Reuploaded Questions Flashcards
(162 cards)
1
Q
Suggest why some people with Huntington’s Disease may not want to take a blood test to detect the dominant allele (3)
A
Fear of needles Fear of positive result Fear of effect of result on other members of family No desire to have children Financial/insurance concernsPossibility of false resultsCost of testNot worth having test because of no treatment
2
Q
Explain how variation and natural selection may have brought about the evolution of the wooly mammoth from the steppe mammoth (5)
A
- Individuals varied in their phenotypes2. Caused by genetic variation/mutation3. Change in selection pressure/environmental conditions4. Idea that variation increases the chance of some individuals surviving 5. Explain adaptation i.e. Better insulation/greater surface area to volume 6. Survivors breed 7. Passed on alleles to offspring 8. Changed allele frequency in population
3
Q
Explain the likely effect of changing the amino acids in alpha and beta chains of haemoglobin (3)
A
Differences in primary structure Provides different side chainsChange in tertiary structureGreater effect on chains with more changed amino acidsChange in properties
4
Q
Suggest why it is advantageous for Arctic mammals to have haemoglobin whose affinity for oxygen is only slightly affected by changes in temperature (2)
A
Still able to offload oxygen in cold temperaturesSurface tissues colder than core temperatureSo can maintain oxygen supply to surface tissues
5
Q
Explain what is meant by the terms allele and dominant (2)
A
Allele - variation/different form of a geneDominant - allele always expresses itself in the phenotype when present
6
Q
Describe the consequences to a cell of these statements:1. Each cell only has a small quantity of ATP in it at any one time2. The molecules ATP, ADP or AMP rarely pass through the CSM
A
ATP is a source of energyATP broken down
7
Q
Explain the different yields of ATP from glycogen and palmitic acid (2)
A
Palmitic acid (a fatty acid) has more hydrogensPer mileHydrogens needed for ATP production/chemiosmosis/oxidative phosphorylation
8
Q
Describe when alanine and lactate are used as respiratory substrates (2)
A
Alanine = starvation/lack of carbohydrate or fat Lactate = after anaerobic respiration
9
Q
Name the organ that secretes LH
A
Anterior pituitary gland
10
Q
Describe the roles of LH in the menstrual cycle (3)
A
Stimulates follicleTo secrete oestrogenSurge in LH concentrationStimulates ovulationCorpus luteum develops/stimulates corpus luteum To secrete progesterone
11
Q
Suggest why researchers use two different methods to determine the phase of the menstrual cycle (2)
A
Ref reliabilityRef irregularity of cyclesIdea that cannot be sure about menstrual phase on day 22Idea that using hormones alone might not identify day of cycle precisely enough
12
Q
Explain why single-cross hybrids are genetically uniform but double-cross hybrids are not (3)
A
Single-cross hybrids have homozygous parentsEach has inherited the same allelesSo they are uniformly heterozygousDouble-cross hybrids have heterozygous parentsSo each has inherited different combinations of alleles, a mixture of homozygous dominant, homozygous recessive and heterozygous hybrids
13
Q
Explain how myelination affects the speed of conduction of impulses (3)
A
Myelin insulates axonNo myelin at nodesAction potentials/depolarisation only at Nodes of RanvierLocal circuits set up between nodes Action potentials ‘jump’ from node to node/salt story conductionMyelination prevents leakage of ions
14
Q
Suggest how myelin sheaths may be attacked (2)
A
Sheath treated as foreign/non-selfRole of antibodies/phagocytes/lymphocytes
15
Q
Explain why damage in myelin sheaths leads to a decrease in information reaching the brain from sensory receptors (2)
A
Less insulation of axonAction potentials slow down/stop
16
Q
Describe the role of accessory pigments in photophosphorylation (2)
A
Absorb light energyPass energy onto primary pigment
17
Q
Describe the reasons why an animal species can become endangered (4)
A
Direct human effect i.e. Hunting/fishing/collection/skinsHabitat destructionClimate change qualifiedIncrease in pollutionSpread in disease or new diseaseLack of foodIncreased predation
18
Q
Describe the reasons why a plant species can become endangered (4)
A
Direct human effect I.e. Specimen collecting/loggingHabitat destructionClimate change qualifiedIncrease in pollution Spread in disease or new diseaseLoss of pollinatorsIncreased competition from introduced plants
19
Q
Describe the reasons why an animal species can become endangered (4)
A
Direct human effect i.e. Hunting/fishing/collection/skinsHabitat destructionClimate change qualifiedIncrease in pollutionSpread in disease or new diseaseLack of foodIncreased predation
20
Q
Describe the reasons why a plant species can become endangered (4)
A
Direct human effect I.e. Specimen collecting/loggingHabitat destructionClimate change qualifiedIncrease in pollution Spread in disease or new diseaseLoss of pollinatorsIncreased competition from introduced plants
21
Q
Suggest reasons for changes in numbers of birds (4)
A
