Question 1:
(a) Glycolysis is a biochemical pathway that occurs in the cytoplasm of cells.
In glycolysis, a molecule of glucose is metabolised to two molecules of pyruvate. The process is outlined in Fig. 1.1.
(i) Explain why glucose is phosphorylated at the beginning of glycolysis.
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(ii) Suggest one use of the reduced NAD that is produced in glycolysis.
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(iii) Name the type of phosphorylation reaction by which ATP is made during glycolysis.
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(b) Pyruvate can enter the mitochondrion by active transport.
Describe the main conditions that are required for pyruvate to enter the mitochondrion by active transport.
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(c) Pyruvate is involved in the link reaction in the matrix of the mitochondrion.
Describe the link reaction.
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▶️Answer/Explanation
Ans: 1(a)(i) any one from:
glucose
is activated / made reactive ;
becomes unstable ;
cannot leave cell ;
energy level increased ;
concentration gradient maintained ;
1(a)(ii) any one from:
carrier / acceptor / provider, of, hydrogen (atoms) / electrons
or
provider of H ions and electrons ; R H ions alone
used for redox reactions ;
used to reduce, ethanal / pyruvate ;
1(a)(iii) substrate-linked / substrate level ;
1(b) any three from:
1 (inner) mitochondrial membrane impermeable (to pyruvate) ;
2 carrier (protein) ; A symport / MPC (mitochondrial pyruvate carrier)
3 lower concentration of pyruvate outside mitochondrion ora
or
against concentration gradient ;
4 oxygen available ;
5 ATP / energy ;
1(c) any three from:
1 decarboxylation ; A description
2 dehydrogenation / oxidation, (of pyruvate) ; A description
3 reduced NAD produced ;
4 formation of, acetyl coenzyme A / acetyl CoA ;
Question 2:
(a) In sexual reproduction, meiosis occurs to produce haploid gametes from a diploid cell.
Explain the meaning of the terms haploid and diploid.
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(b) Describe the behaviour of chromosomes during the main stages of meiosis I in animal cells.
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metaphase I ………………………………………………………………………………………………………………
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anaphase I ………………………………………………………………………………………………………………..
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telophase I ………………………………………………………………………………………………………………..
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(c) The production of haploid gametes by meiosis also involves division of the cytoplasm.
State the term used to describe this division of the cytoplasm.
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▶️Answer/Explanation
Ans: 2(a) haploid is one (complete) set of chromosomes ;
diploid is two (complete) sets of chromosomes ;
if only comparative statement = max 1
e.g. haploid is n chromosomes and diploid is 2n
haploid is half the number of chromosomes as diploid / AW
2(b) prophase I
chromosomes / chromatin, condense / shorten / fatten I DNA
or
homologous chromosomes pair up / bivalents form
or
crossing over / synapsis / chiasmata formation ;
metaphase I
homologous (pairs of) chromosomes / bivalents, line up on the, equator / metaphase plate
or
random / independent, assortment, of homologous (pairs of) chromosomes / bivalents ;
anaphase I
chromosome(s) / one of each pair of chromosomes, moves (to pole / end of cell) ;
telophase I
chromosomes reach the opposite, poles / centrosomes / centrioles / end of cell
or
chromosomes decondense / chromatin formation / chromosomes become diffuse ;
2(c) cytokinesis ;
Question 3:
(a) The sea blush, Plectritis congesta, is a flowering plant that grows on the west coast of North America.
Individual sea blush plants produce fruit that is either winged or wingless. Investigations have
shown that this characteristic is controlled by a single gene with two alleles:
• a dominant winged fruit allele
• a recessive wingless fruit allele.
Fig. 3.1 shows the difference in structure between winged fruit and wingless fruit phenotypes.
(i) A large sample of sea blush fruits was collected and their fruit-wing characteristic was recorded.
Name the type of variation that is shown for the fruit-wing characteristic of the sea blush.
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(ii) Different sea blush plants can have fruit with different colours.
Suggest two ways in which a new fruit colour could naturally occur in a sea blush population.
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(iii) 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.
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(b) Natural selection occurs in populations, such as in populations of sea blush plants.
Explain why natural selection occurs in populations.
