Past PaperQs

Question 1

Describe and explain How the structures in the bowman’s capsule and its associated blood supply are adapted to allow ultrafiltration to take place

(9700/42/o/n/21)

Answer 1

Afferent and Efferent Arteriole have diffrent diameters controlling blood pressure in the glomerulus

Gaps between the capillary endothelium cells, podocytes and basement membranes acts as filters preventing RBC and other large components from entering the nephron

Question 2

Intermediate products of the Calvin cycle are needed to produce organic molecules for use by the cell
Describe how these organic molecules are used by cells

(9700/42/o/n/21)

Answer 2

Glucose is used for Generating ATP as its the currency for energy needed in important processes
Celluse is used to build up the cell wall of the plant
Sucrose for translocation in the phloem and stores as fructose or starch

Question 3

Describe the sequence of events that lead to the production of amylase during seed germination

(9700/42/o/n/21)

Answer 3

When water enters the cell the embryo produces gibberellins which to the aleurone layer
Della protein blocking the receptors is destroyed by the gibberellins
Pif binds to the receptors
Amylase gene is expressed by the RNA polymerase
and amylase is produced

Question 4

Explain the relationship between the absorption spectrum of the main chloroplast pigments in a species of plant and the action spectrum for photosynthesis for this species

(9700/42/o/n/21)

Answer 4

Action spectrum shows the rate of photosynthesis in wavelengths
Absorption spectrum shows how each wavelength is absorbed
Higher absorption results in higher photosynthesis

Question 5

explain why temperature can be a limiting factor of photosynthesis

(9700/42/o/n/21)

Answer 5

As temperature increases the rate of photosynthesis also increases allowing more ESC forming and more product forms
in Light dependent (Photophosphorylation) reactions But if the temperature exceeds the optimum enzymes denature and ESC decrease and photosynthesis is slower

Question 6

Outline how the light independent stages of photosynthesis leads to the production of carbohydrates such as starch in plants
(Calvin cycle)

(9700/42/o/n/21)

Answer 6

RuBP(5C) carboxylate by RUISCO (enzyme) Forms an unstable 6C compound

C-C broken to form Glycerate phosphate/Phosphor glycerate
(Fatty acids and glycerol for phospholipids and triglycerides)

NADR–>NADP producing ATP

results triose phosphate which is an organic molecule (3C) can form hexose sugar (Starch, cellulose, sucrose)

ATP–>ADP+P back to RuBP (5C)

Question 7

Explain why why the inner membrane of a mitochondria remains intact when the organelle is placed in pure water

(9700/42/o/n/21)

Answer 7

The inner membrane (Cristea) Expands as it creates a H+ gradient out the matrix
When water enters by osmosis

Question 8

Name three molecules other than coenzymes, that are found in the mitochondrial matrix and explain their role in aerobic respiration

(9700/42/o/n/21)

Answer 8

Pyruvate Used for Link reaction It binds to CoA which plays the Krebs cycle

Oxoacetate accepts acetyl making citrate

Oxygen accepts electrons to form water

DNA/RNA to make respiration enzyme

Enzymes to catalyze reaction reaction in link reaction and Krebs cycle

Question 9

Name Chloroplast pigment

(9700/42/o/n/21)

Answer 9

Chrolorophyll a
Chrolorophyll b
Beta carotene

Question 10

Suggest the advantages of linking ATP transport to ADP transport across the inner membrane of the mitochondrion

(9700/42/o/n/21)

Answer 10

Constant supply of ADP
ATP can continue to be made

Question 11

Describe and explain the action of ADH on the cells of the collecting duct when the water potential of the blood decreases

(9700/42/o/n/21)

Answer 11

ADH binds to cell, surface / membrane, receptor (of collecting duct cells)
G protein is stimulated to activate adenylate cyclase
Secondary Messager CAMP starts a cascade reaction until the inactive glycogen phosphorylase
The needed enzymes are active (Protein kinase)
Vesicles with aquaporin move towards the phospholipid bilayer to fuse with it
Collecting duct is permeable to water

Question 12

Describe how the expression of the TYR gene leads to the production of melanin

(9700/42/o/n/21)

Answer 12

TYR codes for tyrosinase
converts tyrosine into DOPA
converts DOPA into dopaquinone
dopaquinone converted to melanin