Decreases due to:Pesticides/pollution/fertilisersChange in temperature or pH of waterLack of named food sourceIncreased competitionDirect human interference on lake e.g. fishing/sailingIncrease due to:Doesn’t eat same food types as other birdsFewer other birds so less competition
22
Q
Explain the benefits of maintaining biodiversity (4) 🌟🌟IN BASICALLY EVERY PAPER🌟🌟
A
Cultural/aesthetic/leisure reasonsMoral/ethical reasons, e.g right to exist/prevent extinctionResource material e.g. Wood for building/fibres for clothes/food for humansEcotourismEconomic benefits Ref resource/species may have use in future e.g medical useMaintains food webs/chainsNutrient cycling/protection against erosionClimate stabilityMaintains large gene pool/genetic variation
23
Q
Describe the mode of action of penicillin on bacteria (3)
A
Penicillin inhibits enzymeBlocks shape of active sitePeptidoglycan chains cannot link up/stops cross-links formingCell wall weakerTurgor of cell not resisted by cell wallCell bursts
24
Q
Explain why penicillin does not affect viruses (2)
A
Viruses do not have cell wallViruses do not have cytoplasmViruses don’t have peptidoglycanViruses don’t have peptidase
25
Explain how a mutation of a gene coding for an enzyme may result in an enzyme with reduced activity (2)
Changed in base sequenceAlters triplet codeEnzyme has different primary structureEnzyme has different 3D structure
26
Explain the role of natural selection in the evolution of antibiotic resistance in bacteria (3)
Antibiotic is selective agent/provides selective pressureResistant bacteria survivePass allele for resistance to offspringFrequency of allele in population increases
27
State the roles of mitosis and meiosis in producing an immature secondary oocyte (3)
Germinal epithelial cell divides by mitosisGiving oogoniaPrimary oocyte divides by meiosis IDiploid to haploid
28
Describe how the liver reduces blood glucose concentration when insulin is secreted (3)
Binds to receptors in liver CSM Conversion of glucose to glycogen (glycogenesis)Insulin activates enzyme e.g. Glucokinase/phosphofructokinase/glycogen synthaseIncreased use of glucose in respirationIncreased uptake of glucose/increased permeability to glucose of liver cells
29
Suggest why isolating the mRNA coding for insulin in a beta cell is easier than isolating the DNA for insulin in a beta cell (2)
mRNA in a beta cell is only from gene coding for insulinLarge numbers of mRNA coding for insulinWhereas DNA has all genesSo restriction enzymes needed
30
Outline the use of restriction enzymes in preparing a plasmid vector (2)
Cut plasmid DNAat specific base sequenceLeaving sticky ends that will join with insulin gene
31
Suggest one advance and one disadvantage of inhaling insulin rather than injecting it (2)
Advantage:Faster response timeLess chance of infection/contaminationGood for people with needle phobia Disadvantage:Could cause larger swings in blood glucose concentrationMay need to take more oftenPossible variability of dose
32
Explain how the roots of rice plants being tolerant to ethanol helps them to survive when the fields are flooded (2)
Oxygen availability low Plants carry out anaerobic respirationEthanol producedRoots can continue to respire
33
Describe the function of the endosperm (2)
Store of nutrientsFor germination/growth of embryo
34
Explain why the grains of cereals such as rice are staple foods in many parts of the world (2)
Cheap source of foodHigh energy valueHigh in carbohydrateContain wide range of nutrientsCereal grains store wellBecause they contain very little water
35
Explain why populations of West African descent living in the USA have a decreased frequency of the HbS allele compared to West African populations (2)
Malaria not selection pressureHbS no advantageDue to outbreeding Genetic testing can lead to termination of pregnancy
36
Explain why side shoots increase in length when the terminal buds are removed (3)
Apical bud is source of auxinAuxin inhibits growth of side shootRemove bud and auxin conc fallsThis allows cell division/elongation to take place in side shoots
37
Outline the differences between cyclic and non-cyclic photophosphorylation (4)
Cyclic photophosphorylation:Electron emitted returns to PSINon-cyclic photophosphorylation:Electron emitted from PSII absorbed by PSI Reduced NADP producedPhotolysis occursPhotolysis only involves PSIIOxygen produced
38
Explain how synapses ensure one-way transmission of nerve impulses (2)
Vesicles found only in presynaptic neuroneReceptor proteins found only on postsynaptic membrane
39
Suggest the advantages of having an increased number of synapses (2)
Allows more interconnection of nerve pathwaysFor memoryAllows wider range of responsesAVP e.g. Summation
40
Outline how a gene from another species can be inserted into E.coli (3)
Gene isolatedInserted into plasmidCorrect ref. sticky endsPlasmid taken up by E. Coli bacteriumUse of restriction enzymes/cDNA produced
41
Explain how a marker gene, such as a gene for GFP, is used to show successful uptake of a gene for a wanted protein (3)
Marker gene linked to gene for wanted proteinWith promoterGFP gene is transcribedProducing GFP which fluroresces
42
Explain the meaning of the term self-pollination (2)
Transfer of pollen from anther to stigmaOn the same flower/plant
43
