B4 and B5 model answers

7/30/2019 B4 and B5 model answers

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B4 Model Answers

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PopulationAll organisms of one species in a habitat/area/place/at one time;

CommunityA collection of different populations of species living in the same ecosystem

EcosystemThe community and the abiotic/physical environment;

Ecological NicheThe niche of an organism refers to its

biotic role (what it feeds on and whatmay feed on it) and its abiotic role(where it lives in the habitat in terms ofthe abiotic conditions it requires).

Adaptions to its nicheThe organism has an adaption that others dont, occupying a different nicheReducing competition

TransectLine (through habitat) along which organisms are sampled/measurements are taken;

Should be used when there is a change in the habitat/environment;

How to place quadratsMethod of positioning quadrats,E.g. Find direction and distance from specified point/find coordinates on a grid / split area into squares;Method of generating random numbers;E.g. From calculator/telephone directory/numbers drawn from ahat;

How to use point quadrats to find the distribution of organisms

Transect placed downPoint quadrat frame placed at regular intervalsRecord species touching pointsCalculate percentage coverUse statistical test to show significance

How to decide how many quadrats to useCalculate running mean/description of running mean;When enough quadrats, this shows little change/levels out (ifplotted as a graph);Enough to carry out a statistical test;A large number to make sure results are reliable;

Need to make sure work can be carried out in the time available;


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Mark release recapture1 Sample of ground beetles captured and counted (a);2 Released and second sample captured;3 Count total number of beetles (B) and number marked (b);4 Total population (A) estimated from the relationship a /A =b/B

5 Detail of method e.g. pitfall trap/marking with tippex;6 Refinement to ensure greater accuracy e.g. large number/markingin position such that does not affect survival;

Assumptions when using mark, release, recapturemixes randomly / completely inpopulation;marking is not toxic / does not wear off;no migration / emigration / immigration;no change in population size betweensamples / life span longer than timebetween release and recapture;

no births or deaths;not trap-happy / trap shy

Why using traps to capture organisms improves reliability of dataRules out differences in changes in the population due to births, deaths or migration

Explain why a survival curve looks like it does (use data)Developed countries:

Better medical healthcareLess diseaseLow death rate among the young

Less developed countries:More diseasePoor sanitationPoor medical healthcareHigh death rate among the young

Uses of statistical testsDetermines the probability of the results being due to chanceEnables null hypothesis to be accepted or rejectedDetermines whether correlation is biologically significant

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How ATP is produced using light in LDP1 Light (energy) excites/raises energy level of electrons inchlorophyll;2 Electrons pass down electron transfer chain;3 (Electrons) reduce carriers/passage involves redoxreactions;4 Electron transfer chain / role of chain associated withchloroplast membranes / in thylakoids / grana;5 Energy released / carriers at decreasing energy levels;6 ATP generated from ADP and phosphate/Pi /

phosphorylation of ATP;


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Why does the inhibition of electron transfer decrease the uptake of carbondioxide?No ATP produced during electron transfer chainNo reduced NADP produced

How carbon dioxide is converted to TP in the LIPCarbon dioxide combines with RuBPTo produce two GPReduced to TPRequires ATPAnd requires reduced NADP

How chloroplast is adaptedContains chlorophyll / pigments for light absorption;Different pigments to absorb different wavelengths;Stacking / arrangement of grana/thylakoids maximises light catchment;Stroma contains enzymes for photosynthesis;

Outer membrane keeps enzymes in chloroplast;Starch grains / lipid droplets store products of photosynthesis;Ribosomes / DNA for enzyme/protein synthesis;Shape of chloroplast gives large surface area for CO2, absorption.

