BIOLOGY (Key points) Cell Structure functions of organelles difference b/w plant & animal cells difference b/w prokaryotes (bacteria) & eukaryotes light microscope: magnification - x1000 resolution - 200 nm electron microscope: magnification - x10,000,000 resolution - 0.2 nm epg = sm magnification = image / actual Biological Molecules Benedict's test: blue --> green --> yellow --> orange --> brick-red reducing sugar test - heat in a water bath + equal parts of reagent and food sample non-reducing sugar test - test for reducing sugar, if negative then add dilute hcl (to hydrolyze) and heat in a water bath + then add NaOH to neutralize and benedict' reagent Iodine test: brown --> blue-black starch test Emulsion test: lipids test add sample to ethanol and shake - pour into water --> if cloudy (white ppts) observed, lipids are present Biuret test: blue --> purple protein test NaOH and cuso4 (biuret reagent) were added to the food sample Carbohydrates: maltose --> a-glucose (C1 oh down) sucrose --> a-glucose + b-fructose lactose --> a-glucose + galactose amylose (starch) --> unbranched + 1,4 a-glycosidic bonds + compact amylopectin (starch) --> branched + 1,4 & 1,6 a-glycosidic bonds + side chains rapidly digested by enzymes quick energy release glycogen ( animals) --> more branched than amylopectin + 1,4 & 1,6 a-glycosidic bonds +large but compact cellulose --> unbranched + 1,4 b-glycosidic bonds + inverted bonds (180°) + microfibril threads joined by hydrogen bonds + structural support Lipids: saturated --> animal fats + no C=C unsaturated --> plant fats + C=C + melt at lower temperatures (more the unsaturated bonds, weaker the imfs, less the energy required to overcome them) triglycerides --> non-polar + glycerol & 3 fatty acids (3 ester bonds in condensation reactions) + used as energy reserves phospholipids --> one fatty acid replaced by phosphate head which is polar + hydrophobic tails face inward while hydrophilic heads face outward towards water + form partially permeable membrane Proteins: amino acids --> monomers + have amine group (nh2), Carboxylic acid group (cooh) & variable R group primary structure--> sequence & no. of amino acids secondary --> a-helix & b-pleated sheet + has hydrogen bonding (temp), ionic bonds (pH) & disulfide bridges (reducing agent) tertiary --> 3D shape + globular - soluble & metabolic role + fibrous - insoluble (usually) & structural role quaternary --> 2 or more polypeptides haemoglobin --> quaternary (2 a-globin chains & 2 b-globin chains) + Fe2+ haem group + at a time 8 oxygen atoms can be attached collagen --> quaternary (3 polypeptides) helical structure (triple helix) + every third is glycine (smaller) tighter coiling + molecules run parallel so covalent bonds form as cross-links + flexible + large tensile strength Water: polar + hydrogen bonding condensation + hydrolysis (metabolic reactions) high specific heat capacity --> minimised temperature fluctuations (buffer) + aquatic life high latent heat of vaporization --> evaporation leaves a cooling effect (homeostasis) cohesion & adhesion --> transport up xylem + capillary action + high surface tension (mosquitoes lay eggs) Enzymes globular proteins: increase the rate of reaction by lowering activation energy - provide an alternative pathway for the reaction can be reused lock & key theory --> active site and substrate have complimentary shapes & form enzyme-substrate complex induced fit theory --> active site of the enzymes molds around the substrate to become complementary Factors affecting: enzyme concentration --> rate increases as enzyme concentration increase more active sites to form complex till a certain point after which substrate concentration becomes limiting factor substrate concentration -->as conc increases, rate increases till enzyme concentration becomes the limiting factor temperature --> rate increases till the optimum temperature is reached when it is the highest and then starts to decrease as the enzyme denatures pH --> Enzymes denature if pH increases or decreases from optimum the concentration of competitive reversible inhibitors --> As it increases, the rate decreases as the active site becomes temporarily blocked non-competitive --> concentration increases, rate decreases as the shape of enzyme altered rate measured by calculating the increase in product or decrease in reactant per unit of time Inhibition: competitive --> inhibitor binds to the active site so substrate cannot bind to it + reversed by increasing substrate concentration non-competitive --> inhibitor does not bind to the active site but someplace else on the enzyme, changing its shape so that the active site changes feedback --> end-product binds to the enzyme stopping the pathway until the concentration of the product decreases reversible --> competitive/non-competitive Once removed, inhibition stops and the enzyme works again Michaelis-Menten Equation: Vo = V-max*(s) / Km+(s) V-max --> maximum rate of reaction V --> velocity of enzyme reaction S --> concentration of substrate Immobilization: difficult to separate the enzyme from the product solution immobilized by attaching to an insoluble and inert material enables to be reused + reaction to flow continuously + cheaper (may cost extra to immobilise) Cell Membrane & Transport all cells and some organelles are surrounded by a partially permeable membrane membrane composed of a sea of phospholipids with protein molecules controls movement of substances in & out of the cell/organelle + receptors for cell signaling the fluidity of the membrane and the arrangement of the proteins --> fluid mosaic model cholesterol --> stabilizes fluidity - high temperature, decreases fluidity + low temperature, increases fluidity channel protein (intrinsic) --> facilitated diffusion of polar molecules and ions carrier proteins (intrinsic) --> allow active & passive transport + change shape when molecule enters cell-signaling --> specific ligands are released that are transported to the targeted cell where they bind to the specific receptors on the cell surface membrane - a response is produced that causes further reactions permeability affected by heat (temp increases permeability increases) + pH (permeability decreases as pH rises or falls from 7) + ethanol (increases permeability) diffusion + facilitated diffusion + osmosis + active transport + cytosis solute potential --> negative - as concentration increases water potential becomes more negative as the surface area to volume ratio increases, the rate of diffusion/osmosis increases Mitosis produces genetically identical daughter cells --> no genetic variation for growth + replacing dead cells + repairing + asexual reproduction telomeres prevent the loss of genes during DNA replication Cell Cycle: interphase --> makes RNA, enzymes, and other proteins needed for growth G1 - grows + prepares for DNA replication S - DNA replication G2 - growth continues + new DNA checked + prepares for mitosis mitosis -->forms two identical cells prophase - centrosomes (not in plants) to opposite poles + chromatin condenses + nucleolus disappears + asters & spindle fibres form metaphase - spindle microtubules arrange chromosomes at the equator + each chromosome splits at the centromere anaphase - chromosomes pulled to the opposite poles by microtubules spindle fibers contract telophase - nuclear envelope reforms + nucleus divides + chromosomes at poles cytokinesis --> division of cytoplasm plants - cell plate of cell wall forms across the equator animals - contractile ring forms that push the cell membrane inwards till it closes Stem Cells: undifferentiated cells - can be specialized stem cells undergo cell division & are used for cell replacement & tissue repair - once specialized, they stop dividing pluripotent --> embryonic multipotent --> bone marrow totipotent --> zygote & spores uncontrolled division - formation of tumor --> causes cancer (as a result of carcinogens/mutagens) malignant tumour --> can spread + benign --> do not spread Nucleic Acids & Protein Synthesis Nucleic Acids: contain genetic information + polymers of nucleotides + organic base, pentose sugar & phosphate group A & G - purine T, U & C - pyrimidine A=T/U G≡C difference between RNA & DNA 1. uracil & thymine 2. ribose & deoxyribose 3. single strand (short) & double helix 4. translation & transcription DNA structure --> double helix + *polynucleotides joined by hydrogen bonds between complementary bases + 2 strands lie antiparallel + *purine bonds with pyrimidine + *nucleotides joined by phosphodiester bonds *(common for DNA & RNA) semi-conservative replication - double helix unwinds --> hydrogen bonds break using DNA helicase --> the strands are used as templates and complementary base pairing occurs with free nucleotides --> adjacents nucleotides joined