What do DNA and RNA do? Function of DNA? Function of RNA? What are ribosomes made up of? Nucleic acids ● ● Carry information Made of proteins ● Deoxyribonucleic acid- used to store genetic information. ● Ribonucleic acid- main function is to transfer genetic information from DNA to ribosomes to make proteins ● RNA and Amino acids ● ● ● Deoxyribose sugar Phosphate group Nitrogen containing one of the organic bases; Adenine, cytosine, guanine or thymine ● ● ● Ribose sugar Phosphate group Nitrogen containing one of the organic bases ; adenine, uracil, Cytosine, Guanine Building block of DNA? Building block of RNA? RNA molecule is a relatively short polynucleotide chain. ● How does a dinucleotide form? ● How are polynucleotides formed? How is the Double helix of DNA formed? Many mononucleotides joined together in condensation ● ● 1. 2. Structure/Properties of DNA? 3. 4. 5. How do organic bases help stabilise DNA? ** What does Semi-conservative replication allow? What does semi-conservative replication do? Condensation reaction between the phosphate group of one nucleotide and another sugar. Joined together by phosphodiester bond ● When 2 polynucleotide chains are held together by hydrogen bonds Between complementary base pairs 2 nucleotide chain joined by hydrogen bonds; allowing for molecules to unzip to replicate easily; hydrogen bonds make it more stable Complementary base pairing; allowing for a ccurate replication between 2 polynucleotides. A-T, C-G pairing means equal amounts of bonding Polynucleotide can twist to form DNA double helix; makes it more stable as less damaged caused. Also more compact Long & twisted so store lots of information ● Hydrogen bonds between base pairs holds 2 strands together. Many hydrogen bonds formed increasing the strength. ● Genetic continuity between generations of cells Half of original DNA is built onto a new DNA strand. What is the process of semiconservative replication of DNA? 1. DNA helicase breaks the hydrogen bonds between the complementary bases in the polynucleotide strands 2. Double helix unwinds; 2 strands formed 3. Free complementary nucleotides bind t o the exposed bases on the template strand. 4. DNA polymerase joins nucleotides to form a strand What is ATP? ● ● Adenosine Triphosphate Source of energy in a cell during respiration ● ● Glucose converts its energy to produce ATP. ATP then releases in small quantities of energy for e.g. Respiration How is energy produced from ATP using glucose? Ribose sugar; 3 phosphate groups; adenine group What is the structure of ATP? What is the synthesis of ATP? What can the inorganic phosphate be used for which is produced during synthesis of ATP? What is the re-synthesis of ADP and Pi? What is the biological importance/ Uses of ATP? What is the uses of ATP in organisms? ● ATP is broken down/hydrolysed into ADP; ● This is a hydrolysis reaction (adding water) ● An inorganic phosphate is catalysed by ATP hydrolase. ATP + H20 --> ADP + Pi + Energy ● ● ● ● Pi released can be used for phosphorylation of other compounds This makes them more reactive. Condensation reaction of ADP and Pi. This reaction is catalysed by enzyme ATP synthase during photosynthesis and respiration. Remember RIPS ● ReSynthesized rapidly in cells ● Immediate source of energy; as only one bond required to break. Also, provides a lot of energy. ● Phosphorylation of other compounds making them more reactive ● Small, manageable amounts of energy released. ● ● ● ● Maintain body temp Cell division Protein synthesis DNA replication Section 2: Cells How to measure the diameter of organelles using microscope? ● ● ● Measure with eyepiece graticule Calibrate with stage micrometer Repeat and calculate means What is Magnification? Shows how much bigger an image appears than the specimen. What is resolution? Shows the clarity of the image; -Also determines by how well a microscope distinguishes between 2 points which are close together. What is formula for magnification? magnification = image size/ actual size 1 mm=1,000 micrometre = 1,000,000nm What is an optical microscope? ● ● Uses light to shine through sample. Used to measure the size of an object Advantage of Optical microscopes? ● ● ● Inexpensive Portable Minimum training required Drawbacks of Optical microscopes? ● ● Low magnification + resolution Specimen have to be stained ● Uses electromagnets to transmit electron beams through a sample Denser parts of the specimen absorb more electrons and appear darker What is a Transmission electron microscope (TEM) ? What is the advantage of TEM? Limitations of TEM? What is scanning electron microscope? Advantage of SEM? Disadvantage of SEM? ● ● TEM has the highest resolution and magnification of all microscopes. ● ● ● ● ● Expensive and Large Specimen has to be dead Specimen has to be in a vacuum Staining is required to see specimen. Specimen has to be thin ● Fires a beam of electrons at a specimen. ○ The electrons are knocked off any surface it hits ● ● Produces a 3D image Magnification and resolution is better than optical microscope. ● ● ● Specimen must be dead Must be in a vacuum It is large and expensive Used to separate organelles from different cells What are the 3 main steps of cell fractionation? 