Question 13

Outline how yeast carries out respiration in anaerobic conditions

(9700/42/o/n/21)

Answer 13

glycolysis ;
glucose to pyruvate ;
pyruvate to ethanal by, decarboxylation / CO2 removal ;
ethanal, reduced / hydrogenated, to ethanol ;
reduced NAD to NAD ; A regeneration of NAD
AVP ; e.g. ethanol / alcohol, dehydrogenase or pyruvate decarboxylase

Question 14

Explain why respiration in anaerobic conditions is an advantage to yeast

(9700/42/o/n/21)

Answer 14

can survive (in absence of oxygen) ;
(as) ATP still produced (from glycolysis) ;
glycolysis can continue ;
as NAD recycled ;

Question 15

Explain how grana are adapted for their specific role in photosynthesis

(9700/42/o/n/21)

Answer 15

thylakoid stacks or discs / many thylakoids, for, increased or large, surface area ;
maximizes the absorption of light
photosynthetic pigments to absorb light (energy) ;
ETC, to, transfer (from excited electrons) ;
photosystems reaction Centre, are light harvesting structures ;
thylakoid space or lumen to, have high concentration of protons ;
thylakoid membrane is (relatively) impermeable, to maintain the proton gradient (for chemiosmosis) ;
ATP synthase to make ATP ;
Contains oxygen-evolving complex / OEC, for the photolysis of water ;

Question 16

Explain why a promotor has to be introduced as well as desired gene

(9700/42/o/n/21)

Answer 16

to allow binding of, RNA polymerase to switch gene on allow transcription (of gene)
at right time in sufficient quantities ;
in correct tissue ;

Question 17

Suggest why structural gene in operons are transcribed together

(9700/42/o/n/21)

Answer 17

One promotor
All enzymes work together

Question 18

Describe the difference between the functions of structural

(9700/42/o/n/21)

Answer 18

structural genes:
code for, enzymes / structural proteins / non-regulatory proteins / rRNA / tRNA ;

regulatory genes:
code for, proteins / products, that control, gene expression / transcription ;

Question 19

Explain why tryptophan synthase is an example of a repressible enzyme

(9700/42/o/n/21)

Answer 19

end-product inhibition 
tryptophan, binds to repressor
or
tryptophan allows repressor to bind to operator ;
tryptophan, stops / reduces, trpA or gene transcription

Question 20

A survey taken in 2017 showed that 60% of the hedgehogs on Alderney had blonde spines.
Suggest and explain reasons why the proportion of hedgehogs with blonde spines was so high.

(9700/42/o/n/21)

Answer 20

directional selection ;
blonde spines have a selective advantage / described

allele frequency for blonde spines increases / increased homozygosity (for recessive or blonde allele)

inbreeding

small gene pool (at start) / little genetic variation

founder effect / genetic drift / bottleneck effect

Question 21

Suggest and explain why preventing the free movement of mitochondria within the
cytoplasm of the axon affects the transmission of action potentials along the axon
membrane.

(9700/42/f/m/22)

Answer 21

no / less, ATP for the, sodium-potassium pump / active transport of Na+ and K+ ;
2 reduces / prevents, (re-establishment of) resting potential ;
3 reduces transmission of action potential (along the axon) ;

Question 22

Walking requires nervous control to coordinate movements. One of the first signs of GAN is having problems with walking.

Explain how the speed of transmission of nerve impulses in people with GAN can affect walking.

9700/42/f/m/22

Answer 22

takes longer for impulses to reach, neuromuscular junction / muscles ;
2 fewer / slower, muscle contractions ;
3 walking problem described ; e.g. reduced muscle control / walks slower / stumbles / trips
4 slower reflexes ;

Question 23

Define ecosystem

(9700/41/m/j/23)

Answer 23

A community of different organisms and their interactions with abiotic and biotic factors

Question 24

Define niche

Answer 24

Role of a species within its ecosystem

Question 25

Biodiversity can be assessed at a number of different levels. Identify the levels of biodiversity: * that were assessed by this sampling technique * that were not assessed by this sampling technique.

