Energy and respiration

8(a)(i) A – label line pointing to mitochondrial matrix ; 1 8(a)(ii) crista(e) ; 1 8(a)(iii) any five from: 5 1 folded (inner) membrane / many cristae ; 2 forms large surface area ; 3 (for) electron carriers / electron transport chain / ETC / cytochromes ; 4 ref. to ATP synth(et)ase / ATP synthesis ; 5 impermeable to, protons / hydrogen ions ; 6 (so) allows, formation of proton gradient / high concentration of protons in intermembrane space ; 7 proton pumps ; © UCLES 2021 Page 17 of 22 8(b) DCPIP / methylene blue ; 2 changes, colour / blue to colourless, when, reduced / accepts electrons (from succinate) ; 8(c)(i) any three from: 3 1 rate of respiration increases (as succinate concentration increases) up to 1.0 mmol dm–3 or maximum rate at 1.0 mmol dm–3 ; 2 rate of respiration higher at 37 °C than at 10 °C (in liver and muscle) ; 3 rate of respiration higher in muscle than in liver (at both temperatures) ; 4 comparative data quote to support mp2 or mp3 ; 8(c)(ii) any three from: 3 muscles have higher rate of respiration because: 1 respiration produces ATP ; 2 muscle has higher need for, ATP / energy ; ora 3 for muscle contraction or muscle is more metabolically active / AW ; 4 AVP ; e.g. shivering to maintain body temperature ; 8(c)(iii) muscle, is contracted / generates heat / is more metabolically active / AW ; ora 1 © UCLES 2021 Page 18 of 22

2(a)(i) any two from: 2 idea of synthesis from smaller units 1 DNA replication / transcription ; 2 to, make / build up, (named) protein ; 3 to, make / build up, (named), lipid / triglyceride / phospholipid ; 4 to, make / build up, (named) carbohydrate / polysaccharide ; 5 phosphorylation ; 2(a)(ii) any three from: 3 1 phosphorylates glucose or glucose  glucose / fructose / hexose, phosphate ; 2 second phosphorylation or glucose / fructose / hexose, phosphate  fructose / hexose, bi(s)phosphate ; 3 so glucose cannot leave the cell ; 4 activates / increases energy of / decreases stability of, glucose ; 2(b)(i) any three from: 3 decreased production of ATP 1 smaller / less steep, proton gradient ; 2 few(er) protons go through, ATP synth(et)ase / stalked particle ; increased lipid metabolism 3 use / burn / respire, body fat / lipid stores ; 4 as less ATP made from, glucose / food ; 2(b)(ii) any two from: 2 1 more / faster / increased, (rate of) glycolysis ; 2 oxygen, decreased / used faster / shortage ; 3 (so) more / increased, anaerobic respiration ; 2(b)(iii) any one from: 1 energy from, reduced NAD / ETC, released as heat ; energy not used to join ADP and Pi so released as heat ; © UCLES 2021 Page 7 of 16

9(a) any eight from: 8 1 vary / different / range of, glucose / fructose, concentrations ; 2 control / same, volume of yeast (suspension) ; 3 control / same, volume of glucose (solution) ; 4 control / same, volume / concentration, of indicator (solution) ; 5 control temperature (between 20–45oC) ; 6 oil layer to exclude, air / oxygen ; 7 indicator turns from blue (start / oxidised) to colourless (end / reduced) ; 8 due to, hydrogen atoms / H+ / electrons, from, glycolysis / dehydrogenation / respiration ; 9 time how long it takes for colour change OR fix time interval and measure with colorimeter ; 10 repeat experiment ; 11 calculate mean(s) ; 12 graph with glucose concentration (on x axis) and, time taken / % absorbance / % transmission / rate (on y) ; 13 rate is 1/t ; 14 AVP ; © UCLES 2021 Page 14 of 16 9(b) any seven from: 7 both 1 occur in cytoplasm ; 2 (only) involve glycolysis ; 3 make, 2 (net) / small amount of, ATP ; 4 regenerate NAD (from NADH) ; comparison mammalian tissue yeast cells 5 H acceptor / reduction of pyruvate / pyruvic acid ethanal 6 (end) product lactate / lactic acid ethanol 7 no, CO decarboxylation CO 2 / 2 8 (enzyme) lactate dehydrogenase ethanol dehydrogenase 9 steps / stages one / 1 two / 2 10 (process) reversible irreversible © UCLES 2021 Page 15 of 16