1.Homogenisation 2.Filtration 3.Ultracentrifugation What is the process of homogenization? What conditions are required for cell fractionation? ● ● Vibrate the cells This process breaks plasma membranes and releases organelles into solution. ● ● Solution must be cold; to reduce enzyme activity Isotonic (same water potential); prevent organelles to burst or shrink. Buffered; maintain a pH ● Why is isotonic important? What is the step of ultracentrifugation? ● ● ● Maintains the same water potential No movement of water by osmosis So allows cells to not change shape ● Cell fragments put in a t est tube and spun in a centrifuge at a low speed Heaviest organelles go to the bottom and form a layer of sediment Fluid at t op removed and spun at faster speeds to separate lighter organelles. ● ● Eukaryotic cell structure in animals: What is the function of the nucleus? What is the function of cell-surface membrane? Nucleus controls the cell's activity ● Contains genetic material to make e.g. proteins ● Contains chromosomes ● Makes RNA and Ribosomes ● Contains linear DNA ● ● Made up of proteins and lipids It allows the movement of substances into and out of cells ● ● ● Oval shaped Folded membrane forms Crista Matrix contains DNA, ribosomes, proteins and lipids ● ● Site of Aerobic respiration; ATP is produced. Found in cells which require a lot of energy ● Surface covered with ribosomes ● Modifies and transports proteins which are made by ribosomes ● Has no ribosomes What is the structure of Mitochondria? What is the function of Mitochondria? What is the structure of Rough Endoplasmic Reticulum? Function of Rough ER? Structure of Smooth ER? Function of Smooth ER? ● Synthesis and p rocesses lipids + carbohydrates Structure of ribosomes? ● ● There are 2 types of ribosomes; 80S & 70S 80S in eukaryotic and 70S in prokaryotic Function of Ribosomes? ● Site of Protein synthesis Structure of Golgi Apparatus? ● Vesicles can often seen on the edges. Function of Golgi Apparatus? ● ● ● Processes and packages new l ipids and p roteins Makes lysosomes. Forms vesicles What are lysosomes? Associated with tissue break down Eukaryotic cell structure in Plants: Structure of Chloroplasts? ● ● Only found in plant cells Double membrane Function of chloroplasts? ● Site of Photosynthesis Structure of Vacuole? ● Fluid filled sac Function of Vacuole? ● ● Only found in plants Fluid contains water Structure of cellulose cell wall? ● ● Rigid structure which surrounds the cells in plants. Made of c ellulose Function of cellulose? ● Supports cells and prevents them from changing shape What are tissues? Group of eukaryotic cells working together to perform a particular function; e.g. Epithelial tissue How are Organs formed? ● Different tissues working together to form organs; different organs make up organ system. ● Prokaryotic cell structure: What are Prokaryotic cells? Type of organisms e.g. bacteria; doesn't have nucleus. ● ● ● What are the differences between Eukaryotic and Prokaryotic cells? ● ● ● ● Prokaryotic cells are much smaller than Eukaryotic cells E cells have c ell walls In P cells they have circular DNA molecules called plasmids Cytoplasm which doesn't contain membrane-bound organelles e.g mitochondria. Smaller ribosomes in P cells- 70s Cell wall made of murein; a glycoprotein. whereas animals only have membranes and plants have cellulose P cells have flagella What do many prokaryotic cells have? ● ● ● One or more Plasmids (loops of DNA) Capsule surrounding cell One or more flagella. How do prokaryotic cells divide? Process of binary fission: 1. Circular DNA and plasmids replicate 2. Division of cytoplasm produces 2 daughter cells, each with 1 copy of circular DNA. 3. Forms 2 identical daughter cells. What is a virus? Acellular; not a cell as they are non living. ● Viruses invade and reproduce inside cells of other organisms. -Contains genetic material -Attachment protein; allowing them to stick onto a host cell -Capsid around the core. What is the structure of a virus? How do viruses replicate themselves? ● ● ● ● They are acellular so cannot divide + require host cell They attach onto host plasma membrane Inject DNA or RNA into host cell Infected host cell replicates the virus particles. ● Cell cycle when Eukaryotic cell divides to produce 2 (identical) daughter cells, each with identical copies of DNA. ● ● ● Growth, Asexual reproduction Tissue repair. What is mitosis? What is Mitosis needed for? Remember IPMAT : Interphase, Prophase, Metaphase, Anaphase, Telophase. What is the process of Mitosis? What occurs in Interphase? ● ● DNA unravels and replicates in the nucleus. Organelles also replicate. ● Stays the same as 2 daughter cells formed. Process of mitosis? What happens to the number of chromosomes in mitosis? What is the role of spindle? What is cancer? How does an uncontrolled cell division occur? 1. Attaches to the centromere of chromosome 2. Causes separation of the chromosomes Uncontrolled, rapid cell division leading to formation of tumors and cancer. ● Mutation What are some cancer treatments? -Surgery = aim to remove tumor -Chemotherapy = Using drugs to prevent dividing cancer cells - Treatment given as regular doses to allow time for normal healthy cells to recover in number -Radiotherapy = Radiation used to destroy cancer cells Transport across cell membranes What do cell membranes do? What are cell membranes composed of? They act as a barrier between the cell and the environment; controlling which substances enter and leave the cell. Lipids, proteins + carbohydrates Several different components and these membrane constituents are constantly moving. Components; Phospholipids, Cholesterol, Proteins, Glycoproteins, Glycolipids (receptors) What does the fluid mosaic include? What is the feature of cholesterol? Restricts movement of other molecules moving up the membrane. -Maintains the shape -Provides more rigidity ● What is the process of simple diffusion? What type of process is diffusion? What is simple diffusion determined by? ● ● Movement of molecules from area of high concentration to lower concentration; Until it reaches dynamic equilibrium (evenly distributed) Down the concentration gradient Passive process meaning no energy is required ● ● ● ● Surface area (e.g. folding) Thickness of membrane Concentration gradient Temperature (more ke = more movement) How does large surface area allow for fast rate of diffusion? ● Larger area for molecules/particles to diffuse into cell -Oxygen What does simple diffusion let through -Carbon Dioxide the membrane? -Fat-soluble vitamins What is Facilitated diffusion? Faster than simple diffusion ● Used to transport large and polar molecules. e.g. fructose, glucose. ● Uses channel proteins & carrier proteins ● How do carrier proteins work in facilitated diffusion? ● ● Large molecules binds with carrier protein - on cell surface Protein changes shape allowing the molecule to be transported through the cell Molecule detaches from transporter protein and protein reverts to original shape What is the process of osmosis? Diffusion of water molecules from an area of high water potential to an area of low water potential. -Through a partially permeable membrane. What has the highest water potential and what does this mean? Pure water- meaning water will diffuse from the water molecules into an area with lower water potential. What occurs when plant cell is surrounded by pure water? What is the process of active transport? Process of active transport? Describe the process of cotransport of glucose? ● ● ● ● Swells but no burst Cell wall prevents it from bursting Made of cellulose- strong material Cell is turgid Movement of molecules and ions from low to high concentration; ● Using energy ● Against the concentration gradient; ● Uses carrier protein Molecules bind to carrier protein ATP is hydrolysed into ADP & Pi & energy Pi and energy causes carrier proteins to change shape. Carrier protein releases the molecules to the other side of the membrane (high conc) 5. Carrier protein releases the Pi to revert to original shape. 1. 2. 3. 4. 1. Glucose moves in with sodium (into epithelial cells); 2. Via channel protein 3. Sodium removed (from epithelial cells) by active transport 4. Into blood; 5. Maintaining low concentration of sodium (in epithelial cell) / maintaining sodium concentration gradient (between lumen and epithelial cells); 6. Glucose moves into blood; 7. By (facilitated) diffusion; The epithelial cells that line the small intestine are adapted for the absorption of glucose. Explain how? Cell recognition and Immune system What are pathogens? How do pathogens cause disease? How do foreign cells get recognised? What is a phagocyte? What is the process of Phagocytosis?** ● Disease causing microorganisms e.g. bacteria. virus, fungi ● ● Produce toxins Damage self cells ● Every molecule has a specific molecule on its surface that identifies it. ● White blood cell which ingests and destroys pathogens by a process called phagocytosis. Found in blood and tissues; are the first cells to respond to an immune system ● ● What is an antigen?** ● Protein on the surface of pathogens which stimulate an immune response. Causing antibody production/ immune response What is antigenic variability and how does it affect disease prevention? ** ● ● Antigen alters shape So no antibodies formed What are the roles of antigen-presenting cells during cell mediated response? ● Phagocytes present antigens onto its surface for T cells to bind together. What is the role of T- lymphocytes in cell mediated immunity? T cells complementary bind onto the antigen on the phagocyte's surface; ● When binded, this activates other T cells to divide rapidly by mitosis and form genetic clone T cells. ● What can cloned T-helper cells do? ● ● Activate cytotoxic T cells which kill abnormal and foreign cells. T-helper cells stimulate the production of B cells to produce antibodies Stimulate phagocytosis in phagocytes 1.Each B cell have a different shaped antibody which means it can bind with different types of antigens 2.When antibody on the surface of B cell is complementary to an antigen- they bind together. What is the process of Clonal selection 3.When binded this activates B-cells to rapidly divide into inc. B cells? plasma cells. 4.The plasma cells mainly produces antibodies which are complementary to the antigens and; produces memory cells. Why are producing memory cells important? ** What is an antibody? ● Proteins with specific binding sites to the antigen. ● ● ● Has 4 polypeptide chains so has a quaternary structure Variable region where specific antigens can fit onto it. Hinge region; allowing flexibility and binding to multiple antigens. ● Antibody has 2 binding sites so can bind 2 pathogens at the same time. Foms Antigen-Antibody complex causing clumps of pathogens to form. Phagocyte binds to antibodies and digests the pathogens at once. Structure of antibody? Why can antibody only recognise 1 antigen? ** Process of Agglutination? ● ● Explain how antibodies were produced when the mice were injected with sheep red blood cells?