How Leaves adapted to photosynthesiseLarge surface area to collect solar energy;transparent nature of cuticle to allow light penetration;position of chlorophyll to trap light;stomata to allow exchange of gases;thin / max. surface area to volume ratio for diffusion of gases;

spongy mesophyll / air spaces for carbon dioxide store;xylem for input of water;phloem for removal of end products;

Describe how microorganisms make carbon available to plantsExtracellular digestionStarch to monosaccharides/glucoseRespire the product of digestion (glucose)Produce carbon dioxide from respiration

Lower carbon:nitrogen ratioMore protein is being formed

As nitrogen is used to make amino acids

Why increase in temperature causes increase in rate of photosynthesisEnzymes are involved;extra kinetic energy / molecules move faster;molecules collide more often / more enzyme - substrate complexes formed;

Describe the role of the electron transport chain1 electron transport chain accepts excited electrons;2 from chlorophyll / photosystem;3 electrons lose energy along chain;

4 ATP produced;5 from ADP and Pi;6 reduced NADP formed;


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7 when electrons (from transport chain) and H+ combine with NADP;8 H+ from photolysis

Explain why the increase in dry mass is less than the amount of 6 Carbonsugars

1 some hexose/biomass/eq. used in respiration;2 CO2 produced (is lost to air);3 some parts of the plant are eaten;4 some parts lost to decomposers / in leaf fall;

Suggest why the deep ocean has a lower productivity than the shallowsea.Fewer nutrients available;Limited light penetration;No organic matter from terrestrial sources;Other limiting factor explained

Reasons for the difference in the amount of light energy reaching the plants,and the energy in biomass of these plantslight reflected;

light misses chlorophyll/chloroplast/transmission through leaf;wrong wavelength;respiration (by primary producer);

inefficiency of photosynthesis;

Why is the concentration of carbon dioxide different at different heights aboveground in a forest?

High concentration of carbon dioxide linked darknessNo photosynthesis in the darkPlants still respire in the darkIn light, the rate of photosynthesis is greater than that of respirationDecrease in carbon dioxide concentration with lightAt ground level, fewer leaves/ less photosynthesising tissue/ less light

Why do plants have to produce ATP in respiration as well as photosynthesis?In the dark, there is ATP production by photosynthesisSome tissues unable to photosynthesiseATP cannot be moved from cell to cellPlant uses more ATP than produced by photosynthesis

ATP for active transportATP for synthesis

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Why is ATP useful in many biological processes??Releases energy in small manageable amountsBroken down in one stepMakes energy available rapidlyAdds phosphateMakes phosphorylated substances more reactiveCan be reformed


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How is ATP adapted to make it a suitable source of energy in biologicalprocesses?Energy released in smallSolubleInvolves a single reaction

Why do humans produce so much ATP every day?ATP is unstableATP cannot be storedATP is used for muscle contraction/active transport etcATP only releases a small amount of energy at a time

Human Anaerobic RespirationPyruvate forms lactate;use of reduced NAD / NADH;regenerates NAD;NAD can be re-used to oxidise more

respiratory substrate / correct e.g. / allowsglycolysis to continue;can still release energy / form ATP whenoxygen in short supply / when no oxygen

Link ReactionPyruvate reacts with coenzyme A;To produce acetyl coenzyme A / acetyl coA;And carbon dioxide produced;NAD is reduced / reduced NAD is formed;Acetylcoenzyme A combines with a 4C molecule (in the Krebs cycle);

Why CO2 production greater in anaerobic conditions(Anaerobic respiration/respiration with nitrogen) lessefficient/produces less ATP;More anaerobic respiration/ more glucose/substrate must berespired to produce same amount of ATP (so more carbon dioxideproduced);

How ATP produced in MITOCHONDRIAoxidation of / removal of electrons/removal of hydrogen from pyruvate / 6or 5 carbon compound;

production of reduced NAD / FAD;in matrix of mitochondria;electrons passed to electron transportchain / used in oxidative phosphorylation/ description of electron transfer;on cristae / inner membrane;linked to ATP production;ATPase / stalked particles involved;electrons lose energy as passed alongchain / electron carriers arranged in orderof decreasing energy levels;substrate level production of ATP

Role of inner membrane of mitochondria for producing ATP


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Electrons transferred down the electron transport chainProvides energy to take protons into space between membranesProtons pass back through membrane into the matrixEnergy used to combine ADP with phosphate to form ATP

How increasing temperature affects rate of respirationRespiration controlled by enzymesRate increases with temperatureMore kinetic energyFewer collisions between the substrate and the active siteFewer E-S complex formed

Measuring rate of respiration using a respirometer, why does the colouredliquid move?Oxygen taken up by organismCarbon dioxide absorbed by substance (named)Decrease in pressure