Explain why cross-pollination may be more beneficial to a species than self-pollination (3)
Idea of genetic variationIncreased heterozygosity Decreased inbreeding depressionable to adapt to changing conditions idea of some individuals surviving reduced risk of expression of harmful recessive alleles
44
Outline what is meant by the term ecosystem (2)
Biotic and abiotic componentscorrect ref to interaction 'All the living organisms of all species and all the non living components that are found together in a defined area and that interact with one another'
45
Suggest how human activities could damage coral reefs (3)
Named marine pollutant eg oil/sewageExample of climate change eg sea level rising/change in sea temperature/decrease in oxygen concentration of seaDecrease in pH of seaIntensive fishingTourism qualifiedRemoval of parts of reefReclaiming land
46
Explain why ATP is needed at the start of glycolysis (1)
Raise chemical PE of glucose/provide activation energy
47
State the role of NAD in glycolysis (1)
Removes hydrogen/hydrogen carrier/coenzyme
48
Describe what happens to the hydrogen released during the link reaction (2)
Accepted by NADPassed to ETCFor oxidative phosphorylationRef proton pump/chemiosmosis
49
Explain why ATP is regarded as the universal energy currency in organisms (5)
Immediate energy donorLoss of phosphate leads to energy release of 30.5kJ per mileSmall packets of energywater soluble so can move round cellImmediate energy donorLink between energy yielding and energy requiring reactionsHigh turnoverExample of use eg active transport
50
Explain how the principles of artificial selection would have been used to produce golden retrievers with the characteristics required for a guide dog (4)
Ideal characteristics selected by humansEg calm temperament/obedient/intelligentAllowed to mate/bred togetherOffspring with ideal characteristics chosen to mateOver many generationsAllele frequency increases Directional selection
51
State the role of reverse transcriptase in producing rDNA carrying the gene for human insulin (1)
Produces cDNA from mRNA
52
State the role of DNA polymerase in producing rDNA carrying the gene for human insulin (1)
Produces double stranded DNA from single stranded DNA
53
State the role of restriction enzymes in producing rDNA carrying the gene for human insulin (1)
Cuts DNA/plasmid
54
State the role of DNA ligase in producing rDNA carrying the gene for human insulin (1)
Joins gaps in sugar-phosphate backbone of DNA
55
Outline the role of insulin in a healthy human (3)
Causes blood glucose concentration to decrease or return to normal Target cells are liver/muscleIncreased absorption of glucose from the blood/permeability of cell-surface membrane to glucoseIncreased rate of respiration of glucose Increased conversion of glucose to glycogenInhibits secretion of glucagon/decreased gluconeogenesis
56
Describe and explain one advantage of treating diabetics of human insulin produced by rDNA technology (2)
Identical to that produced by bodyactivity the same/fast response/no immune responseno need for animal insulin for religious reasons/ethical reasons eg vegetarian uncontaminated/pure so no risk of disease production very efficient/always available Extraction from animals costly/complex/limited by supply of animals
57
Suggest how exchanging position of two amino acid is an insulin molecule can result in differences in activity (2)
Changes tertiary structureAffects binding to receptors on cell-surface membraneThis affects production of second messengerHydrophilic/hydrophobic bonds differentMay affect solubility in blood/transport in blood/rate at which broken down
58
List three reasons why it is important to conserve endangered plant species (3)
Maintains biodiversityMaintain genetic diversity/gene pool/gene variationLoss of a species may affect food chainsUse by humans eg medical use/building materials/food EcotourismEthical/moral/aesthetic reasons
59
Suggest explanations why a population could show a relatively low percentage of polymorphic bands (2)
Small number sampledSome alleles not included in the sampleMay be a small populationMay have developed form only a small number of original plantsSo only a small number of alleles present in the original population
60
Explain why high genetic diversity is important for a species (2)
Better chance of survival in changing conditionseg climatic/increased competition/new disease/new pestLess chance of two harmful recessive alleles coming together/inbreeding depression
61
Explain why storing seeds may be a more successful method of conservation than maintaining a population of growing plants (2)
seeds small and easier to storeSeeds can be stored for a long timeLittle maintenance requiredLess prone to disease/being eatenSeeds can be stored anywhere in the world
62
Suggest why a sample of each type of seed stored in a seed bank is germinated every few years (2)
To check that seeds are still viable/able to germinate To produce new plants from which fresh seeds can be collectedTo find conditions for breaking seed dormancy should plants be needed
63
State two ways in which the structure of ATP differs from the structure of an adenine nucleotide in a DNA molecule (2)