** What is the primary immune response? What are plasma cells? ● ● ● ● ● T cell attaches to antigen of pathogen T cell activates immune system; T cell divides & produces T helper cells T helper cells trigger B cells to produce antibodies B cells divides producing plasma cells making antibodies + memory cells ● ● Identical to B cells. Form antigen-antibody complex with pathogens. ● What occurs during secondary immune response? ● ● If same pathogen enters the body; immune system will respond faster. Clonal selection occurs faster. Memory B cells are activated and divides into plasma cells to produce correct antibody. Memory T cells are activated and divide into correct T cells to k ill cells carrying antigen. What are vaccines? Ethical issues of vaccines? -Use of animals -Pathogen might still be active -Antigenic variation may occur -Religious obligations Vaccines protect people against disease. Explain how. Describe how giving vaccine leads to production of antibody? What is active immunity? Production of antibodies by individuals own immune system eg. natural after disease ● artificial (after vaccination) What is passive immunity ? ● Introduction of antibodies from an outside source -eg. from mother through breastfeeding or placenta -artificial (injection) ● What are the differences between active and passive immunity? Human Immunodeficiency Virus which causes AIDS What is the structure of HIV? Process of HIV replication in T cells? 1. HIV attaches onto receptor molecules on host T helper cell 2. Capsid released into cell, where it uncoated and releases genetic material (RNA) into the cell's cytoplasm 3. Reverse transcriptase converts viruses RNA to DNA 4. Viral DNA is integrated into h ost DNA 5. New RNA is made and virus is released. How does HIV cause the symptoms of AIDS? -HIV remains suspended at low levels for many years -Aids then develops after many years. -Aids progresses to decrease the number of immune system cells further and symptoms become serious. -During late stages; patients can develop serious infections. ● What are monoclonal antibodies? ● One type of antibody complementary to one type of antigen Made same plasma cells. Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why? What are the uses of monoclonal antibodies? -Medical diagnosis; -Allows for attaching an antigen to an antibody to recognise a disease Ethical issues of monoclonal antibodies? -expensive -side effects -Mice dies after testing How do antibiotics work? Why are antibiotics ineffective against viruses? ● ● They disrupt cell wall Stops DNA replication ● ● Antibiotics only target bacterial enzymes Viruses don't have their own enzymes and ribosomes so cannot be inhibited Virus don't have a cell wall ● What is the ELISA test? -Allows you to see if a patient has antibodies to a certain antigen. e.g. pathogenic infections How is the ELISA test used? 1. Antibody used which has an enzyme attached. 2. Enzyme can react with a substrate to produce a colured product. 3. if colour change is present then the certain antigen or antibody is present. Section 3: Organisms exchange with their environment ● ● They have a large surface area to volume ratio Thin surface (short diffusion distance) Why can’t Animals/ Plants perform exchange via surface ? ● ● ● ● Small surface area to vol ratio Long diffusion distance Impermeable surface to prevent pathogens entering Decrease water loss Surface area:Vol ratio compared to large and small organism? ● ● Small organisms have a large SA:Vol ratio Large organisms have a small SA: Vol ratio Features for good exchange? ● ● ● Large surface area Thin surface Large concentration gradient (faster diffusion) ● Gills made up of gill filaments + gill lamellae (providing large surface area for gas exchange). Lamellae + filaments have a thin epithelium for fast rate of diffusion + short diffusion distance & are permeable. Why can single cell organisms (microorganism) exchange directly via surface? Structure of gills in fish? ● ● ● ● What is the countercurrent flow in fish? ● ● Blood and water flow in opposite directions. Maintains a large concentration gradient between water and blood. Conc. of oxygen in water is always higher so O2 diffuses into blood of fish. Along the length of the gill This increases the O2 conc in blood of the fish. ● ● ● ● ● ● Structure of tracheal system in insects? Adapted features of insects to prevent water loss? ● ● ● How is gas exchanged in plants? How does stomata prevent/allow gas exchange? Controlling water loss in plants? ● Waterproof, waxy cuticle all over body and exoskeleton to prevent water loss by evaporation. Spiracles open & close. Main site is mesophyll cells.They have large surface area so can absorb light. Gas can move in and out through stomata. ○ These are found on the epidermis of leaf ● ● They open and close to reduce water loss. Guard cells control opening and clmosing of the stomata ● ● Water enters making cells turgid. If cell begins to lose water; then becomes flaccid and closes the pores. Stomata close at night to prevent water loss ● ● ● Adaptations of Xerophytic plants? O2 moves into through spiracles and connects to the trachea. Down conc. Gradient Trachea connect to tracheoles which are thin Tracheoles attach directly to respiring tissues (deliver O2 and remove CO2) CO2 moves down its concentration gradient towards the spiracles. Insects use rhythmic abdominal movements to move air in and out. ● ● ● waxy cuticles reduced surface area to volume ratio for reduced water loss through transpiration layers of hair reduced no. of stomata closing stomata when water availability is low Structure of human gas exchange? Human gas exchange occurs in the lungs. 1. Air enters through the trachea 2. Trachea splits into 2 bronchi 3. Each bronchus branch into smaller bronchioles 4. Bronchioles end in air sacs called alveoli Trachea -> Bronchi -> Bronchus -> Bronchioles -> alveoli ● Key features of the gas exchange system? ● ● ● ● What type of process is breathing? Trachea/Bronchi supported by rings of cartilage for support ○ Cartilage is C shaped for flexibility and prevent collapse Bronchioles wall are made from smooth muscle Alveoli are one cell thick so ; short d.d and fast d/ pathway Ventilation means constant blood supply by capillaries so steep conc. gradient maintained. large no.of alveoli so large surface area -active process (using energy) Stages of inhalation? 