What measurements should be taken to calculate the rate of respirationDistance the coloured liquid movesTime takenMass of woodlouseDiameter of the capillary tube

Gross productivity = Net productivity + Respiration

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Why efficiency of energy transfer changes between trophic levels1 Some light energy fails to strike/is reflected/not ofappropriate wavelength;2 Efficiency of photosynthesis in plants is low/approximately2% efficient;3 Respiratory loss / excretion / faeces / not eaten;4 Loss as heat;5 Efficiency of transfer to consumers greater than transfer toproducers/approximately 10%;6 Efficiency lower in older animals/herbivores/ primary

consumers/warm blooded animals/homoiotherms;7 Carnivores use more of their food than herbivores;

Why is the energy efficiency of single celled producers to primary consumerssometimes higher than usual?Single celled organisms are more digestible as they contain less celluloseAll of producer eater/ parts of a plant are not eatenLess energy is lost from the producer by heat or respiration compared to a plant

Why not all light isnt used for photosynthesisDoesnt hit leaveslight is wrong colour / frequency /

wavelength / does not strike chlorophyllmolecule / chloroplasts / there is another


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limiting factor

How energy is lost between consumersHeat / respiration:muscle contraction;

faeces / indigestible material / foodnot eaten;excretion

Why food chains rarely exceed levelssome energy lost at each stage in the foodchain / transfer of energy not 100%efficient / lost in respiration;only a limited amount of energy isavailable / at each stage less is available fornext stage / little energy left at top offood chain

How intensive rearing of livestock increases net productivity1 Slaughtered when still growing/before maturity/while youngso more energy transferred to biomass/tissue/production;2 Fed on concentrate /controlled diet /controlledconditions/so higher proportion of (digested) foodabsorbed/lower proportion lost in faeces / valid reason foraddition;3 Movement restricted so less respiratory loss / less energyused;4 Kept inside/heating/shelter / confined so less heat loss / nopredators;

5 Genetically selected for high productivity;

Advantages/disadvantages of biological controlAdvantages

1. specific (to one pest);2. only needs one application / reproduces;3. keeps population low;4. the pests do not develop resistance;5. does not leave chemical residues in environment;6. can be used in organic farming;

Disadvantages

7. does not get rid of pest completely;8. may become a pest itself;9. slow acting / takes time to reduce pest population

Bioaccumulationpest take in pesticide;predators eat large numbers of pests;bioaccumulation idea / pesticide cannotbe excreted / remains in the body / storedin fat / not broken down

Benefits of leguminous plants on productivity


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Nitrogen fixing bacteria / named e.g.;in root nodules (of legumes);convert nitrogen to ammonium / organic compounds (in legume);released on decomposition;and converted to nitrates; less need for fertiliser;

Why would there be a higher total yield if you grow many different species,rather than one species??Different species have different root lengths;Mineral ions/water can be obtained from different depths;Shade plants grow as well as those needing full sunlight;Pests tend to be specific;Pests will not destroy total crop in mixed system;Less fallow time;

Describe and explain the effect of adding fertiliser on the biomass of the

plants.increase growth of both weeds and cereal crop;inorganic nutrients/minerals not a limiting factor /more inorganic nutrients available

Explain why the application of herbicide increases the final yield of the crop.removal of competition by weeds

What factors do you need to consider when doing an experiment about cropsYieldAnimalsCost of fertiliser

Method/frequency of application

Why is more energy used when its colder??More heat energy lostEnergy required maintaining their body temperatureBy respiration

Give one advantage of using natural fertiliser rather than artificial fertiliserContains a wider range of elementsProduction of artificial fertiliser energy-consumingLess leaching/slow release of nutrients

How do farming practises increase the productivity of agricultural cropsFertilisers are added to the soilNitrates/ nitrogen is required for proteinsPhosphorus is required for ATP and DNAPesticides prevent consumption of the cropsSelective breeding increases productivityGreenhouses enhance temperature/light/Carbon dioxide levelsPloughing aerates the soilAeration decreases denitrification and increases nitrificationCrop rotation keeps the soil fertileIrrigation removes water as a limiting factor