Contains ribose not deoxyriboseHas three phosphate groups not one
64
Explain why less ATP can be synthesised from the same mass of glucose in aerobic respiration than in anaerobic respiration (3)
Glucose not completely broken down - only glycolysis occursPyruvate/lactate/ethanol still contains energyETC stopsBecause no oxygen to act as final electron acceptorSo no Krebs cycle/link reaction/oxidative phosphorylation/chemiosmosis
65
Explain why more ATP can be synthesised in aerobic respiration from 1 g of lipid than from 1 g of glucose (3)
Lipid contains more hydrogen atomsMolecular formula of glucose and a lipid givenMore reduced NAD/FAD producedMore electrons passed along ETCMore hydrogen ions pumped across inner mitochondrial membrane
66
Outline the role of acetylcholinesterase (2)
Hydrolysed/breaks down AChStops continuous production of action potentials in post-synaptic neurone
67
Describe how CO2 reaches the inside of a palisade mesophyll cell from the external atmosphere (3)
Enters via stomataBy diffusion/down a concentration gradientPasses through air spacesDissolves in film of water on cell surfaceDiffuses through cell wall/CSM
68
The optimum pH for the activity of rubisco is pH8. Explain why the illumination of chloroplasts leads to optimum pH conditions for rubisco (3)
Excited electrons leave chlorophyll aPass along ETCProtons present from photolysis Protons pumped into intermembrane spaceRubisco is in stromaIdea that protons leaving stroma raises pH
69
Suggest ways in which the flatback turtle could be protected (5)
Avoid disturbance to nest sites/nesting femalesProtect nest sites from predatorsAvoid sea protectionExample of pollution eg do not throw rubbish into sea/avoid discharge from boats/light pollutionStop hunting of adultsCaptive breeding programmesConservation areas/zoosEducation/ecotourism
70
Describe how secondary spermatocytes are produced from spermatogonia in the process of spermatogenesis (4)
Spermatogonium divided by mitosisIncrease in sizeBecomes a primary spermatocyteMeiosis IForms secondary spermatocyte2n to n halving chromosome number
71
Outline how this leaf anatomy adapts the plant for high rates of carbon fixation and high temperatures (4)
Mesophyll cells tightly packedSo O2 cannot reach bundle sheath cellsLight dependent stage/Calvin Cycle or RuBP in bundle sheath cellsMalate shuntMaintains high CO2 concentration in bundle sheath cellsPEP carboxylase has high optimum temperature/has higher affinity for CO2 /doesn't accept O2Not denaturedPhotorespiration is avoided
72
Suggest how the wax on sorghum leaves helps the plant to survive in dry, tropical regions (2)
Reduces water lossWax does not meltShiny surface reflects radiation
73
Outline the process of oxidative phosphorylation (5)
Reduced NAD/FADDehydrogenase enzymesRelease hydrogenHydrogen splits into proton and electronElectrons flow down ETCEnergy releasedProtons pumped across inner membraneInto intermembrane spaceProton gradientProtons pass through ATP synthaseOxygen final proton acceptor
74
Explain why carbon dioxide is produced when mitochondria are incubated with pyruvate but not when they are incubated with glucose (3)
Glycolysis does not occur in mitochondrion/only occurs in cytoplasmPyruvate produced in glycolysis Pyruvate can enter mitochondrion but glucose can'tCarbon dioxide produced in Krebs cycle/link reaction
75
Explain why, in the presence of cyanide, lactate is produced but carbon dioxide is not (3)
Cyanide inhibits cytochrome oxidase/is a non-competitive inhibitorReduced NAD not oxidisedKrebs cycle stopsAlternative H acceptor needed/pyruvate is H acceptor Lactate produced in cytoplasmBy anaerobic respiration
76
Describe two ways in which CF affects the lungs (2)
Thick mucus producedMucus not moved effectively by cilia and accumulatesReduced gaseous exchangeDifficulty in breathingInfections/traps bacteriaLungs are scarred
77
Outline, with reference to CF, what is meant by gene therapy (2)
Alters genotypeInsert dominant alleleInto affected cellsUse of vector Ref recombinant DNA
78
Describe one possible advantage and one disadvantage of using gene therapy to treat CF. (2)
Advantage Treats cause not symptomsNo physiotherapy neededLess time consuming than other treatmentsDisadvantageEffects only last for a few days at presentOnly target lung cells at presentSide effects
79
Explain how the reaction catalysed by peroxidase in dip sticks results in the chromogen changing colour (2)
Catalyses breakdown of hydrogen peroxide to produce oxygen Chromogen oxidised by oxygenProduces range of coloursMore peroxide = greater change/darker colour
80
Explain why the estimate of glucose concentration achieved by dip sticks is only 'semi-quantitative' (2)
Only three colours for positive reactionsNo measurement of actual concentration/no numerical value measured
81
Suggest what is meant by the term 'renal threshold' (1)
The concentration of blood glucose above which some glucose appears in the urine
82
Outline the differences in the process of gametogenesis in a man compared to a woman (3)
Produces sperm or produces oocyteDivision of cytoplasm is equal or division of cytoplasm is unequalFour gametes produced or one gamete produced No polar bodies or polar bodiesMaturation stage or no equivalent maturation stageMeiosis completed or incomplete meiosis