1. 2. 3. 4. 5. 6. External intercostal muscles contract Ribs moves upwards and outwards Diaphragm contract causing it to fatten Volume in chest Increases Pressure in chest lower than atmospheric pressure Air moves into lungs Stages of exhalation? 1. External intercostal muscles relax ; internal intercostal muscles contract 2. Diaphragm relaxes (Dome shape) and moves upwards 3. Volume of chest cavity decreases 4. Pressure greater than atmospheric pressure 5. So air moves out of lungs Pv (pulmonary ventilation) = tidal volume x breathing rate Formula for pulmonary ventilation? Exchange of gases in lungs -tidal volume = volume of air breathed in/out in one breath -breathing rate = number of breaths per minute -Pulmonary Ventilation = volume of air breathed in/out per minute -large no.of alveoli and are folded in lungs so large SA for exchange ● -O2 diffuses out of alveoli through the alveolar epithelium ● Risk factors for lung disease? What is digestion? How are carbohydrates digested? How is lipid digested? -smoking -air pollution -infections -occupations ● Hydrolysis of large molecules into smaller molecules which can be absorbed across cell membranes 1. 2. 3. 4. Amylase converts (Starch) to maltose: Maltase; Maltose to glucose; Hydrolysis Of glycosidic bond ● Lipase breaks lipids into monoglycerides and 2 fatty acids Lipase produced in pancreas + released in small intestine Bile salts produced in liver emulsify lipids into small droplets called micelles ● ● How is protein digested? What is the structure of ileum? Proteins are broken down by peptidases: ● Endopeptidases hydrolyse the internal peptide bonds. Found in stomach ● Exopeptidases; hydrolyse at the end of the protein producing dipeptides. Found in small intestine ● Dipeptidases; membrane bound and hydrolyse peptide bonds between dipeptides into single amino acids ● ● ● ● Describe the process of cotransport of glucose? And through capillary endothelium and into haemoglobin in blood by diffusion. Thin walls (reduced/ distance) Villi and microvilli increase surface area for diffusion Muscles move food along the ileum to maintain diffusion gradient Well supplied with blood vessels. 8. Glucose moves in with sodium (into epithelial cell); 9. Via channel protein 10. Sodium removed (from epithelial cell) by active transport 11. Into blood; 12. Maintaining low concentration of sodium (in epithelial cell) / maintaining sodium concentration gradient (between lumen and epithelial cell); 13. Glucose moves into blood; 14. By (facilitated) diffusion; Mass transport What is structure of haemoglobin? Protein with a quaternary structure ● Contains haem group allowing oxygen to be binded Role of haemoglobin in transport of oxygen? Explain how oxygen is loaded, transported and unloaded in the blood. ** ● ● ● Transport oxygen haemoglobin + oxygen <==> oxyhaemoglobin Oxygen can bind reversibly allowing it to be loaded in the lungs and unloaded in respiring body tissues. 1. Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin; 2. Loading / uptake / association in lungs; 3. at high pO2; 4. Unloads / dissociates / releases to respiring cells / tissues; 5. at low pO2; 6. Unloading linked to higher carbon dioxide (concentration); ● ● ● Each molecule of haemoglobin can carry up to four oxygen molecules Can change shape for further oxygen binding to be easy Haemoglobin has High Affinity in the lungs – due to high partial pressure of oxygen and low partial pressure of carbon dioxide, so haemoglobin loads/associates oxygen in the lungs and becomes saturated (full) What is meant when haemoglobin has a high affinity for oxygen? ● What is the effect of carbon dioxide concentration on the dissociation of oxyhaemoglobin? (Bohr effect) Why does foetal haemoglobin have a slightly higher affinity for oxygen than adult hemoglobin? ● ● Greater conc. of carbon dioxide; the more readily it releases its oxygen. When cells respire, they produce carbon dioxide raising pCO2. This increases the rate of oxygen unloading + dissociation curve shifts to the right So it insures foetus can get oxygen from maternal group through the placenta. Important: ● Curve to the left ● So greater association due to low partial pressure of oxygen in the placenta. Has a high affinity, curve to the left, therefore it can readily Affinity of Organisms in a Low Oxygen associate oxygen at the low oxygen partial pressures Environment? Affinity of active organisms ? Low affinity, curve to the right; -So more oxygen can be unloaded to meet to cell's demand for more respiration ● Affinity of small organisms? ● ● Low affinity due to large surface area to vol ratio; curve moves to the right. Therefore greater heat loss & respiration needs to occur to generate heat. So unloads enough oxygen for cells demand of oxygen What is the advantage of oxygen dissociation curve shifting to the right during vigorous exercise? Allows them to survive in particular environments Why do organisms have different types -Organisms which live in an area of low oxygen have haemoglobin of haemoglobin? with high affinity of oxygen Circulatory system in mammals? What is the structure of the heart? What is coronary artery? Supplies blood to the heart What is the aorta? Connected to left atrium and carries oxygenated blood to all parts of the body. What is the vena cava? Connected to right atrium and carries deoxygenated blood back from the tissues of the body. What is the pulmonary artery? Connected to the right ventricle and c arries deoxygenated blood to the lungs where CO2 is removed and oxygen is replenished. What is the pulmonary vein ? Brings oxygenated blood back from the lungs What does the left ventricle allow?