Protection of crops from birds/pests by cover/netting


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How does deforestation and burning vegetation affect carbon dioxideconcentrationCarbon dioxide concentration increasesLess vegetation so less photosynthesisLess carbon dioxide removedCombustion releases carbon dioxide

How microorganisms and detritivores make carbon available to plants1. Microorganisms are saprobionts/saprophytes;2. Detritivores increase surface area by ingesting the organic matter3. Microbial decomposers break down the organic matter4. Secrete enzymes (onto dead tissue) / extracellular digestion;5. Absorb products of digestion/smaller molecules/named relevant substance;6. Respiration (by microorganisms) produces carbon dioxide;

7. Carbon dioxide taken into leaves;8. Through stomata;9. Used for photosynthesis

Difference between the way detritivores and decomposers obtain theirnutrientsDecomposers secrete enzymes / onto organic matter/ food/extracellular breakdown;Detritivores ingest / eat/ take in organic matter/food first;

Why do detritivores increase the activity of decomposers1. Break down large pieces of organic matter, providing a greater surface area formicrobial activity2. Add products of excretion/more nutrients/nitrogen / higher nitrogen carbon ratio;aeration by e.g. tunnelling;3. increases oxygen content for respiration of microorganisms;

Eutrophicationgrowth of algae / plants increased;death of submerged algae / plants;more bacteria / decomposers /decomposition;respiration uses oxygen;

aerobic animals die

What is meant by the law of diminishing returns??increased application of fertiliser does not increase yields;therefore uneconomic

Increase in nitrate concentrations in rivers1. Fertiliser run-off2. Nitrification3. Sewage effluent4. Nitrogen fixation

How can algal growth decrease nitrate concentrationAbsorption of nitrates by algae


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Used to synthesise amino acids

Advantanges of Inorganic Fertiliserseasy to handle / apply / transport / store;known chemical content / can supplyspecific needs;easy to control mass that is added / lessmass needed;releases ions / nutrients quickly / soluble

Disadvantages of Inorganic fertilisersexpensive / more readily leads toeutrophication /environmentally damaging / usesresources to make it / does not add to soilstructure / lacks some nutrients

Explain how deforestation could lead to a decrease in biodeveristyLoss of habitat / nest sites / shelter / niche; ignore homesLoss of food;Exposure of soil leads to erosion / leaching of ions;Change in (micro)climate / levels of light / temperature / humidity;Animals move away / higher death rate / extinction;

Describe the role of bacteria in making nitrogen available to plantsSaprophytesBreak down proteins/DNABy extracellular digestion/ releasing enzymesInto ammonia

Ammonia converted to nitriteNitrite is converted to nitrateBy nitrificationOxidation

How does less ploughing mean more carbon is stored in the soilLess oxygen can enter the soil (from the air);For saprophytes / soil microorganisms / bacteria / fungi / decomposers / correctlynamed soil organisms;For use in aerobic respiration;Less breakdown of organic matter / humus / dead plants / dead animals / other e.g.;Less carbon dioxide released / formed;

Ploughing increases the activity of nitrifying bacteria in the soil. Why? Andhow does this benefit plants?

Oxygen enters the soil / use of oxygen;Nitrifying bacteria are aerobic;Ammonia / ammonium ions to nitrite;Nitrite to nitrate;Nitrate is absorbed / used by plants;To make named organic-N e.g. protein / amino acids / DNA /ATP / NAD(P) / chlorophyll;

Increased yield / growth;


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Why do nitrogen fixing bacteria need a high rate of respiration??Provides ATP for the nitrogen fixationMore enzyme producedWhich removes the oxygen

Why do plants grow more slowly, getting nitrogen from nitrogen-fixingenzymes, rather than from fertiliser??ATP is required for nitrogen fixing/ reducing nitrogenLess ATP is available for growth/protein synthesisSo greater rate of respiration required to make up for this

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Succession

change in community over time;eitherdue to environmental / abioticfactors / named abiotic factor;orconditions change due to speciespresent

How do the species that are present change during succession??Species change the environmentLess hostileSpecies are better competitors

Climax Communitystable community / no furthersuccession / final community

Limits of the size of a population of a climax community1. named nutrient availability;2. numbers of producers providing energy (for a food chain);3. light intensity affecting the rate of photosynthesis;4. disease killing (weaker) members of species;5. space for nest building / niches;