Answer 25

were assessed: abundance of (selected) species not assessed: range of (different) ecosystems / habitats genetic variation

Question 26

Seaweeds were once thought to be plants but are now classified in the kingdom Protoctista. Outline the features of the kingdom Protoctista that are shown by seaweeds.

Answer 26

eukaryotic (cells) autotrophic / photosynthetic cellulose cell wall aquatic not motile / sessile multicellular no, vascular tissue / xylem / phloem

Question 27

state the function of aerenchyma

Answer 27

supplies oxygen to the cells underwater during aerobic respiration

Question 28

Auxin is a plant growth hormone that affects the growth of rice stems. Explain how auxin affects the growth of rice stems.

Answer 28

Increases stem length when protons are pumped into the cell wall Expansins break hydrogen bonds between cellulose microfibrils Water enters the cell by osmosis and they elongate

Question 29

Name the structure that converts ATP to AMP to activate protein kinase in cell signally

Answer 29

Adenyl cyclase

Question 30

Describe how blood is filtered by the part of the kidney nephron

Answer 30

ultrafiltration high pressure due to afferent arteriole wider than efferent arteriole capillary endothelium has gaps ions, glucose, amino acids, urea and water leave the blood basement membrane forms selective, barrier podocytes support basement membrane

Question 31

Neurones need to maintain a resting potential before an action potential can occur. Describe how a neuron maintains a resting potential.

Answer 31

sodium-potassium pump 3Na+ out and 2K+ inside of axon is more negative (than outside) outside of, axon is more positive (than inside)

Question 32

Explain how the behavior of the chromosomes in prophase I of meiosis

Answer 32

DNA condenses and forms into sister chromatids Homologous chromosomes pair up Crossing-over between non-sister chromatids ; chromosomes (stay) joined at chiasmata

Question 33

Coenzymes are important in aerobic respiration. Outline the roles of named coenzymes in aerobic respiration.

Answer 33

Binds to acetyl group acetyl CoA + oxaloacetate -->citrate (joins) link reaction and Krebs cycle NAD and FAD reduced by hydrogen (atoms) Transport for oxidative phosphorylation NAD (accepts H) in glycolysis and link reaction and Krebs cycle

Question 34

Sweet peas are garden plants that vary in height. * Tall sweet peas grow to 200cm in height. * Dwarf sweet peas grow to 30cm in height. * Tall sweet peas contain a dominant Le allele. * Dwarf sweet peas are homozygous for the recessive le allele. Explain how the lele genotype results in the dwarf phenotype in sweet peas, with reference to the effect of lele on: * enzyme synthesis * hormone production * the expression of genes affecting plant growth.

Answer 34

le allele codes for a, non / less, functional enzyme ; Inactive gibberellin not converted to active gibberellin So less, gibberellin-receptor-DELLA complexes formed ; DELLA not broken down ; DELLA (stays) bound to, transcription factors ( PIF ) Transcription factor (PIF) cannot bind to promoter ; XET gene (growth gene) switched off / not transcribed / not expressed Stem does not elongate

Question 35

In anaerobic conditions, no ATP can be synthesised by oxidative phosphorylation because the process stops. Explain why ATP synthesis by oxidative phosphorylation stops in anaerobic conditions (9700/41/m/j/24)

Answer 35

oxygen, the final electron acceptor is absent electron transport chain (ETC) stops no H+ move into intermembrane space no electrochemical, gradient no protons move through ATP synthase no regeneration of NAD / FAD

Question 36

Up to 60% of the ATP that is produced in cancer cells comes from lactate fermentation of glucose, even though oxygen is present. Scientists are developing cancer treatments to inhibit the enzyme that catalyses the last step of lactate fermentation. Explain how the inhibition of this enzyme reduces the production of ATP in cancer cells.

Answer 36

Lactate dehydrogenase inhabited no, pyruvate → lactate ; no, NAD, regenerated no ATP

Question 37

Coordination in humans involves two main systems: the nervous system and the endocrine system. Paracrine cell signalling is a third way in which coordination occurs. In paracrine signalling, one cell secretes a chemical that diffuses a short distance to act upon cells that are very near to the secreting cell. Identify one similarity and one difference between paracrine cell signalling and cell signalling that occurs as part of the endocrine system.