by phosphodiester bonds via DNA polymerase DNA polymerase --> works only in 3' to 5' direction - leading strand + lagging strand - 5' to 3' direction forms Okazaki fragments (joined by DNA ligase) Protein Synthesis: proteins are polypeptide chains + coded for by a gene (part of DNA) genetic code is universal + triplet code (3nucleotides) codes for an amino acid or a start/stop codon transcription: DNA uncoils (hydrogen bonds broken by DNA helicase) --> free nucleotides bind to the template strand via base pairing --> adjacent nucleotides joined by RNA polymerase --> mRNA detaches and moves out through the pores translation: mRNA attaches to a subunit of ribosome --> tRNA (has an attached amino acid with it) attaches to the mRNA due to complementary anticodon --> another tRNA molecule binds to the second codon amino acids joined by peptide bonds --> tRNA detaches from the amino acid leaving a polypeptide chain Gene mutations: occur as a result of a change in the base sequence of DNA - altered mRNA, tRNA & polypeptide caused by mutagenic agents - chemicals and ionizing radiation substitution - a nucleotide substituted by another insertion - nucleotide added to the DNA strand deletion - removal of a nucleotide from the strand effects: 1. nonsense - mutation making a stop codon so polypeptide won't be formed 2. missense - different amino acid coded for, polypeptide chain changed 3. silent - different codon but codes for the same amino acid so no effect on the chain Transport in Plants to ensure all cells receive sufficient nutrients -diffusion not possible due to small surface area to volume ratio + multicellular --> aid growth & development Xylem: located towards the inside transport water & minerals and provide structural support (lined with lignin) made up of dead tissues with open ends (continuous column) contain pits - sideways branching to transport to smaller stems Phloem: located towards the outside translocate nutrients made up of living cells + sieve tube elements & companion cells (ATP production for active sucrose loading) + companion and sieve tube linked via plasmodesmata Transpiration: plants absorb water through the roots which move up through the plant and are released into the atmosphere as vapors through leaf stomata and diffuse into the air transpiration stream is the movement of water so that photosynthesis is enabled + supplies with minerals + controls temperature rate measured by photometer - water lost replaced by water from the capillary tube factors that affect rate: number of leaves + number/size/position of stomata + waxy cuticle + amount of light + temperature + air movement + water availability + humidity Xerophytes --> plants adapted to live in dry conditions - small leaves + densely packed spongy mesophyll + thick cuticle + closed stomata + hairs & pits + curled leaves + water storage in parenchyma tissue + large extensive roots Movement of Water: root hair cells to xylem tissue - water potential gradient + root hairs increase s.a + minerals by active transport across cortex 1. symplast pathway - water enters cytoplasm through plasmodesmata from the cytoplasm of one cell to the other 2. apoplast pathway - water moves through the water-filled spaces between cellulose molecules in the cell wall 3. Casparian strip - a part of root endodermis that cannot be penetrated by water + water movement continues by symplast pathway only from this point onwards xylem vessel to mesophyll cells - down w.p gradient --> aided by root pressure (movement of ions into xylem via active transport so w.p decreases so osmosis into the vessel, thus pushing it upwards) + surface tension & cohesion (attraction b/w water molecules as a result of hydrogen bonding) + capillary action (adhesion) Translocation: transport of assimilates dissolved in water from the source to sink sucrose enters phloem by active loading - proton pumps of companion cells use ATP to transport hydrogen ions creating a diffusion gradient facilitated diffusion of sucrose molecules into the sieve element decreasing the water potential as concentration increases movement of water into the element via osmosis increasing the hydrostatic pressure so water (and dissolved sucrose) moves to an area of low hydrostatic pressure aka the sink mass flow of water from the source to sink *difference between xylem and phloem *difference between plant and animal transport *difference