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▶️Answer/Explanation
Ans: 3(a)(i) discontinuous ;
3(a)(ii) any two from:
1 mutation A description
or
(formation of a) new allele ;
2 change in, environment / selection pressure ; A description
3 cross pollination / cross breeding / hybridisation ;
4 new allele combination / codominant alleles together ;
3(a)(iii) any three from:
both types
1 (inter)breed to produce fertile offspring / not reproductively isolated ;
2 occupy the same niche ;
3 same / similar, morphology / physiology / biochemistry ;
A description I fruit shape
4 have, similar / same, genes / DNA sequences / genomes ;
5 similar / same, proteins / amino acid sequences ;
3(b) any five from:
1 (populations) can produce many offspring / AW ;
2 genetic variation occurs (in populations) / described ;
3 ref. mutations / sexual reproduction / gamete formation / random fertilisation ;
4 ref. competition qualified ; e.g. mates / food / resources
5 ref. selection pressure ;
6 some individuals have advantageous, adaptations / phenotype / traits / AW ;
7 (so) they, survive / reproduce / have a selective advantage ;
8 (so) pass on their advantageous allele(s) ;
9 (so) the (advantageous) allele frequency increases ;
Question 4:
Genetic technology uses many different enzymes and techniques.
(a) Restriction endonucleases are used in genetic modification. These enzymes occur naturally
in prokaryotic cells. More than 3500 different restriction endonucleases have been identified
and it is thought there are many more to discover.
Name two domains that are a source of restriction endonucleases.
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(b) Originally, the method used to obtain a restriction endonuclease was to:
• grow large numbers of the specific prokaryotic cells that are the source of the enzyme
• break open the cells and extract and purify the restriction endonuclease.
This original method produced only a small quantity of restriction endonuclease and was not economical.
The newer method for large-scale production is to:
• obtain the gene coding for a specific restriction endonuclease
• introduce the gene into Escherichia coli, with a promoter that allows the gene to be expressed continuously.
The newer method increases the quantity of specific restriction endonuclease produced.
Suggest and explain the steps needed to carry out the newer method for large-scale
production of a specific restriction endonuclease.
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(c) Describe the advantages of databases for the study and use of restriction endonucleases.
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(d) Electrophoresis is a technique used in genetic technology.
Paper chromatography is a technique used to investigate the photosynthetic pigments found in chloroplasts.
Compare the similarities and differences between electrophoresis and chromatography.
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▶️Answer/Explanation
Ans: 4(a) Bacteria and Archaea ;
4(b) any four from:
1 obtain (specific restriction endonuclease) gene, qualified ;
e.g. gene extracted from the, DNA / genome, of E. coli / bacteria
gene synthesised from the mRNA of E. coli / bacteria
gene synthesised from nucleotides
2 PCR to make more copies of, gene / DNA ;
3 cut a plasmid, with a restriction enzyme / to give sticky ends ;
4 combine / mix / join, gene with plasmid using ligase ;
5 add plasmid to, E. coli / bacteria ; A transformation of E. coli
6 use marker genes to, select / identify, bacteria / E. coli, with recombinant plasmids ;
7 ref. culture bacteria / use fermenter ;
8 ref. extraction / purification (of enzyme) ;
9 AVP ; e.g. heat shock / calcium ions / electroporation (detail mp5)
complementary sticky ends anneal / make phosphodiester bonds (detail mp4)
4(c) any three from:
1 (data stored is) a large amount of, amino acid / nucleotide / base / DNA, sequences ;
2 share data / access data quickly ;
3 compare (amino acid / nucleotide / base / DNA) sequences ;
4 use to, predict / visualise / model, the structure of the enzyme ;
5 identify restriction endonuclease to use
or
find / discover, new restriction endonucleases ;
4(d) any four from:
Question 5:
(a) Warfarin is a poison used to kill rats. Some rats are resistant to warfarin and can survive the
effects of the poison. Warfarin resistance is due to a mutant dominant allele at a single gene locus.
Researchers investigated the population of brown rats on a large island where there are no
predators of rats. On this island, warfarin is used to try to control the rat population.
The researchers found that 40% of the population of rats was resistant to warfarin.