Answer 37

Similarity: both involve a (signalling) ligand Difference: endocrine chemical (hormone) travels by circulatory system (but paracrine chemical travels short distances by diffusion )

Question 38

Stomata in leaves respond to changes in environmental conditions by opening and closing. This regulates carbon dioxide uptake and water loss. Describe the mechanism by which stomata open in sunlight.

Answer 38

H+ ions, pumped, into guard cells negative potential (inside cell) or Cl – ions enter (cell) ; (voltage-gated) K+ channels open water enters cell, by osmosis (guard) cells become turgid increase in volume

Question 39

The process of protein translation is inhibited in developing muscle cells when stress genes are expressed. Suggest how developing muscle cells that express stress genes will differ in structure from normal muscle cells.

Answer 39

less actin less myosin less troponin less tropomyosin smaller sarcomeres / myofibrils /myofilaments / mitochondria / ribosomes ;

Question 40

Suggest how the researchers were able to discover suitable sequences for the primers

Answer 40

Using bio informatics

Question 41

Suggest 2 ways in which new fruit color could naturally occur in a sea blush population | (9700/42/m/j/23)

Answer 41

mutation formation of a new allele ; change in, environment / selection pressure ; cross pollination / cross breeding / hybridization ; new allele combination / codominant alleles together

Question 42

Early taxonomists classified sea blush plants with winged fruits as a different species to sea blush plants with wingless fruits. Since this time, evidence from observations and experiments has confirmed that the plants belong to the same species. Suggest three examples of the evidence obtained that helped to confirm that these sea blush plants belong to the same species. | (9700/42/m/j/23)

Answer 42

(inter)breed to produce fertile offspring / not reproductively isolated ; occupy the same niche ; same / similar, morphology / physiology / biochemistry ; have, similar / same, genes / DNA sequences / genomes ; similar / same, proteins / amino acid sequences ;

Question 43

Explain why natural selection occurs in populations. | (9700/42/m/j/23)

Answer 43

(populations) can produce many offspring genetic variation occurs (in populations) mutations / sexual reproduction / gamete formation / random fertilization ; competition qualified ; e.g. mates / food / resources selection pressure ; some individuals have advantageous, adaptations / phenotype / traits / AW ; (so) they, survive / reproduce / have a selective advantage ; (so) pass on their advantageous allele(s) ; (so) the (advantageous) allele frequency increases ;

Question 44

Outline the two methods for synthesizing a gene for use in genetic engineering. | (9700/41/o/n/24)

Answer 44

make cDNA from, messenger RNA / mRNA ; 2 using reverse transcriptase ; 3 synthesise (gene chemically) from nucleotides / join nucleotides ; 4 (using known) amino acid / nucleotide, sequence from database ;

Question 45

The polymerase chain reaction (PCR) is used to make many copies of a gene. Three temperatures are used in a PCR cycle. State the three temperatures that are used, and outline what happens at each temperature during a PCR cycle. | (9700/41/o/n/24)

Question 46

The rat motor neuron has an impulse transmission speed of 50ms –1 The snail motor neuron has an impulse transmission speed of 8ms–1 Explain why the rat motor neuron has a faster impulse transmission speed than the snail motor neuron | (9700/41/o/n/24)

Answer 46

rat has, myelin sheath / Schwann cell / myelinated axon / myelinated neuron ; (rat has) saltatory conduction OR (rat) impulse / action potential, jumps / leaps / AW, from (one) node of Ranvier to, the next / another ;

Question 47

The cells of the proximal convoluted tubule are adapted to carry out selective reabsorption. Describe and explain how these cells are adapted to carry out selective reabsorption | (9700/42/f/m/24)

Answer 47

microvilli, for large surface area / increases surface area (for reabsorption) ; cotransporter (proteins) for movement of, glucose / amino acids (with sodium ions) ; tight junctions / described, to, stop substances passing in between cells / cause substances to pass though cells ; many mitochondria to provide ATP for, active transport / pumping of Na+ folded basal membrane for many sodium (potassium) pumps ;

Question 48

Discuss the ethical and social considerations of making a genetic test for cystic fibrosis available to these adults | (9700/42/f/m/24)

Answer 48

reduces worry if result is negative can make informed reproductive decisions cost / availability, of test ; plan for care of child with CF ; idea of further genetic testing ; e.g. counselling / testing of embryo / testing of partners idea that test is not 100% accurate ; problems related to, stigma / discrimination/ insurance/ confidentiality ;