** Has a thick, muscular wall which can contract and pump the blood around the body; ● w/ high blood pressure around the body What does the left atrioventricular valves do? Stops the blood from flowing backwards into the atrium when ventricles contract What does the semilunar valves do? Links ventricles to pulmonary artery ● Prevents backflow of blood into the heart What happens in the process of diastole (relaxation of the heart)? 1. Blood enters atria, increasing the pressure. ● Causing pressure to be higher in atria than ventricles 2. Blood starts moving from atria into the ventricles by the atrioventricular valves. What happens in the process of atrial systole? (contraction) 1.Atria contract causing a greater decrease in volume; so further pressure increase. 2.Remaining blood is forced from atria into the ventricles. What happens in the process of Ventricular systole (contraction of ventricles)? 1.Ventricle volume decreases; so pressure increases causing the ventricles to contract 2.Atrioventricular valves are forced shut 3.Semilunar valve are forced open as blood enters the arteries 4.Pressure begins to decrease in ventricles causing Semilunar valves to shut preventing reverse blood flow How is a heartbeat initiated and coordinated? ** Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta. Formula for Cardiac Output? CO = Stroke Volume x Heart Rate ● stroke volume = volume of blood pumped out of the heart in one beat ● heart rate = number of beats per minute ● Cardiac Output = volume of blood pumped out of the heart in one minute How does blood travel from heart to rest of body? Artery → Arterioles → Capillary → Vein ● What is the structure of arteries? ● Walls are thick and muscular. Also has elastic tissue to stretch and recoil as the heart beat which helps maintain high pressure Endothelium is folded also allowing it to stretch. Means it maintains a high pressure What is the function of arteries? ● ● Maintain high pressure of the blood Muscle withstand pumping of heart What is the structure of arterioles? ● ● Thicker muscle layer than arteries to allow blood flow Thinner elastic tissue as blood pressure is lower What is the function of arterioles? ● Deliver blood from arteries to the capillaries What is the structure of capillaries? What is the function of capillaries? ● Smallest blood vessel -Narrow diameter ; 1 cell thick ● ● Delivers nutrients to the body tissues Removing the waste products of metabolism ● ● ● ● Wide lumen Layers of collagen, smooth muscle Contains one-way flow valves Less elastic tissue as there is little pressure Advantages of capillaries being narrow? Structure of veins? Functions of veins? Transports deoxygenated blood back to the heart at low pressures ● What is the process of tissue fluid formation? Valves prevent low pressure blood from flowing in the wrong direction. 1. At the arteriole end of the capillary, there is a high hydrostatic pressure which forces water and solutes out in blood plasma through the thin capillary wall. 2. Large proteins remain in capillary. 3. Tissue fluid contains n utrients and oxygen surrounds body cells. 4. At the venule end of the capillary there is a high oncotic pressure in the tissue fluid which means some solutes drain back into the capillaries. 5. There is are proteins in the capillary so lowers water potential 6. Hence, water moves back into capillary by osmosis. 7. Rest of tissue fluid drains into the lymphatic system. Why does high blood pressure causes Increased Hydrostatic pressure, so more tissue fluid is accumulation of formed; tissue fluid? Not as much can be returned to the circulatory system. Adaptations of Xerophytic plants? Transports water and mineral from the roots up to the leaves in the xylem tissue What occurs in the Xylem in plants? What is the structure of the xylem? How does water move up the stem through the xylem? (transpiration pull)** Why does the diameter of trunk decrease during midday? What are the factors affecting rate of transpiration? What does an increased humidity in air cause? What is the structure of phloem? ● ● ● ● ● Tubes with no end walls Continuous water flow No cytoplasm Allows easy flow of water Lignin for support 1. water evaporates / transpires from leaves; 2. reduces water potential in cell 3. water is drawn out of xylem; 4. Transpiration creates tension 5. cohesive forces between water molecules; 6. water pulled up as a column; Diameter of trunk minimal at warmest Stomata open in light → more water loss; Water evaporates more when warm Hydrogen-bonding between water molecules / cohesion ( / described) between water molecules; 5. Adhesion (described) between water molecules and walls of xylem vessels; 6. (Xylem) pulled inwards by faster flow of water / pulled in by tension; 1. 2. 3. 4. 1.Light Intensity: Greater light intensity; faster the rate 2.Temperature: High temp; faster rate as molecules have more energy SO faster transpiration / by evaporation 3.Humidity: Lower humidity faster rate 4.Wind: Greater wind faster rate; more water molecules blows away 1. 2. 3. 4. 5. Increased humidity leads to decreased transpiration; High humidity means more water in the air increased water potential; reduced diffusion gradient / water potential gradient; Slower rate of water loss / less evaporation; Sieve tube elements; no nucleus; elongated tubes Companion cells; contains nucleus; mitochondria for ATP production What is the mechanism of translocation? 1. At source sucrose is actively (transported) into the phloem 2. By companion cells; 3. Lowers water potential in phloem and water enters by osmosis; 4. (Produces) high (hydrostatic) pressure; 5. Mass flow/transport towards sink/roots/storage tissue; 6. At sink/roots sugars are removed/unloaded; Section 4: Genetic information, variation and relationships between organisms What is a Gene?