(i) Use Hardy–Weinberg equation 1 and equation 2 to calculate the percentage of the
population of rats on the island that is heterozygous for warfarin resistance.
equation 1 p + q = 1
equation 2 p$^{2}$ + 2pq + q$^{2}$ = 1
Show your working.
answer …………………………………………….. %
(ii) In natural populations, it is usual to find that only some of the conditions of the Hardy–Weinberg principle are met.
Suggest and explain which of the conditions of the Hardy–Weinberg principle are most likely to be met for the island population of brown rats.
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(b) Dominant advantageous alleles and recessive advantageous alleles both naturally occur in populations.
Explain why, when a new dominant advantageous allele occurs, its frequency increases
more quickly in the population than when a new recessive advantageous allele occurs.
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▶️Answer/Explanation
Ans: 5(a)(i) q$^{2}$ = 0.6
or
q = √ 0.6
or
q = 0.775
or
p = 0.225 ;
2pq = 2 0.225 × 0.775 or 0.35 ; allow ecf from mp1
35 % ; allow ecf from mp2
5(a)(ii) any four from:
1 no migration
or
no flow of, alleles / genes, into / out of, the population ;
2 population is isolated / described ; e.g. separated by geographical barrier
I ref to island alone
3 random mating is occurring ;
4 rats move around island / AW ;
5 large population ;
6 rats have high reproductive rate / no predators ;
7 rats are diploid ;
8 have two different alleles (for the gene) / heterozygous ;
5(b) any three from:
1 new allele initially found in heterozygotes ;
dominant advantageous allele
2 (new) dominant allele is, expressed in heterozygote / always expressed ;
3 selection can act on individuals with dominant allele straight away / AW ;
recessive advantageous allele
4 (new) recessive allele is not expressed, in heterozygote / due to dominant allele
or
recessive allele only expressed in homozygous recessive (genotype) ;
5 selection can only act on individuals who are homozygous recessive ;
6 it takes time for homozygous recessive (genotype) to occur / AW ;
Question 6:
(a) Fig. 6.1 is a photomicrograph of a section through a Bowman’s capsule and a glomerulus.
On Fig. 6.1, use label lines and letters to label:
F – the location of the glomerular filtrate
P – the location of the blood plasma.
(b) The glomerular filtration rate (GFR) is the rate at which fluid filters from the blood in the glomerulus into the Bowman’s capsule.
Fig. 6.2 shows the mean GFR values for healthy males and females of different age groups.
(i) Use Fig. 6.2 to calculate the yearly rate of decrease in mean GFR from the 20–29 age group to the 80–89 age group for females.
Show your working.
Give your answer to one decimal place and include units.
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(ii) The age of a person and whether they are male or female can affect GFR.
Suggest and explain other factors that can affect GFR.
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(c) The glomerular filtrate passes from the Bowman’s capsule to the proximal convoluted tubule,
where selective reabsorption takes place.
Describe the process of selective reabsorption.
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▶️Answer/Explanation
Ans: 6(a)
6(b)(i) $ \frac{118-52}{60} or \frac{118-52}{69} or \frac{118-52}{51}$
1.1 or 1.0 or 1.3 ;
cm$^{3}$ min$^{-1}$ y$^{-1}$ ; A cm$^{3}$ min$^{-1}$ / year
A year(s) $^{-1}$
R yr or yrs or mins
6(b)(ii) any three from:
1 high(er), hydrostatic / blood, pressure causes higher GFR ; ora
2 water / solute, potential gradient between glomerulus and Bowman’s capsule affects GFR ;
3 kidney disease / named, decreases GFR ;
e.g. damage to nephron or basement membrane / cancer
4 dehydration / lower water potential of blood, decreases GFR ; ora
5 high altitude decreases GFR ; ora
6 drugs / named, affects GFR ;
e.g. diuretics / beta blockers / vasodilators / NSAIDS / ACE inhibitors
7 larger difference between afferent arteriole lumen and efferent causes higher GFR ; ora
6(c) any seven from:
1 Na$^{+}$, actively transported / pumped, out of cells ;
2 Na$^{+}$ enter blood ;
3 Na$^{+}$ concentration in cells decreases
or
Na$^{+}$ concentration gradient (between pct lumen and cytoplasm) / described ;
4 Na$^{+}$ enter cells from, filtrate / lumen ;
5 by facilitated diffusion ;
6 cotransport of, glucose / amino acids ; I secondary active transport
7 water potential of cells decreases ;
8 water enters cells from (filtrate / lumen) by, osmosis / down the water potential gradient ;
9 glucose / amino acids, leave cells by, (facilitated) diffusion / described ;
10 glucose / amino acids, reabsorbed or move into , tissue fluid / blood ;
11 AVP ; e.g. other named ions reabsorbed
Question 7:
(a) A striated muscle cell (muscle fibre) will contract when stimulated by a motor neurone at a neuromuscular junction.