2(a)(i) any two from: 2 1 ref. to muscle fibre / sarcomere, contraction ; 2 active transport of (named), ion / molecule or active transport (of substance) against concentration gradient ; 3 movement of, vesicles / organelles, through cytoplasm / described ; 4 exocytosis of named substance ; 5 endocytosis / phagocytosis ; 6 spindle fibre / chromosome / chromatid, (movement) during, mitosis / meiosis ; 7 cilia / flagella, wafting / beating / AW ; I movement © UCLES 2021 Page 6 of 22 2(a)(ii) 150 750 2 correct working ; e.g. =750 then 0.2 24 or 150 6.25 =6.25 then 24 0.2 or 149.8 749 =749 then 0.2 24 31 ; 2(a)(iii) (respiration) oxidative phosphorylation ; 2 (photosynthesis) photophosphorylation / light dependent stage ; 2(b)(i) 1 reduces ATP synthesis / less ADP reacts with P ; 3 i any two from: 2 protons diffuse through thermogenin ; 3 proton gradient reduced / reduces concentration of H+ in intermembrane space ; 4 fewer protons pass through ATP synthase ; 2(b)(ii) any three from: 3 1 adrenaline binds to receptor on the cell surface membrane (of brown fat cells) ; 2 G-protein / adenyl(yl) cyclase, activated ; 3 ref. to cAMP / second messenger, (is formed) ; 4 ref. to enzyme cascade / signal amplification / activation of kinase / signalling cascade ; 5 activation of lipase by phosphorylation ; © UCLES 2021 Page 7 of 22

9(a) any nine from: 9 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 © UCLES 2021 Page 19 of 22 9(b) any six from: 6 1 aerenchyma ; 2 in stem and roots ; 3 help oxygen to, move / diffuse, to, roots / submerged parts ; 4 shallow roots ; 5 air (film) trapped on underwater leaves / described ; 6 greater internode growth or leaves or flowers grow above water level ; 7 (growth regulated by) gibberellin / ethene ; 8 anaerobic respiration, in roots / underwater / when submerged ; A alcoholic fermentation 9 tolerant to high ethanol (concentration) ; 10 ref. to ethanol / alcohol, dehydrogenase ; © UCLES 2021 Page 20 of 22

2(a)(i) active transport ; 1 2(a)(ii) correct working ; e.g. 2 945.5 31 × 30.5 = 945.5 then 2870 or 2870 30.5 = 92.58 then 31 92.58 32.94 / 32.9 / 33 ; 2(a)(iii) thermoregulation 1 or maintaining (constant), body / core, temperature ; I regulation 2(a)(iv) substrate-linked phosphorylation ; A substrate level phosphorylation 1 2(b) rest (RQ of 0.8) 4 1 a mix of respiratory substrates or lipids and, carbohydrates / proteins, are being respired ; 110 (RQ of 1.0) 2 respiratory substrate used is carbohydrate / carbohydrate respired (than at rest) ; A named carbohydrate e.g. glucose 200 (RQ of 1.2) 3 anaerobic respiration (also) occurring ; 4 reduced availability of oxygen or increased, production / release of CO ; 2 © UCLES 2021 Page 6 of 22 2(c) any three from: 3 1 ref. to oxygen debt ; oxygen needed to 2 convert lactate to pyruvate ; 3 convert lactate to glycogen ; 4 re-oxygenate, Hb / myoglobin ; 5 AVP ; e.g. to support a higher metabolic rate / ref. to EPOC © UCLES 2021 Page 7 of 22

6(a) carbon dioxide ; 1 6(b) any one from: 1 1 triose phosphate dehydrogenated ; 2 reduced NAD, made / released ; 6(c)(i) ( glycolysis ) + ( Krebs ) 2 (ATP + reduced NAD) + (ATP + reduced NAD + reduced FAD) (4 – 2) + (4 × 3) + 2 + (6 × 3) + (2 × 2) OR 2 + 12 + 2 + 18 + 4 ; 38 ; © UCLES 2021 Page 13 of 21 6(c)(ii) any two from: 2 1 ATP / energy, used to transport, pyruvate / reduced NAD / products of glycolysis, into (named part of) mitochondria ; 2 some protons leak from intermembrane space ; 3 some energy lost as heat ; 4 glucose may not be completely broken down / some intermediates are used in different metabolic processes ; 5 reduced NAD may be used for other (metabolic) reactions ; 6(d) any three from: 3 1 coenzymes ; 2 help / for, dehydrogenases / dehydrogenation (reactions) ; 3 ref. to glycolysis / link reaction / Krebs cycle ; 4 carry / transfer / transport / bring, hydrogens / H ; 5 to, ETC / inner mitochondrial membrane / crista(e) ; © UCLES 2021 Page 14 of 21 6(e) any three from: 3 1 less / no, energy (release from electron transfer / ETC) ; 2 less / no, chemiosmosis ; 3 fewer / no, protons, move / pumped, to intermembrane space ; 4 less (steep) / no, proton gradient ; 5 fewer / no, protons, move / diffuse, through ATP synth(et)ase ; 6 less / no, ATP synthesised ; Question Answer Marks