** How does a Gene/Exon code for a Protein? What is meant by degenerate genetic code? ** What is meant by a codon? ** ● Length of DNA which codes for a single polypeptide. ● Gene is a sequence of triplets. ● Made out of intron and exon -intron = n on-coding DNA (function e.g. turns gene on or off) -exon = coding DNA (codes for protein) -made out of a sequence of bases -each 3 bases code for 1 amino acid (called triplet code) ● Therefore, sequence of bases determines sequence of triplet codes which determine the sequence of AAs = polypeptide chain/primary structure (folds to secondary, then to tertiary/quaternary) An amino acid (Gly) coded by more than one triplet/codon ● ● 3 bases on mRNA That code for a protein Why are stop codons required? ** To stop translation Hence, ribosome detatches to polypeptide What is meant by locus of DNA? ● Position where a gene occupies on a DNA molecule. How does a mutation / change in DNA sequence lead to a non-functional enzyme? ** -change in base sequence -change in sequence of AAs -change in primary structure -change in hydrogen/ionic/disulfide bonds -change in tertiary structure (3D shape) -change in active site shape -substrate no longer complementary -can no longer form enzyme-substrate complex How is a protein assembled? -By transcription and translation -transcription = production of a single stranded complementary copy of a gene (called mRNA) -translation = use sequence of codons on mRNA to assemble protein (tRNA brings in AAs) DNA vs RNA? -deoxyribose sugar vs ribose sugar -thymine vs uracil -double stranded (DNA) vs single stranded -one type vs two types (mRNA and tRNA) ● ● ● What is mRNA? ● ● ● messenger RNA single stranded complementary copy of a gene carries the code for assembling protein (on DNA called triplet code, on mRNA called codon) Linear No base pairing No hydrogen bonds Differences between DNA and mRNA? ● ● What is tRNA? ● ● ● ● transfer RNA single stranded RNA folded over into a 'clover leaf' shape (held by hydrogen bonds between the bases) has an AA attachment site on the top has 3 specific bases on the bottom (anticodon) anticodon binds to complementary codons on mRNA Contains hydrogen bonds Difference between mRNA and tRNA? What is Transcription? Difference between pre-mRNA and mRNA? Transcription is the process of producing a single stranded copy of a gene (called mRNA) ● DNA Helicase breaks the hydrogen bonds between complementary bases in the gene ● The double strand of the gene unwinds ● leaves 2 separate strands (1 coding strand and 1 template strand) ● Complementary RNA nucleotides bind to exposed bases on the template strand ● RNA Polymerase joins the nucleotides together to form mRNA ● Forms pre-mRNA (contains introns and exons) ● The copies of the introns are removed by splicing ● leaves mRNA ● pre-mRNA contains exons mRNA contains only introns ● ● Change in the s equence of chromosomes May cause a change in amino acid s equence in the encoded polypeptide What is Translation? ** What is Mutation? What is a Gene Mutation? A change in the base sequence of DNA ● 2 types of mutation substitution and insertion/deletion ● Substitution; replace one b ase for another (could change structure of protein OR remain same OR may code for stop codon so no protein formed) ● Substitution alters only one codon which maybe a degenerate ● Insertion; adding a base, deletion; removing a base both insertion/deletion causes frameshift, all the triplet codes after the mutation changes, so normal polypeptide chain/protein not produced. What causes mutation? Random or due to mutagens (e.g. chemicals, radiation) What are mutagenic agents? What is a homologous pair of chromosomes? What is a Chromosome Mutation? ● Increase rate of mutation. ● Carry the same genes In animals, homologous pair of chromosome do not separate in meiosis, so either inherit one extra or one less chromosome called non-disjunction Why might not all mutations result in a change to the amino acid sequence of encoded polypeptide? ** ● What does Meiosis produce? ● ● 4 genetically different cells, h aploid (half the amount of chromosome/DNA) Haploid allows for chromosome number to constant at each generation For cell fusion/ joining of gametes be Benefits of Meiosis? ● Produces gametes which will be used in sexual reproduction in animals & plants (2 gametes fuse to form a zygote, zygote develops into organisms) Stages of Meiosis? Interphase/Meiosis I/Meiosis II/Cytokinesis What happens to the chromosomes in meiosis? ● ● Interphase? After crossing over they produce new combination of alleles Separation of chromosomes causes varying combination of chromosomes G1: protein synthesis S: DNA replication (doubles set of DNA) G2: organelle synthesis Meiosis I? Prophase I: DNA coils to form chromosomes, nucleus breaks down, spindle fibres form, c rossing over occurs Metaphase I: homologous pair of chromosomes line up in middle of cell and attach to spindle fibre via centromere Anaphase I: spindle fibres pull, homologous pair of chromosomes separate to opposite sides by independent Meiosis II? Prophase II: DNA coils to form chromosomes, nucleus breaks down, spindle fibres form Metaphase II: chromosomes line up in middle of cell and attach to spindle fibre via centromere Anaphase II: spindle fibres pull, centromere splits, sister chromatids move to opposite sides by independent assortment Telophase II: chromatids uncoil, nucleus reforms (left with 4 genetically different nuclei) Cytokinesis? separating cell into 4 (each receives a nucleus and organelles/cytoplasm) How does Meiosis produce Variation? ** What is an allele? ** ● Different version of a gene ● ● Occurs in Prophase I of Meiosis I Chromosome from a Homologous pair twist around each other. Causing section of chromatids to break and rejoin with chromatid from sister chromosome What is crossing over? ** ● What is independent assortment? What happens to DNA mass in meiosis? - in Anaphase I of Meiosis I – the homologous pairs of chromosomes separate - in Anaphase II of Meiosis II – the chromatids separate - independent assortment produces a mix of alleles from paternal and maternal chromosomes in gamete quarters What happens to Chromosome number Halves in meiosis? Module 4: How does courtship behaviour increase probability of successful mating? 