Air temperature can affect the temperature of striated muscle cells.
Investigations have shown that the efficiency of contraction of striated muscle cells decreases when the air temperature decreases.
Suggest reasons why a reduction in temperature can decrease the efficiency of contraction of striated muscle cells.
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(b) The greater blue-ringed octopus, Hapalochlaena lunulata, produces tetrodotoxin (TTX). TTX
is a neurotoxin. If a mammal is bitten by this octopus, the effect of TTX can cause the death of the mammal.
Fig. 7.1 shows a greater blue-ringed octopus.
TTX binds to voltage-gated sodium ion channels in the axon of a neurone and changes the tertiary structure of the channel protein.
Suggest how TTX may affect the functioning of a motor neurone.
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▶️Answer/Explanation
Ans: 7(a) any four from:
1 respiration rate decreases / less ATP produced ;
2 reduces activity of (named) enzymes / description ;
3 reduces movement of, Ca$^{2+}$ / Na$^{+}$ / ACh / neurotransmitter ;
4 (in neuromuscular junction)
less / no, acetylcholine broken down
acetylcholine remains attached to receptors
acetylcholinesterase, less active / inactive ;
5 (in sarcomere)
fewer / no, Ca$^{2+}$ bind to troponin
fewer / no, cross bridges formed
fewer / no, power stokes ;
6 (in sarcomere)
less / no, detachment of myosin heads (from actin)
fewer / no, cross bridges broken
ATPase / myosin head, less active / inactive
hydrolysis of ATP, slower / stops ;
7 AVP ; e.g. shivering / reduced blood flow to muscle / energy diverted for thermoregulation (idea)
7(b) any three from:
1 Na$^{+}$ channels don’t open A Na+ do not, diffuse / move, into neurone
or
stay open ; A Na$^{+}$ always, diffuse / move, into neurone
2 (axon) membrane, cannot be depolarised
or
(axon) membrane stays depolarised ;
3 no action potentials, generated / transmitted (along motor neurone)
or
continuous action potentials, generated / transmitted (along motor neurone) ;
4 Ca$^{2+}$ does not enter presynaptic knob / vesicles not stimulated to move / no ACh release (at neuromuscular junction)
or
Ca$^{2+}$ always enters presynaptic knob / vesicles always stimulated to move / ACh continually released (at neuromuscular junction) ;
5 consequence e.g. paralysis / described
or
continued muscle contraction ;
Question 8:
(a) In plants such as rice, Oryza sativa, rubisco has a low rate of activity, which in turn affects the
rate of photosynthesis. The cereal crop sorghum, Sorghum bicolor, has a high rate of activity of rubisco.
A genetically modified (GM) variety of rice was produced. Parts of the quaternary structure of
rubisco in rice were altered to be the same as the rubisco in sorghum.
The rate of activity of rubisco in non-GM rice and GM rice was measured at different
concentrations of atmospheric carbon dioxide (CO$_{2}$).
The results are shown in Fig. 8.1.
(i) Compare the two curves shown in Fig. 8.1 and explain why the curve for non-GM rice levels off.
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(ii) Suggest which part of the rubisco molecule was altered to produce the GM variety of rice.
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(b) Fig. 8.2 shows an outline of the Calvin cycle.
(i) Name the process that involves the enzyme rubisco.
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(ii) State the type of reaction that occurs when GP is converted to TP.
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(iii) RuBP is regenerated from molecules of TP.
State how many molecules of RuBP are produced from 10 molecules of TP.
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(iv) TP molecules that are not involved in the regeneration of RuBP can be used in the synthesis of other molecules.
State two molecules that can be produced from these TP molecules.