83
Explain what is meant by an endocrine gland (2)
A ductless glandHormones in the bloodRef target organ/tissues
84
Explain how rice plants are adapted for growth with the roots submerged in water (3)
Low oxygen in water results in anaerobic respirationProduces alcoholRice tolerant to alcoholAs has high levels of alcohol dehydrogenasePresence of aerenchyma Allows oxygen to reach roots
85
Explain how an addition mutation could produce a stop triplet (2)
addition/insertion of a base to DNAChanges a sequence of 3 bases No longer codes for an amino acid
86
Suggest two ways in which the genome of the adenoviruses used as vectors would differ from that of normal adenoviruses (2)
Virus no longer able to cause infectionsCorrect allele addedPromoter added
87
Suggest why trials are first designed to include a small number of participants (2)
Ref to safety/not known if the technique might have side effectsCondition could be rareExpenseTrial to see if delivery method works
88
Explain why glucose needs to be converted to hexose bisphosphate (2)
Provides activation energyFor it to split
89
Describe what happens to pyruvate in a yeast cell when oxygen is not present (4)
DecarboxylaredEthanal produced Ethanal reducedBy reduced NADTo ethanolDehydrogenase
90
Many allergens that can trigger an asthma attack are inhaled during normal breathing. Suggest two examples of these allergens (2)
Cigarette smokeNames air pollutantAnimal fur/skin flakesPerfumes/aerosol/solventsDust/mitesPollen/spores
91
State one property of collagen that enables it to carry out its main function in the walls of blood vessels and airways (1)
High tensile strength Withstands pulling forcesFibrousInsolubleForms fibrilsFlexible
92
suggest the name of the type of enzyme that assembles the peptide chains that form the cross-links in peptidoglycans (1)
Peptidase
93
Suggest why Gram-positive bacteria are more susceptible to the action of penicillin than Gram-negative bacteria (2)
Penicillin can reach cell wall directly Outer membrane provides protection More % peptidoglycan in wall
94
Explain how sorghum is able to prevent photorespiration (4)
Ref bundle sheath cellsLight independent state occurs/RuBP found in BScellsRuBP kept away from air By mesophyll cells Limits uptake of O2/maintains high CO2 concentration in BScellsEnzymes/PEP carboxylase have high optimum temperatures45 degreesNot denatured
95
Suggest why a spermatozoa not contains so many mitochondria (2)
ATP productionFor movement of flagellumFor production of acrosomal enzymes
96
Suggest reasons why a man may be infertile (3)
Infectious disease causes damageLower sperm countDamaged spermBlocked sperm ductsNamed genetic condition eg CFAutoimmune reaction to spermReduced testosteroneEffect of chemical damage eg chemotherapy
97
Explain what is meant by the term in vitro fertilisation (2)
Fertilisation of oocyte by spermIn glass dishSperm injected into oocyte
98
Explain why there is a decrease in percentage of live births per treatment cycle with increasing age (3)
Ovulation less likelyOlder oocytes less likely to be fertilisedImplantation less likelyMiscarriage rate increasesLower concentration of hormonesGenetic defects increase with age
99
Describe the parts of the pancreas involved in its endocrine function (3)
Islets of langerhansScattered throughout pancreasAlpha and beta cellsBlood supply to carry hormones away
100
state precisely the group of compounds to which the pancreatic hormone insulin belongs (1)
Globular proteins
101
Describe the advantages of treating diabetics with insulin produced by gene technology (3)
It is identical to human insulin/fits membrane receptor on target cellsRapid responsefewer rejection problems/side effectsEthical/moral/religious issuesCheaper to produce in large volume/unlimited availability Less risk of transmitting diseaseGood for people who have developed tolerance to animal insulin
102
Describe the advantages of treating diabetics with insulin produced by gene technology (3)
It is identical to human insulin/fits membrane receptor on target cellsRapid responsefewer rejection problems/side effectsEthical/moral/religious issuesCheaper to produce in large volume/unlimited availability Less risk of transmitting diseaseGood for people who have developed tolerance to animal insulin
103
Lost four ways in which the structure of a dicotyledonous leaf is adapted for gas exchange (4)
StomataAir spaces between cellsThin cell wallsMost internal wallsThin leadCylindrical palisade cellsLarge surface area of palisade cells
104
Explain the role of coenzymes in this leaf cell, with respect to the metabolic reactions of a plant cell (3)
NAD/FAD/NADP can accept hydrogenReduced NAD supplies electrons to the electron transport chainReduced NAD supplies hydrogen ions for chemiosmosisReduced NADP supplies hydrogen to light independent stageCoenzyme A carries acetate to Krebs cycle
105
Define bioinformatics
The collection, processing and analysis of biological information and data using computer software
106
Explain the advantages of the use of monoclonal antibodies compared with conventional methods in the diagnosis of disease (3)