6. reproductive rate balancing death rate;7. competition for a named limited resource;8. (intra and interspecific) competition explained;9. predation described;

Description of Succession1. Colonisation/pioneering2. Microscopic plants at start3. Death/decomposition4. Named change in environment e.g. increase in organic matter/stabilisation5. New species colonise once there is a change6. Increase in biodiversity

7. Increase in total biomass/more niches8. Increase in nutrient availability


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9. Change from more extreme conditions/ more stability10. Climax community

How does farming prevent successionMaximum of 4 marks, two for named practices and two forexplanations of effects:

1. e.g. crops are planted (not native plants);these compete with native plants;2. ploughing returns to bare soil;destroys herbaceous plants/tree/shrub seedlings;3. grazing by farm animals;

destroys herbaceous/shrub seedlings/communities.

Why is it an advantage to have seeds that germinate better when temperaturefluctuates?Bare soil temperature fluctuatesSo theres more bare soil at the start of succession when there is few plants

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How do you know if 2 alleles are from the same gene??The frequencies add up to 1

Recessive AlleleOnly expressed in phenotype if homozygous

Co-Dominant AlleleBoth expressed in phenotype if both are present

Why observed phenotype ratios are not always same as theoretical ratioschance related to mating;random fusion of gametes;small sample size;differential mortality

Using a diagram to show a particular allele is recessiveParent (name or number) show the dominant but offspring show recessiveSo parents must be heterozygous

How two isolated populations of a species may become different speciesgeographical isolation of two populations;no interbreeding / gene flow;range of habitats / environmental conditions;different selection pressures in separate populations;variation among species caused by mutation;some more suited to environment than others / differential survival;Those with advantageous alleles survive and breed;beneficial allele passed on so frequency of advantageous alleles increases in the gene pool;populations become genetically different

populations unable to produce fertileoffspring / reproductively isolated


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What does Hardy Weinberg predictThe frequency/proportion of alleles (of a particular gene);Will stay constant from one generation to the next/over generations / no genetic change over

time;Providing no mutation/no selection/population large/population genetically isolated/mating atrandom/no migration;

Hardy Weinberg AssumptionsNo selective advantage / All genotypes equally fertile;Large population;Random mating; (IGNORE random fertilisation)No mutation;No emigration/immigration;

Natural Selection

variation between members of population/species;predation/disease/competition results in differential survival;some have adaptations that favour survival;survive to reproduce/have more offspring/ pass ontheir alleles/genes;produces changes in frequency of allele /gene pool/genotypes/phenotypes;

Evidence for stabilising selectionFew organisms survive at the extremes/most survive from the middleof the range;

How Science Works

Why important to check repeatability of resultIncreases the reliability of the measurements;If measurements are repeatable, differences less likely to be dueto measurement/personal error/ anomalies unlikely;

Why use a statistical test(A statistical test) determines the probability of results being due to

chance;Enables null hypothesis/description of null hypothesis to beaccepted/rejected;Determines whether correlation/result is significant;

Accuracy and ReliabilityAccurate means without error/free from mistakes when callipers used;Reliable means that figure can be reproduced when measurementRepeated/show little variation about true value;

Why good to have large sample sizeallows anomalies to be identified /

increases reliability (of means /averages / results);


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allows use of statistical test

Why quadrats should be placed at randomTo avoid bias/obtain representative results so statistical tests can be applied

Why Standard Deviation better than Rangerange just shows highest and lowest /SD shows spread of majority;extreme values give false impressionof variation / SD less affected byextreme values;

B5 Model Answers

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Kinesisrandom movements = 1 mark, e.g. degreeof turning / number of turns depends onstrength of stimulus / on temperature /allow specific reference to more turning at35 than at 30 / non-directional stimulus/ response

Reflexrapid response to stimulus;which is automatic / involuntary / not

under conscious control;

Importance of reflexesavoids damage to tissues;role in learning / homeostasis;posture / balance;escape from predators;finding food / mate;

How Exercise increase heart rateincrease in carbon dioxide fromrespiration;

decrease in blood pH / increase inhydrogen ions detected by chemoreceptors;


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in carotid / aortic bodies / medulla;(more) impulses to cardiac centre /medulla;(more) impulses (from medulla) alongsympathetic nerve;to SAN increasing heart rate.