between artery, vein, and capillary Transport in Animals mammals have a closed double circulatory system (passes through the heart twice) + consists of the heart, blood vessels & blood Blood Vessels: tunica interna - a very smooth single layer of flat cells (smooth endothelium - reduce friction) tunica media - consists of smooth muscles (contract & relax to regulate flow), collagen fibers (stretch to prevent rupture) & elastic fibers tunica externa - collagen & elastic fibers arteries - narrow lumen + thickest media & external + generally thicker (high pressure blood) + contract and relax to alter blood pressure arterioles - branched out arteries + thinner + less muscular capillaries - smallest blood vessels + site of metabolic exchange + one cell thick (fast exchange) + enable efficient diffusion ( narrow lumen, large s.a & slow blood flow) venules - larger than capillaries but smaller than veins veins - wide lumen + thin-walled (low pressure blood) + valves to prevent backflow + no pulse (less smooth muscle & elastic tissue) Tissue Fluid: contains dissolved oxygen & nutrients + waste products - enables the exchange of substances hydrostatic pressure forces blood fluid out of capillaries - tissue fluid does not contain large proteins & red blood cells pushed back into the capillaries on the venular end due to osmosis left behind fluid carried to the lymphatic system - less oxygen & nutrients + lymph nodes (filter out bacteria & foreign materials) brings waste products + part of the immune defense system water is the main component *difference between blood, tissue fluid, and lymph fluid Cardiac cycle: the ventricles pump blood at a higher pressure they o have thicker walls - the left ventricle is even thicker as it pumps blood to the whole body myogenic muscle - able to contract on its own SAN (pacemaker) initiates a wave of electrical impulse that causes the atria to contract (atrial systole - av valves open) --> ventricle contraction delayed by the presence of tissue that is unable to conduct the wave --> wave reaches AVN located between the two atria which send the wave to the ventricles --> puree tissue at the base of ventricles that carry the wave upwards causing the ventricles to contract (ventricle systole av closes + semilunar opens) atrial systole --> ventricle systole --> ventricle diastole - both atria & ventricle relax + semilunar close Haemoglobin: 2 b-globin + 2 a-globin + haem group --> each can carry 8 oxygen atoms affinity depends on oxygen concentration + partial pressure + saturation dissociation curve illustrates the change in hemoglobin saturation as partial pressure changes + Bohr effect - increase in co2 concentration shifts the curve towards the right carbonic anhydrase (enzyme in the blood) - helps oxygen to dissociate from oxygen and bind to co2to carbaminohaemoglobin + catalyzes the reaction between co2 and water to form carbonic acid --> hydrogen ions released + combine with hemoglobin to form hemoglobin acid (dissociation encouraged) saturation - after binding to the first oxygen molecule, an affinity for binding with the following increases due to a change in shape at high altitudes, RBC count increases - fewer oxygen saturation due to lower partial pressure --> more hemoglobin for oxygen to bind to chloride shift - maintain cell's electrical balance + low co2 concentration --> carbonic anhydrase catalyzes the breakdown of carbonic acid to water and co2 --> bicarbonate diffuses into the RBCs and reacts with hydrogen ions so carbonic acid forms --> co2 diffuses from the blood into the lungs --> chloride ions from rbcs into the plasma down the electrochemical gradient Gas Exchange: single-celled organism --high diffusion + s.a to volume ratio multicellular organisms --> specialised exchange surfaces + of co2 and o2 + small s.a to volume ratio efficient exchange - large surface area = thin +good supply/ventilation Mammalian exchange system: lungs - located in chest cavity + can inflate + large s.a + surrounded by ribcage external & internal intercostal muscle work antagonistically the diaphragm separates the chest from the abdomen air enters through nose --> trachea --> bronchi --> bronchioles --> alveoli --> capillaries -> rbcs --> body cells trachea - C shaped cartilage + goblet cells + smooth muscle + cilia bronchus - irregular blocks of cartilage + goblet cells + smooth muscle + cilia terminal