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▶️Answer/Explanation$_{2}$
Ans: 8(a)(i) any two from:
1 higher rate of activity (of rubisco) in GM rice (throughout) ;
2 (low CO$_{2}$ concentrations) rate of activity for both increases ;
3 comparative figures – GM and non-GM at one CO$_{2}$ concentration ;
8(a)(i) plus
levels off because:
4 carbon dioxide concentration no longer limiting
or
light intensity limiting
or
temperature limiting
or
rubisco active sites saturated (with carbon dioxide)
or
less RuBP available ;
8(a)(ii) active site ; A allosteric site
8(b)(i) carbon (dioxide) fixation ; A carboxylation
8(b)(ii) reduction / hydrogenation ;
8(b)(iii) 6 / 5 ;
8(b)(iv) any two from: list rule
1 hexose / named ; e.g. glucose / fructose
2 disaccharide / named ; e.g. sucrose / maltose
3 starch / cellulose ;
4 amino acids ;
5 glycerol / fatty acids ;
Question 9:
(a) The passage outlines the endocrine system.
Complete the passage by using the most appropriate scientific terms.
The endocrine system consists of tissues and ……………………………………………………….. ,
which secrete hormones such as insulin, glucagon and antidiuretic hormone (ADH).
Glucagon only affects target cells that have complementary receptors, which are located
on the ……………………………………………………….. . Glucagon binds to these receptors
and this leads to the production of a ……………………………………………………….. , which
transfers the signal throughout the cytoplasm. The target cells for insulin are in the liver,
……………………………………………………….. and adipose tissue. The target cells for ADH are
those of the distal convoluted tubule and the ……………………………………………………….. of the
kidney nephron. These hormones are involved in ……………………………………………………….. ,
which is the maintenance of a constant internal environment.
(b) The blood glucose concentration of a person was measured at regular intervals after the ingestion of a meal rich in glucose.
Fig. 9.1 shows the results of this investigation.
(i) Explain how the blood glucose concentration is reduced during phase A of the curve.
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(ii) Suggest why the blood glucose concentration increases again during phase B.
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▶️Answer/Explanation
Ans: 9(a) glands ;
cell surface membrane / plasma membrane ; A liver (cells)
second messenger / cAMP ; A enzyme cascade / phosphorylation of enzymes / signalling cascade
(striated) muscles ;
collecting duct ;
homeostasis ;
9(b)(i) 1 insulin, produced / released ;
2 increase in uptake of glucose into cells ;
3 detail of uptake ; e.g. increase permeability of cell surface membrane (to glucose) / GLUT added to cell surface
membrane
4 increase / stimulates, respiration of glucose (in cells) / phosphorylation of glucose ;
5 (stimulates) glycogenesis / conversion of glucose to lipids ;
9(b)(ii) ref. glucagon ;
Question 10:
(a) Many zoos around the world are involved in captive breeding programmes for endangered species.
Outline the role of zoos in the conservation of endangered species, other than captive breeding programmes.
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(b) Chester Zoo, in the United Kingdom, controls the European captive breeding programme for the eastern black rhinoceros, Diceros bicornis michaeli.
Fig. 10.1 shows an eastern black rhinoceros.
In the captive breeding programme for the eastern black rhinoceros, 15.8% of females breed each year while in the wild 23.7% of females breed each year.
Suggest reasons why fewer females breed in captivity than in the wild.
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(c) Sometimes assisted reproduction is used in captive breeding programmes for the eastern black rhinoceros.
Fig. 10.2 outlines the process of IVF that is used in these programmes.
Outline:
• the event A that occurs in the production of the embryos
• the two other possible outcomes, B and C, for the embryos that have been produced.
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▶️Answer/Explanation
Ans: 10(a) any three from:
1 safe location
or
protected from, predators / hunters / poachers ;
2 research qualified ; e.g. disease control / into diet / behaviour
3 raise funds ;
4 work with local, communities / governments or conservation projects ;
5 education / raise awareness ;
6 medical / veterinary / health, (care) ;
10(b) any four from:
1 unnatural environment / described ; ora
2 effect of captivity on fertility ;
3 refuses to mate ;
4 low availability of suitable mates / AW ; ora
5 stress / pressure ;
6 AVP ; e.g. zoo capacity / zoos control number they breed
10(c) A – fertilisation occurs / sperm or semen added ;
B and C – surrogacy / described ;
cryopreservation / described ;