How generator potential created in Pacinian Corpusclepressure deforms / stretches membranesodium channels;sodium ion channels / gates open;sodium ions enter causing depolarisation /generator potential created.

How rod cells allow us to see in darkseveral rods have connections with oneneurone / bipolar cell;

idea of summation (of generatorpotentials);exceed threshold;individual (generator potentials) do notexceed threshold;low intensity light breaks down rhodopsin

Why cone cells give greater visual acuityEach cone is connected to a specific neurone;light striking cone cells generating separate action potentials;

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Why Myelinated faster than non-myelinatednon-myelinated depolarisation occursalong whole length of whole membrane;myelinated depolarisation only occurs atnodes (of ranvier);impulse jumps from node to node /salutatory conduction;

Nervous vs Hormonalnervous system electrical impulses,

hormonal only chemicals;use neurones, use of blood;localised, widespread response;short-lived, long-lasting;rapid, slow response;

How resting potential maintainedmembrane more permeable to loss of potassium ions;limits entry of sodium ions;negatively charged proteins inside;sodium pump;

How action potential moves along neurone


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Depolarisation /reduced P.D. /70 to40 mV;to threshold;by local currents;increased permeability of membrane to sodium ions / sodium gates open;sodium ions enter;by diffusion;positive pd inside / eq via figures;then potassium gates open / permeability to potassium ions increases;potassium ions leave;by diffusion (ONCE only);resting potential re-established;

Transmission across synapseIncreased permeability of (presynaptic) membrane to calcium ions;

Ca 2+enter;vesicles fuse with membrane;exocytosis of / release of acetylcholine / neurotransmitter /

other named e.g.;diffuses across synaptic cleft;binds to receptors on postsynaptic membrane / side;increased Na + permeability / opens sodium channels / depolarisesmembrane / reference e.p.s.p.;acetylcholine broken down by acetylcholinesterase;

How Reflexes are rapid and autonomic

Rapid:

Only involves three neurones /receptor, relay and effector neurone;myelination / saltatory conduction;and two / a few synapses;chemical / synaptic transmission is slow OR electrical /nervous transmission is fast;

Automatic;does not necessarily involve passage to brain / only spinal cord;same pathway used each time;higher brain centres not involved / no thinking;

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Role of Ca2+ in contraction of myofibrilcalcium ions bind to / move tropomyosin;to reveal binding sites on actin;allowing myosin (heads) to bind to actin /actinmyosin cross bridge formed;activates ATPase / energy released fromATP;

Role of Phosphocreatinephosphocreatine allows regeneration ofATPunder anaerobic conditions;


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phosphocreatine releases Pi to join ADP;

How impulse arriving at neuromuscular junction causes sarcomere to contractentry of calcium ions (presynapticmembrane);

vesicles fuse with membrane / exocytosis /release TS;neurotransmitter diffuses;binds to receptors, postsynaptic /membrane / muscle membrane;depolarisation / sodium ions enter;release of calcium ions (from within themuscle);removes tropomyosin / bind to troponin;exposing binding sites on the actin;cross bridge formation / myosin binds;myosin head moves / pull the actin along;

rachet mechanism / description / detachand reattach;ATPase activated;

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Homeostasismaintaining a constant internal environment

Why Body Temperature must be maintained1. Body temp./37C is optimum temp for enzymes;2. excess heat denatures enzymes/alters tertiary structure/alters

shape of active site/enzyme;3. substrate cannot bind/eq,;4. reactions cease/slowed;5. too little reduces kinetic energy of molecules / molecules

move more slowly;6. fewer collisions/fewer ES complexes formed

Why more difficult to lose heat in humid conditionsreduced evaporation of sweat;due to reduced gradient / saturation /high water content of air;less heat loss by (latent) heat ofevaporation;