Question 49

Suggest reasons why immunofluorescence tagging is NOT a suitable choice for this investigation | (9700/41/m/j/20)

Answer 49

Antibodies are too big to enter cells Monoclonal antibodies is a large process and more expensive where it can harm animals Immunofluorescence is only used on dead cells

Question 50

Describe and explain characteristics of mtDNA that makes it more useful than using nuclear DNA to provide evidence of evolution | (9700/42/m/j/20)

Answer 50

Large quantity in the cell ; so easier to, extract / amplify, DNA for testing ; small genome size ; so easier to locate specific section of DNA to test ; mtDNA is, a single copy of DNA / not paired alleles / haploid ; so only mutation causes it to change ; inherited maternally ; so all mtDNA sections are shared between all members (of maternal) family ; mutation rate is higher / no enzymes to repair mutations / faster molecular clock ; so more choice of suitable sections of mtDNA to test / more accurate time estimate ;

Question 51

suggest reasons why a species became extinct | (9700/42/m/j/20)

Answer 51

habitat loss ; more competition for, space / mates ; reduction in prey ; poaching / hunting / poisoning (by humans) disease

Question 52

With reference to the three types of vectors that are commonly used, discuss the challenges in choosing appropriate vectors for use in gene therapy. | (9700/42/m/j/20)

Answer 52

naked DNA 1 has to be injected into target cell / lack of organ-specific delivery ; 2 low efficiency of cellular uptake ; 3 rapidly broken down ; viruses 4 small packaging capacity / only small amount of DNA can be carried ; 5 low probability of integration (into host genome) ; 6 cause mutations in host DNA / (gene) insertion disrupts gene function / insertional mutagenesis ; liposomes 7 low ability to, add DN A / genes, into target cells (genome) / low transduction efficiency ;

Question 53

outline how genetic engineering gave the trait of insect resistance | (9700/41/m/j/19)

Answer 53

1 gene(s) from, another species / (soil) bacterium / B.(acillus) thuringiensis ; 2 restriction, enzyme / endonuclease ; 3 (Ti) plasmid / Agrobacterium (tumefaciens) / vector / virus / liposome / gene gun ; 4 (DNA) ligase ; 5 (forms) recombinant, DNA / plasmid / vector ; 6 new gene / rDNA / plasmid, enters, maize / MON810, embryos / cells / genome / DNA ; 7 gene, expressed / transcribed (and translated), to make, protein / toxin ; 8 ref. to marker genes / insert promoter

Question 54

state why they decided to calculate standard error | 9700/51/m/j/20

Answer 54

To find the closessness to the true mean to graph error bars

Question 55

explain why they used t-test to analyse the data | 9700/51/m/j/20

Answer 55

data is continous and normally distributed comparingg the 2 sets of mean

Question 56

Triploid watermelon plants develop edible fruits but these are sterile and do not contain seeds, making them more enjoyable to eat. Explain why the fruits of the triploid plants are sterile and do not contain seeds. | 9700/43/m/j/20

Question 57

Suggest how a tumour in the hypothalamus can lead to a person producing a large volume of dilute urine. | 9700/43/m/j/20

Answer 57

ref. (effect on) neurosecretory cells in hypothalamus ; production / synthesis, of ADH, decreases / stops ; idea of less ADH secreted (into blood) by posterior pituitary ; collecting duct walls less permeable to water ; water remains in collecting duct / most water remains in urine ;

Question 58

Suggest how an increase in adrenaline results in an increase in blood temperature. | (9700/43/m/j/20)

Answer 58

1 increased, glycogenolysis / glucose available ; 2 (so) increased respiration ; 3 (so) more heat energy generated (and transferred to blood) ;

Question 59

describe how you would carry out a belt transect to assess the ditribution and abundance of organisms in an area | (9700/43/m/j/20)

Answer 59

1 lay out a, line / tape ; 2 (line / tape) runs from low tide area to high tide area ; 3 ref. to use of quadrats ; 4 ref. to interrupted belt transect ; 5 place quadrats at regular intervals ; 6 measure species frequency ; 7 use of key or Braun Blanquet / other named, scale ; 8 repeat sampling ;