Quick diagnosisThan having to culture pathogenSo quicker treatmentLess labour intensiveNot all pathogens can be culturedMicroscopic identification difficultViruses difficult to identifyRef specificity/non-pathogenic diseases
107
Explain how, in the process of genetic fingerprinting, gel electrophoresis is able to distinguish between the VNTRs that occur at the same loci of different individuals (3)
VNTRs with more repeats are longer Phosphate groups of DNA give negative chargeFragments attracted to anodeShorter pieces move further in unit time Ref impedance of gel
108
Describe the different circumstances in which this genetic screening for the sickle cell allele HbS might be used (3)
To identifyA carrier before marriageA carrier before conceiving HbS HbS child in uterine re terminationHbS HbS child at birth re treatment Ref genetic counselling
109
Outline the role of progesterone in the human menstrual cycle (3)
Mostly secreted during the second half of the cycle/day 14 onwardsMaintains lining of the uterusIn preparation for implantationInhibits GnRH/development of new follicle
110
Explain the meaning of the term biodiversity (1)
Diversity of ecosystems in a regionThe number of different species in each ecosystemThe genetic diversity within populations of each species
111
Suggest and explain why the rate of photosynthesis of the plant decreases to zero just above 40 degrees (5)
26 degrees optimum temperature for rubiscoAt just over 40 degrees enzymes denatured So less carbon dioxide fixedReduction in Calvin cycleIncreased rate of transpirationSo stomata closeLess carbon dioxide uptakeOxygen more likely to combine with rubiscoSo increased photorespiration
112
With reference to photosynthesis state what is meant by a limiting factor (2)
When a process is affected by more than one factorThe rate of photosynthesis is restricted by the factor that is nearest its lowest value
113
200 small freshwater crustaceans were released into a pond where there had previously been none. The pond was favourable for their growth and reproduction. Describe and explain the expected changes in their population size over the following few months (5)
Population increases slowly at first/lag phaseBecause adjusting to pond environment Then steep increase/log phase/exponential increaseBecause abundant food sourceStationary phaseFall in population size/death phase/decline phaseDue to predation/build up of waste Competition for named resource eg food shortageIdea of further rise and fall/population size may be cyclic
114
Explain why variation is important in natural selection (2)
Variation means the presence of different characteristicsResulting in different survival rates Leads to reproductive success/failure
115
Describe how cells of B.subtilis could be immobilised in beads of align are (3)
Bacteria out into sodium alignate solutionPlace mixture in syringeAdd drops of mixture to calcium chloride solutionCalcium ions replace sodium ions to form beadsBacteria trapped in beads
116
Suggest why lower concentrations of protease were produced by B.subtilis immobilised in agar cubes than B.subtilis immobilised in alginate beads (2)
Could be less surface area to volume ratio in cubes than beadsCould be a greater diffusion distance to centre of cubes than beadsAgar may be less permeable to substrate than alginateSomething in agar may inhibit bacterial enzymesSome protease adsorbed by agar
117
How does environment affect phenotype? (8)
Phenotype varies due to genotype and environmentEnvironment may modify expression of genesEg size/mass/heightLack of food/nutrient/ion and example ie vitamin a Environment may switch genes onLow temp = colour changeHigh temp = drosophila curl wingUV light = melanin productionWavelength of light -> flower germinates + fruit colourEnvironment has a greater effect on polygenesEnvironment has an effect on mutation
118
Explain why the volume of oxygen released from the plant does not give a true rate of photosynthesis (1)
Respiration uses oxygen
119
Explain why genes for fluorescent proteins are now more commonly used as markers than are genes for antibiotic resistance in gene technology (2)
Easier to identify/screenMore economical Resistance genes can be passed onto other bacteria Idea of antibiotics no longer effective/requiring development of new antibiotics
120
Explain why in gene technology a promoter needs to be included when transferring a gene from a coral to an insect (3)
Promoter initiates transcriptionRef binding of RNA polymerase/transcription factorsOtherwise gene has to be inserted near existing promoterThis is difficult to do/might disrupt expression of existing geneIn eukaryotes precise position of promoter importantIdea that you need a coral promoter to switch on a coral gene
121
Outline the principles of gel electrophoresis (4)
DNA fragmented by restriction enzymesLoaded into wells at negative end/cathode endRef buffer/electrolytePhosphate groups of DNA give negative chargeNegatively charged DNA attracted to anode/positive electrode Separation due to electric field Short pieces move further in unit timeref impedance of gel
122
Explain how the presence of a gene can be confirmed once electrophoresis is complete (2)