Bodys response to coldhypothalamus (contains thethermoregulatory centre);has receptors which detecttemperature changes of blood;receives impulses from receptors inskin;nerve impulses transmitted (fromhypothalamus / brain);

results in vasoconstriction /constriction of arterioles / dilation of


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shunt vessels;diversion of blood to core / specifiedorgan / less blood to skin;muscular contraction / shiveringgenerates heat via respiration;release of thyroxine / adrenaline;increase in metabolic rate /respiration;correct reference to negative feedbackmechanisms;

Insulinincrease in blood sugar, (more) insulinsecreted;binds to (specific) receptors on (liver /muscle) cells;leads to more glucose entering cells /

activates carrier proteins / opens proteinchannels / increased permeability toglucose;glucose leaves the blood;insulin activates enzymes (in liver);glucose entering cell converted to glycogen/ glycogenesis;

How a small increase in glucagon can cause a large rise in glucoseRef to cascade / amplification effect; 1>1 molecule of cyclic AMP formed per glucagon (molecule);each cyclic AMP activates >1 enzyme(molecule) ;

each enzyme causes breakdown of >1 glycogen (molecule);each glycogen gives >1 glucose / glycogen is a polymer;glucose diffuses into blood /glucose moves high to low concentration;

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How structure of DNA linked to functionsugar - phosphate backbone gives strength;(coiling gives) compact shape;sequence of bases allows information to be stored;

long molecule stores large amount of information;information can be replicated / complementary base pairing;(double helix protects) weak hydrogen bonds / double helix makes molecule stableprevents code being corrupted;chains held together by weak hydrogen bonds;chains can split for replication / transcription

Why DNA called semi conservativeNew molecule has one strand from parent molecule;and one new strand

Differences between tRNA and mRNAtRNA short chain versus mRNA long chainOR tRNA clover leaf shape versus MRNA straight chain


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OR tRNA folded versus mRNA straight;OR tRNA fixed length versus mRNA variable length

Role of tRNAanticodon complementary to codon / reads

message on mRNA;specific amino acid;carried / transferred (to ribosome);correct sequence of amino acids alongpolypeptide;

How mutation in DNA can cause faulty enzyme to be producedmutation;change in the sequence of nucleotides/bases/addition/deletion/substitution;Base sequence / codon (of DNA) is changed;Different (sequence of bases in) mRNA;

Attracts different tRNA / anticodon;changed order of amino acids/different protein/different tertiary;structure;inactive enzyme if shape of active site is changed/enzyme-substratecomplex does not form;

Mutagenic Agentshigh energy ionized particles/X-rays/ultraviolet light/high energyradiation/uranium/plutonium/gamma rays/tobacco tar/caffeine/pesticides/mustard gas/base analogues/free radicals;

How Protein is formedDNA uncoils/two strands separate/unzips;nucleotides of mRNA align with one strand;according to specific base pairing;RNA polymerase joins up nucleotides;mRNA moves out of nucleus through nuclear pore/into cytoplasm/attaches to ribosomes;tRNA takes specific amino acid to mRNA;anticodon of tRNA pairs with codon of mRNA/3 bases on tRNA pair with 3 bases on mRNA; peptide bond between amino acids;codons read sequentially/ribosome moves along mRNA;

tRNA collects another amino acid from cytoplasm;polypeptide/protein released from ribosome/polypeptide complete when stop codon reached;

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Stem Cellscells that can divide to form other types of cell/undifferentiated;Will replace themselves/keep dividing/replicate;

How stem cells differentiate


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cells are totipotent / can develop into anycell type;different genes expressed;related to relative concentration of growthregulators;different enzymes / proteins determinetissue formed;

siRNA molecules are:small / 2025 nucleotides;double-stranded (RNA);

Effect of siRNasingle siRNA strand;binds to mRNA;by complementary pairing;enzyme breaks down mRNA;

prevents transcription (of certaingenes);

Benefits of screening for cancer causing genesidentify those at risk of developing cancer;so as to avoid relevant environmentalfactors;enable early diagnosis;identify risk in families;

Malignant Tumourcell division by mitosis;tumour cells growth abnormal / continuous/ uncontrolled;tumour cells spread / invade other tissues /form secondary tumours / metastasis;via blood / lymph system;

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How to transfer human gene to plasmiduse of restriction endonuclease/enzyme;same for human and plasmid DNA;sticky ends;ligase used to insert/join human to plasmid DNA;