Question 60

explain the relationship between the gene mutation thaat caused sickle cell anamia and the reduced oxygen carrying capacity of red blood cells | 9700/42/f/m/22 3a

Answer 60

(sickle cell anaemia is) homozygous recessive ; HBB (allele / gene) ; base / nucleotide, substitution change in, triplet / codon GAG to GTG / A to T ; causes, change in amino acid (sequence) / glutamic acid to valine ; valine is non-polar ; causes change in, 3D shape / tertiary structure / quaternary structure / globular structure (of haemoglobin) ; haemoglobin has lower affinity for oxygen ; (in red blood cells) haemoglobin, less soluble / sticks together / forms fibres ; (red blood) cells become sickle shaped ;

Question 61

outline the role of sarcoplasmic reticulum in the contraction oof straighted muscle | 9700/41/o/n/20 6c)

Answer 61

Ca2+ channels open ; Ca2+, diffuses / released, into sarcoplasm ; Ca2+ binds to troponin ; tropomyosin, moves / changes position ; cross-bridges form / myosin binds to actin ;

Question 62

Explain 2 ways in which the mammalian body uses this extra oxygen | 9700/41/o/n/20 7b

Answer 62

lactate, converted / oxidised ; to, pyruvate / glucose / glycogen ; haemoglobin / myoglobin, re-oxygenated

Question 63

outline reasons why it is important to maintain biodiversity

Answer 63

1 aesthetic / leisure, reasons ; 2 moral / ethical, reasons ; 3 resource material ; 4 economic benefits for local community / (eco)tourism ; 5 maintain / do not disrupt, food webs / food chains / ecosystem ; 6 mineral (re)cycling ; 7 maintain, large gene pool / genetic variation ;

Question 64

describe and explain the properties of plasmids that allow them to be used in gene cloning | 9700/41/o/n/20 9a)

Answer 64

1 double stranded DNA ; 2 have, restriction site / target sequence for restriction enzyme ; 3 allows gene (for cloning) to be inserted ; 4 small ; 5 plasmid can, enter / transform, (host) cell / bacterium ; 6 circular ; 7 stable ; 8 contain, (named) marker genes / (named) genes for antibiotic resistance ; 9 used to identify, GM / transformed / recombinant, (bacterial) cells ; 10 replicate, fast / independently (of host cell replication) ; 11 get many copies of cloned gene ;

Question 65

Explain the roles of restriction endonucleases, ligases and reverse transcriptase in genetic engineering | 9700/41/o/n/20 9b)

Answer 65

restriction endonucleases 1 cut DNA ; 2 at, restriction site / specific (base) sequence / target sequence ; 3 ref. to palindrome ; 4 give, sticky / blunt, ends ; ligases 5 join gene to, plasmid / (named) vector ; 6 seal (sugar-phosphate) backbone ; 7 make, phospho(di)ester / covalent, bonds ; 8 make recombinant, DNA / plasmid / vector ; reverse transcriptase 9 makes cDNA ; 10 from mRNA ; 11 ref. to DNA single-stranded initially ;

Question 66

explain how random assortment of homologous chromosomes also results in genetic variation | 9700/42/f/m/21

Answer 66

homologous chromosomes / bivalents, align independently of each other ; at the, equator / metaphase plate ; idea that this leads to different combinations of chromosomes in the daughter cells ; results in new combinations of alleles ;

Question 67

WHy is phenotypic ratios of F2 generation do not always match the expected ratios | 9700/42/f/m/22

Answer 67

does not consider possiblity of 1 epistasis ; 2 linkage ; 3 lethal allele ; 4 chance deviations ; 5 environmental effects ; 6 mutations ; 7 small sample size ;

Question 68

Adaptations of chloroplast according to its functions | 9700/M/J/41/22

Answer 68

thylakoid(s) / granum / grana light dependent reaction / photophosphorylation ; 2 thylakoid membrane(s) have (named), pigments / photosystems / LHC / electron carriers / ETC / ATP synthase ; 3 thylakoid membranes / grana, have large surface area / are many in number to absorb (more) light ; 4 stroma for light independent reaction / Calvin cycle ; 5 stroma has, (named) enzymes / RuBP / reduced NADP ; 6 stroma colourless OR stroma contains water so light reaches thylakoids OR as a medium for reactions / for photolysis 7 DNA / ribosomes make (named), chloroplast proteins / proteins for photosynthesis ; 8 starch grains / lipid droplets store, (named) product of photosynthesis / (chemical) energy ;