Idea of comparison of position with reference DNARef staining/fluorescence in UVBy use of DNA probeRef single stranded/complementary base pairing
123
Suggest why it is important to be sure whether a moth caught in such a trap is a released sterile male or a wild insect (2)
Allows estimation of numbers of each type To check success of release of sterile malesIf sterile males wrongly identified as wildThere will be a waste of resources eg pesticidesIf wild males wrongly identified as sterile malesA potential infestation may be missedTo determine which moths to rerelease
124
Suggest what information would be needed to determine whether the release of the sterile male moths, carrying a gene called DsRed, has a damaging effect on the environment (2)
That DsRed is not toxic to predators of the mothThat DsRed does not persist in the environmentThat the gene cannot pass to other organismsdoes not alter food web/ecosystem
125
Explain what is meant by the term continuous culture (2)
Nutrients added and product removed at a steady rateSo volume kept constantOrganism kept at exponential/log phase of growth
126
Describe briefly where the electrons that are passed along the electron transport chain come from (3)
HydrogenFrom reduced NAD/FADFrom dehydrogenation reactionsFrom substances in Krebs Cycle/link reaction/glycolysis In matrix of mitochondrion/cytoplasm
127
Describe the role of oxygen in the process of oxidative phosphorylation (2)
Final electron acceptor/accepts electron from last carrierSo carrier can be reduced againSo electrons can keep flowing along ETCOxygen combines with H+ to form water
128
Explain why the membrane of the neurone depolarises when the Na+/K+ pump stops working (4)
When pump stops working resting potential not maintainedDuring resting potential membrane polarised When pump stops working ions only move by diffusionNa+ into neurone Outward diffusion of K+ limited/K+ stays inside neuroneRef non voltage-gated channelsEventually inside of neurone becomes less negative/contains mor expositor ions
129
Suggest why calcium ions flood into the neurone when the Na+/K+ pump stops working (2)
Voltage gated channels openCalcium ions move in by diffusion
130
Explain how the structures of the glomerular capillaries and the podocytes are adapted for ultrafiltration (4)
Fluid can pass through glomerular capillaries because:Fenestrations in capillary endotheliumBasement membrane acts as a filterNo substances >68 000 MM can get through No cells can get throughFluid can pass through podocytes because:Have projectionsGaps between projections
131
Explain why the epithelial cells of the PCT have many mitochondria in them (2)
Produce ATP for active transport of Na+Out of cell
132
Name two substances reabsorbed into the blood from the PCT apart from water (2)
VitaminsAmino acidsGlucosesome urea
133
Explain how a single base substitution may affect the phenotype of an organism (3)
Different codon/tripletStop codonDifferent amino acidDifferent primary structureShortened polypeptideChange in function of protein
134
Suggest two reasons why the population of crocodiles in the Everglades National Park has increased (2)
Ensure low salinity/more fresh waterBest sites protectedEducation/ecotourismAssisted breedingBan on huntingPreventing pollution
135
Explain why FSH does not bind to a LH receptor (3)
Receptor not complementary/specific to FSHFSH has shorter beta chain than LHFSH has different primary structureFSH has different tertiary structure
136
Name the cells of a human female that carry FSH receptors and LH receptors (2)
FSH - follicle cellsLH - corpus luteal cells
137
Describe what happens when FSH binds to its receptors on its target cells (3)
Acts as a signal to the cellTo start synthesis of hormoneOestrogen secretedStimulates thickening of endometrium/ inhibits FSH production
138
Distinguish between batch culture and continuous culture of microorganisms (3)
Batch culture:Set up and allowed to proceedNutrients not added or products removed during fermentationAir allowed in/waste gas allowed outAt end of each process product harvested/fermented cleaned outContinuous culture:Nutrients added all the timeProducts removed all the timeNo down time
139
Explain why batch culture rather than continuous culture is used in the production of penicillin (3)
Fungus does not make penicillin all the time/penicillin is made in the later stages of growthWhen beginning to run out of nutrientsPenicillin is a secondary metaboliteContinuous culture has no yield of penicillinContinuous culture never reaches stationary phase of growth/always exponential growth
140
Explain why cereal crops are important components of many peoples diets (3)
Can be grown in many different environmentsGrains contain variety of nutrientsDetail of nutrient content eg high in calcium/vitamin B/protein Grains have high energy/fibre contentGrains store well
141
Suggest why there is more divergence in some regions of DNA than others (2)
Some regions of DNA more prone to mutation than othersMutation in some regions likely or be fatalThere tends to be less divergence if DNA is part of an important geneEg causes change in essential protein
142
Explain what is meant by the term sex linkage (2)