Why bacteria useful for producing insulin on large scalesimple nutritional requirements, so cheap to grow;can be grown on waste products from other processes,reducing costs;fast growth rate, so rapid increase in cells/product;can be grown aseptically, so avoiding harm to patients;can be grown under controlled environmental conditions,to get the best yield;

Why use bacteria in genetic engineeringEasy to insert genes into bacteria;


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Using a vector/plasmid/virus;Bacteria reproduce rapidly;Producing many copies of (inserted) gene;Bacteria can be grown on a large scale/ in industrial fermenters;To get a lot of the product of the gene;

PlasmidCircular loop of DNA;separate from main bacteria DNA;contains only a few genes;

Gene Therapyintroduction of healthy gene /replacement of defective gene

PCRHeat (DNA) to 95oC, to separate strands/break hydrogen bonds/denature;

Cool to 40oC, to allow primers/nucleotides to bind;Primers provide starting point for copying/prevent strands rejoining;Heat to 70oC, optimum for polymerase/enzyme;DNA polymerase then joins nucleotides together;

Role of primers in PCRenables replication / sequencing to start/ keeps strands separate;enclose area of DNA that is replicated;

Uses of PCRreplication of DNA from crime scene/ tissue sample / for DNA sequencing/ gene cloning

Vectormeans of getting new DNA into cell /host / gene carrier

Role of Restriction Endonucleasescut open plasmid;cut donor DNA, to remove gene /length of DNA;cut donor DNA and plasmid with the

same enzyme / enzyme that cuts at thesame base sequence;sticky ends / (overhanging) ends with,single strand / bases exposed;association / attachment / pairing ofcomplementary strand;

DNA ReplicationDNA strands separate / hydrogen bonds broken;Parent strand acts as a template / copied / semi-conservative replication;Nucleotides line up by complementary base pairing;Role of DNA polymerase;

DNA Fingerprinting


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1. DNA is cut;2. using restriction enzyme;3. use electrophoresis;4. separates according to length / mass;5. southern blotting / transfer to (nylon)membrane;6. make single-stranded;7. apply probe;8. radioactive / fluorescent;9. reference to tandem repeats / VNTRs /minisatellites;10. autoradiography (if radioactivity used);

Gene ProbeStrand of DNA;Short strand / up to 20 bases long;With base sequence that is complementary to part of target gene;

Radioactive labelling / fluorescent labelling;

What is meant by 6bp palindromic sequenceConsists of six antiparallel base pairs / six base pairs that read thesame in opposite directions;

Why deletion cause more disruption than substitutiondeletion causes frame shift / alters base sequence (from deletion);changes many amino acids / sequence of amino acids (from deletion);substitution alters one codon / triplet;one amino acid altered / code degenerate / same amino acid coded for;

How to make radioactively labelled strands visible after electrophoresistransfer onto nylon / filter sheet;X-ray / photographic film / (auto) radiography;

How genes are extracted and then inserted into bacteria1 (cut out gene using an) endonuclease / restriction enzyme; R. cuts gene2 reference to specificity / recognition site;3 sticky ends;4 use endonuclease / restriction enzyme (to cut plasmid/virus);5 plasmid/virus;

6 (spliced) by ligase;7 method of introducing vector e.g. micropipette / shock treatment // calcium chloride/ions / transformation / tungsten bullet;

How Science works

How to measure something under a microscopeMeasure with graticule/eyepiece scale;Calibrate against something of known size:OR

Estimate/measure field diameter with a scale;Estimate number of fibres to cover diameter;


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How to design an experimentHave control variables

Big range used for independent variable e.g. large range of concentrations used

Large samples

Random samples to avoid biasRepeats to make it more reliable, less likely to be due to human error in measuring

Valid method of measurement of dependant variable

Statistical tests to show significance

Describing a scatter graphWhats the correlationHow close are the points to the line of best fit

Evaluating dataIs there an overlap in ranges?What biotic and abiotic factors are there?What correlation is there?Correlation does not indicate a causal effect

Advantages of government agencies carrying out investigationsIndependent/ no biasNon-profit organisation

Documents

B4 and B5 model answers