Question 69

diffrences between chemiosmosis in mitrochondria and chloroplast | 9700/M/J/41/22

Answer 69

mitochondrion: oxidative phosphorylation in the cristae H+ transported to the intermebrane NADR gives the e- oxygen is the final acceptor Chloroplast: Photophosphorylation H+ into the tylakoid lumen from the thylakoid membrane photolysis of water gives the e- NAD is the final acceptor

Question 70

social benifits of gene editing in crops | 9700/M/J/41/22

Answer 70

1 more food / increase yield / help solve global demand for food ; 2 improves quality of, fruit / oranges / crop ; 3 more income for, growers / farmers ; 4 cheaper / lower cost, fruit / oranges / food (to consumer) ; 5 spend less on / use less / no need for, (bactericidal) chemicals / pesticides ;

Question 71

Explain why improving milk yields in cattle by selective breeding can be more challenging than improving yields of crops by selective breeding. | 9700/42/F/M/22

Answer 71

1 longer time to, grow / mature ; 2 fewer offspring (per cross / AW) ; 3 feature can only be measured in, about 50% of offspring / females ; 4 milk yield must be measured over period of time ; 5 ref. to ethical issues ; 6 ref. to difficulty in identifying suitable males for use in crosses ; 7 cattle require more, care / support or more expensive ; 8 e.g. more dangerous to carry out breeding of large cattle

Question 72

explain why herbicides that prevent cyclic photophosphorylation and non cyclic photophosohorylation stop carbohydrate being produced in the chloroplast | 9700/43/M/J/22

Answer 72

No regeneration of RUBP no GP or TP no ATP and NADR

Question 73

state two features of a spinal reflex other than being fast | 9700/42/o/n/20

Answer 73

involuntary stereotipic

Question 74

describe a method that could be used to estimate the population size of a mobile animal such as brown rat | 9700/42/o/n/20

Answer 74

mark–release–recapture ; 2 capture (sample of) rats and count them ; 3 ref. to humane traps ; 4 mark so as to not adversely affect rats or describe method of marking such as, tagging / using dyes ; 5 return to where they were caught / AW ; 6 allow time to mix (with population) / AW ; 7 capture second sample ; 8 count number caught and number marked ; 9 population size estimate (M1) = AVP ; e.g. repeat

Question 75

describe the role of abscisic acid in stomal closure | 9700/42/F/M/22

Answer 75

bunds to receptors on cell surface membrane proton pump is inhabited protons are not pumped out k+rushes out of the cell by facilitated diffusion water also moves out by osmosis making the gaurd cell flaccid and stoma shrinks

Question 76

compare the characteristics of memebers of the domain Archaea and Bacteria | 9700/42/F/M/22

Answer 76

Similarities : both are prokaryotes (No nucleus or mbo) Both have circular DNA Both has 70s ribosomes reproduce by binary fission Diffrences : Bacteria have a cell wall made of peptidoglycon Archaea dont Bacteria has ester links lipids and Archaea has ether linked lipids Bacteria forms spores and Archaea dont

Question 77

state additional informaation about the data that can ained from the calculated values of 95% CI | 9700/52/f/m/21

Answer 77

95% probability the actual mean is close within limits the diffrence b/w mean is significantt for trampled and untrampled The narrower the untrampled CI the closer the calculated mean to the true mean

Question 78

explain the relationship b/w absorption spectrum and action spetrum for photosynthesis | 9700/41/o/n/22 2b

Answer 78

action spectrum shows rate of photosynthesis for light (wavelenghts) absorption spectrum shows how much each wavelegth is absorbed Higher absoption gives higher photosynthesis Directly proportional

Question 79

Outline how the light independant stage of photosynthesis leads to the production of carbohydrate such as starch in plant leaves | 9700/41/o/n/22 2d

Answer 79

RUBP joins CO2 forming GP (6c) GP turns into TP loosing carbon and hydrogen to ATP and NADR Tp can be stored as glucose and anyother cybohydrates that forms starch