1. Recognition of same species 2. Recognition of opposite genders ● ● ● Disruption / Isolation causing speciation? ● ● ● ● What is stabilising selection? ● ● Isolation of two populations variation already present due to mutations; different environmental conditions leading to different features and hence different alleles different frequency of alleles; separate gene pools / no interbreeding; No change in environmental conditions The population on the extreme die out as they are not well adapted The range of population decreases There is an increase in population which are very well adapted. Selection against one extreme ● Shifted towards a favoured extreme ● Favours one characteristic ● The extreme population of the characteristic die ● Directional selection? What is a species? Species richness? What is Hierarchical Classification? What is Binomial Naming System? A group of organisms that can produce fertile offspring No. of different species in a community - large groups divided into smaller groups with no overlap domain, kingdom, phylum, class, order, family, genus, species member of groups have similar common features using Genus name and Species name to name organism Genus name first in capital, Species name second in lower case e.g. tiger = Felix tigris What is Phylogenetic Classification? ● Based on evolutionary relationships – how closely related different species are and how more recent common ancestor they are ● Amino acid sequence can be used to see which organisms have similar sequences so put together OR similar DNA sequence OR mRNA sequence If large difference then they diverged many years ago / not related. ● What is Biodiversity? What is Species Diversity? ● ● - variety in an ecosystem variety of habitats and variety of species number of different species number of individuals for each species ● ● What is Genetic Diversity? ● ● Benefit of high species diversity? The larger number of individuals in a species, the larger the genetic diversity due to a greater gene pool Difference in gene pools / genes OR difference in DNA base sequence Crossing over increases genetic diversity since it causes sections to have different alleles. This leads to new combinations of alleles. -Stable ecosystem - each species is less likely to become extinct (due to high genetic diversity) - & if a species does become extinct it will not affect the food chain as there are other species available How to measure Species Diversity for an area? Species Diversity Index takes into account the number of different species and how many individuals there are for each species the larger the species diversity index, the larger the species diversity How does deforestation lower species diversity? - (deforestation is the removal of trees for wood & space) decreases plant species diversity less variety of habitats less variety of food sources decreases animal species diversity How does agriculture/farming lower species diversity? - deforestation to make space for farm only grow a few plants & keep a few animal species selectively breed plants & animals use pesticides to kill other species What is Classification? What is Variation? Types of Variation? Causes of Intraspecific Variation? placing organisms into groups difference in characteristics between organisms intraspecific = differences between organisms of the same species interspecific = differences between organisms of different species Genetic Factors = same genes but different alleles (allele are different type/forms of genes) Environmental Factors Causes of Interspecific Variation? Genetic Factors = different genes and different alleles Environmental Factors Types of Characteristics? Discontinuous and Continuous Properties of Discontinuous Characteristics? Characteristics fall into certain groups with no overlap (e.g. blood group) – determined by genetics only (a single gene) Properties of Continuous Characteristics? What is natural selection and adaptation? ** What are the 2 types of selection? What is stabilising selection? Characteristics show a range (e.g. height) – determined by genetics (a few genes, polygenes) and environment variation in population of species (genetic diversity/genetic variation/variety in gene pool) new alleles arise by random mutation environment applies a selection pressure on the population those with favourable characteristics/favourable alleles/selection advantage/better adapted survive, the others die [natural selection] the ones that survive will reproduce, passing on their favourable alleles if this happens for many generations, then that characteristic will become most common – the allele will become more frequent [adaptation] stabilising and directional when the environment favours those with the most common characteristic – those on the extreme dies out the common characteristic increases in proportion the range (standard deviation) will reduce