Allele found on X chromosomeFemales have two copies of alleleMales have only one copy of allele
143
Describe be role of reduced NAD in respiring yeast cells in the absence of oxygen (4)
Pyruvate converted to ethanalEthanal reducedBy reduced NADNAD oxidised/regeneratedAllows glycolysis to continueEthanal dehydrogenaseEthanol formedPrevents H+ from lowering pH
144
Describe how the production of lactate in muscle tissue differs from anaerobic respiration in yeast (3)
No decarboxylaionSingle stepLactate dehydrogenaseReversible
145
Outline what is meant by gene technology (2)
Change in geneticMaterialTherefore change product of cellDuring protein synthesis
146
Explain why genes for enzymes that produce fluorescent substances are used as markers in gene technology (2)
Identification of transformed cellsavoid use of antibioticsEasy to detectNo known ill effect on GM organism
147
Suggest two advantages of growing GM rice won't an enhanced vitamin A content (2)
Reduces deficiency diseaseBetter quality foodCheep seed eg for Golden riceAssistance to developing nations
148
Suggest two disadvantages of growing GM crops (2)
High cost of GM seedToo much power held by multinational companiesChanges to ecosystem eg hybridisation GM crops may be difficult to sellGM plant varieties may be genetically unstableNo long term studies done on effects on human healthReduction in biodiversity/out competes natural variety or species
149
Explain what is meant by the term photosynthetic pigment (3)
Light absorbingRef to excited electronsUsed in light dependent stageRef to location eg chloroplasts, thylakoidsPhotosystems, grana, lamellae Long hydrocarbon chains Different pigments absorb different wavelengths
150
Explain the difference between primary and accessory pigments (2)
Primary act as reaction centres/where electrons are excitedAccessory other part of Photosystem/antenna unit/surround reaction centreAccessory absorb different wavelengths of light not absorbed by primaryAccessory pigments transfer energy to primary pigmentsPrimary pigments chlorophyll a/P680/P700 and accessory pigment chlorophyll b/carotenoids
151
Explain what is meant by the term photosynthetic pigment (3)
Light absorbingRef to excited electronsUsed in light dependent stageRef to location eg chloroplasts, thylakoidsPhotosystems, grana, lamellae Long hydrocarbon chains Different pigments absorb different wavelengths
152
Explain the difference between primary and accessory pigments (2)
Primary act as reaction centres/where electrons are excitedAccessory other part of Photosystem/antenna unit/surround reaction centreAccessory absorb different wavelengths of light not absorbed by primaryAccessory pigments transfer energy to primary pigmentsPrimary pigments chlorophyll a/P680/P700 and accessory pigment chlorophyll b/carotenoids
153
Describe how light is harvested in the chloroplast membranes (5)
Pigments are in photosystem/complex/antenna complexPhoton/light energy absorbed by pigment moleculesElectron excited and returned to pigment Energy passed from one pigment to another Passed to reaction centre Range of accessory pigments allow range of wavelengths to be absorbed
154
Suggest the role of DNA and ribosomes in chloroplasts (2)
DNA coding for genes/proteins/enzyme or ribosome protein/enzyme synthesis Enzymes for production of/proteins for chlorophyll synthesis/pigment synthesis/photosystemProtein for electron acceptors/carriersATP synthase Enzyme for photolysisEnzymes for Calvin cycle/light dependent reaction
155
Describe how an action potential is transmitted along a sensory neurone in a mammal (5)
Action potential stimulates neighbouring area of membraneNa+ moves sideways/attracted to areas at resting potentialCauses Na+ channels to openTransmutation in one direction due to hyperpolarisation/refractory periodMyelin sheath/Schwann cellSheath insulates axonDepolarisation only at nodes of RanvierSaltatory conduction
156
Suggest the functions of the DNA and ribosomes in a mitochondrion (3)
DNA for transcriptionRibosomes for translationSynthesis of respiratory enzymes/inner membrane proteins
157
Explain what is meant by heterotrophic (2)
Idea of feeding on other organisms
| To obtain organic compounds
158
Explain what is meant by the terms gene mutation and triplet code (4)
Gene mutation:
Spontaneous/random change
In base sequence
Eg addition/insertion etc
Triplet code:
Sequence of three bases
Complementary to mRNA codon
Codes for a specific amino acid
159
Explain what is meant by heterotrophic (2)
Idea of feeding on other organisms
| To obtain organic compounds
160
Explain what is meant by the terms gene mutation and triplet code (4)
Gene mutation:
Spontaneous/random change
In base sequence
Eg addition/insertion etc
Triplet code:
Sequence of three bases
Complementary to mRNA codon
Codes for a specific amino acid
161
Explain what is meant by heterotrophic (2)
Idea of feeding on other organisms
| To obtain organic compounds
162
Explain what is meant by the terms gene mutation and triplet code (4)
Gene mutation:
Spontaneous/random change
In base sequence
Eg addition/insertion etc
Triplet code:
Sequence of three bases
Complementary to mRNA codon
Codes for a specific amino acid