Question 80

how are cells in the pct adapted to their function | 9700/42/o/n/22

Answer 80

1 microvilli for large surface area (for reabsorption) ; 2 (large surface area) for many, cotransporters / carrier proteins ; 3 cotransporter (proteins) to absorb sodium ions with, glucose / amino acids ; A idea of secondary active transport 4 tight junctions between cells so substances have to pass through the cells / AW ; 5 many mitochondria to produce ATP ; 6 (ATP) for the sodium (potassium) pumps or (ATP) to pump / actively transport, sodium ions (into the blood) ; 7 folded basal membrane for many sodium (potassium) pumps ;

Question 81

describe 2 processes in the liver that are stimulated by glucagon | 9700/42/m/j/21

Answer 81

glycogenolysis: breaking down glycogen to form glucose glucagonesis: synthesis of glucose from non carbohydrate sources like amino acid, glycerol and lactic acid

Question 82

what is meant by negative feed back | 9700/42/m/j/21

Answer 82

1 change in a parameter ; 2 detected by receptor ; 3 coordination / described ; 4 (corrective) action taken by effector ; 5 return to, set point / norm / optimum ;

Question 83

outline examples of movement in cells that use ATP | 9700/42/m/j/21

Answer 83

Exocytosis, endocytosis, phagocytosis protein synthesis DNA replication, mitosis, meisis, spindlr fibre movement flagella active transport

Question 84

explain why the phenotype do not show the predicted ratio | 9700/42/m/j/21/7bii

Answer 84

1 (two) genes are linked / autosomal linkage or alleles inherited together ; 2 no, independent / random, assortment ; 3 large numbers of parental type offspring / small numbers of recombinant offspring ; 4 recombinants due to crossing over ; 5 during, meiosis / prophase 1 / gamete formation ;

Question 85

describe the genetic basis for continuous variation | 9700/42/m/j/21

Answer 85

1 different alleles at a single gene locus have small effects (on the phenotype) ; 2 different genes may have an, additive / combined, effect (on the phenotype) ; 3 polygenic traits that can be influenced by 2 or more genes for characteristics such as heights/ skin color

Question 86

suggest 2 enviromental factors that may effect the body mass of an animal | 9700/42/m/j/21

Answer 86

avalability of food quality of food disease tempreture

Question 87

outline the principle of selective breeding | 9700/42/m/j/21

Answer 87

1 take parents of desired characteristics and breed them together 2 when sucessfukky bred, breed the offspring together with desired characterestics 3 repeat for more generations this may lead to innbreeding depression so it is advised to be avoided

Question 88

adaptations of mitrochondria | 9700/42/m/j/21

Answer 88

1 (function is) to make ATP ; 2 ref. to double membrane / outer and inner membrane / envelope ; inner membrane 3 folded / cristae, to increase / for large, surface area ; 4 has, ATP synthase / stalked particles ; 5 has, ETC / carrier (proteins) / cytochromes ; 6 (site of) oxidative phosphorylation / chemiosmosis ; 7 impermeable to protons ; intermembrane space 8 has low pH / high concentration of protons ; 9 protons pumped into intermembrane space ; 10 proton gradient between intermembrane space and matrix or protons diffuse from intermembrane space to matrix; matrix 11 contains (co)enzymes for, link reaction / the Krebs cycle ; outer membrane 12 permeable to, pyruvate / reduced NAD / oxygen ; 13 AVP ; e.g. ribosomes / DNA, involved in protein synthesis

Question 89

compare gene editing and selective breeding | 9700/42/f/m/24/4d

Answer 89

similarities: first offspring with the allele can have unknown effects presence of allele can be confirmed ib offspring by genetic done by humans/ artificial methods Diffrences: gene editing where 1 gene is affected and all springs have the same allele in 1 generation performed on embryos and zygotes Genetic technology has technical requirements selective breeding has physiological requirments gene editing maintains desired characteristics selective breeding does not outbreeding not required for genetic variation in gene editing but required in selective breeding

Question 90

suggent why the green flourescent protien if sometimes transferred in addition to the desired gene in genetic engineering | 9700/41/m/j/24

Answer 90

acts as a marker gene to identify the recombinant organism