bronchiole - smooth muscle + cilia respiratory bronchiole - only a few cilia alveoli - large s.a + one cell thick walls + elastic fibres + squamous epithelial cell lining + movement of blood creates a steep concentration gradient - cartilage --> support + prevents collapse if pressure drops - ciliated epithelium --> move mucus along to prevent infection - squamous epithelium - allow gas exchange + thin + large s.a - goblet cells -->mucus secretion to trap bacteria + swept away by cilia - smooth muscle --> contract to contract airway controlling the air to & from alveoli - elastic fibres --> stretch during exhalation + recoil during inhalation to control airflow inhalation - diaphragm contracts and moves downwards + ribcage upwards & outwards + internal intercostal muscles contract & external relax + lungs expand Infectious Diseases Cholera --> Bacteria + Vibrio cholera + water & food + severe diarrhoea, loss of water & salts, dehydration and weakness + microscopic analysis of faeces + oral rehydration therapy + improve sanitation & hygiene Malaria --> Protoctist (eukaryote) + Plasmodium falciparum, P.vivax, P.ovale & P.malariae + infected female mosquitoes (Anopheles) + fever, anemia, nausea, headaches, shivering and sweating + microscopic analysis of blood + preventative drugs + reduce the number of mosquitoes (by destroying habitat) and prevent biting (use of nets and repellent Tuberculosis --> Bacteria + Mycobacterium tuberculosis + airborne water droplets from coughing/sneezing + racking cough, coughing blood, chest pain, shortness of breath, fever, sweating and weight loss + microscopic analysis of sputum+ combination of drugs + use of the vaccine, cover mouth & nice when near infected and infected to quarantine HIV/AIDS - Virus + Human immunodeficiency virus + sexually transmitted, via body fluids and needle sharing + testing blood/saliva/urine for antibodies + no cure or vaccine + take medication, use condoms (protected intercourse), use a clean needle and screening blood donations Antibiotics: Bactericidal antibiotics - kill bacteria by destroying cell walls causing them to burst Bacteriostatic antibiotics - inhibit growth by stopping protein synthesis and the production of nucleic acids some bacteria become resistant as a result of natural selection + pathogens evolve adaptations + incomplete course so some survive - form resistive strain --> different antibiotic used to kill them do not work on viruses - different structure (no cell wall or protein synthesis) Immunity Immune Response: physical barriers - skin + stomach acid + gut & skin flora nonspecific response - inflammation + lysozyme (in tears & mucus) + interferon + phagocytosis Phagocytosis - specialized wbc engulf pathogens + lysosomes in phagocytes hydrolyze the pathogen --> antigens presented on the surface of phagocyte + other immune system activated specific response - B cells + T cells B cells - mature in bone marrow + humoral response --> triggered when encounters matching antigen --> engulfs the pathogen and displays antigen --> stimulated so B cell with particular antigen will divide so some form memory cells while others form plasma cells --> plasma cells secrete antibodies that target the antigen T cells - mature in thymus gland + cell-mediated response --> specific cell receptors have a similar structure to antibodies - T helper --> divides so some form memory + some secret cytokines that stimulate T killer and B cells to divide and form plasma cells to make more antibodies - T killer --> divides so some form memory + some punch holes in membranes of infected body cells --> vacuoles in killer contain toxins Antibodies - Y-shaped glycoproteins that bind to antigens to trigger an immune response Monoclonal antibody production - inject a mouse with antigen --> mouse produces antibodies --> spleen cells removed --> spleen cells bind with myeloma cells to produce hybridoma cells --> hybridoma divide to produce antibodies that are all specific to original antigen - used in the treatment of cancer immunity - natural active --> being exposed to antigen and producing own antibodies - natural passive --> crossing of mother's antibodies through placenta/breast milk - artificial active --> acquired through vaccination that stimulates immune response --> help provide long-term immunity & prevent epidemics - artificial passive --> antibodies injected into the body (tetanus)