6(a)(i) any four from: 4 1 water soluble ; 2 (so) easily transported around the cell ; 3 (ATP) loses, P / phosphate group ; i 4 hydrolysed by ATPase / (ATP is) stable molecule ; 5 to release energy, immediately / in small packets or ref. to 30.5 kJ (mol–1) ; 6 can be, recycled / regenerated or ATP ⇄ ADP + P ; i 6(a)(ii) any two from: 2 1 unwinding DNA ; 2 activating (RNA) nucleotides ; 3 ref. to mRNA synthesis ; 4 peptide bond formation / joining amino acids ; 5 AVP ; e.g. post translation modification / amino acid activation / moving ribosomes along mRNA / movement of mRNA from nucleus © UCLES 2021 Page 17 of 24 6(b)(i) 2 statement letter the site of the Krebs Cycle A a phospholipid bilayer impermeable to H+ ions E / D the site of translation C ;; all correct = 2 marks 1 or 2 correct = 1 mark 6b(ii) (2 × π × 0.362 ) + (2 × π × 0.36 × 5.25) 2 or 2π × 0.36 (0.36 + 5.25) ; 12.7 or 12.68 or 12.69 ; accept 3.14 or π in workings 6(b)(iii) 1 (more cristae results in) more, ETC / (named) carrier proteins / ATP synthase ; 2 or (more cristae results in) more, oxidative phosphorylation / chemiosmosis / ATP synthesis ; 2 (because) cardiac muscle must undergo continuous contractions / AW ; © UCLES 2021 Page 18 of 24

6(a) carbon dioxide ; 1 6(b) any one from: 1 1 triose phosphate dehydrogenated ; 2 reduced NAD, made / released ; 6(c)(i) ( glycolysis ) + ( Krebs ) 2 (ATP + reduced NAD) + (ATP + reduced NAD + reduced FAD) (4 – 2) + (4 × 3) + 2 + (6 × 3) + (2 × 2) OR 2 + 12 + 2 + 18 + 4 ; 38 ; © UCLES 2021 Page 13 of 21 6(c)(ii) any two from: 2 1 ATP / energy, used to transport, pyruvate / reduced NAD / products of glycolysis, into (named part of) mitochondria ; 2 some protons leak from intermembrane space ; 3 some energy lost as heat ; 4 glucose may not be completely broken down / some intermediates are used in different metabolic processes ; 5 reduced NAD may be used for other (metabolic) reactions ; 6(d) any three from: 3 1 coenzymes ; 2 help / for, dehydrogenases / dehydrogenation (reactions) ; 3 ref. to glycolysis / link reaction / Krebs cycle ; 4 carry / transfer / transport / bring, hydrogens / H ; 5 to, ETC / inner mitochondrial membrane / crista(e) ; © UCLES 2021 Page 14 of 21 6(e) any three from: 3 1 less / no, energy (release from electron transfer / ETC) ; 2 less / no, chemiosmosis ; 3 fewer / no, protons, move / pumped, to intermembrane space ; 4 less (steep) / no, proton gradient ; 5 fewer / no, protons, move / diffuse, through ATP synth(et)ase ; 6 less / no, ATP synthesised ; Question Answer Marks

7(a) any seven from: 7 1 reduced, NAD / FAD ; 2 releases hydrogen / hydrogen splits into proton and electron ; 3 ref. to, inner mitochondrial membrane / cristae ; 4 electrons pass through, electron transport chain / ETC ; 5 ref. to energy release ; 6 protons transferred, through inner membrane / into intermembrane space ; 7 proton gradient established / high proton concentration in intermembrane space ; 8 protons diffuse through ATP synth(et)ase ; 9 ATP produced from ADP and Pi ; 10 ref. to chemiosmosis ; 11 oxygen acts as final electron acceptor (to form water) / described ; © UCLES 2022 Page 17 of 22 7(b) any four from: 4 1 population B produces more ATP (than population A) ; ora 2 production of ATP increases at a higher rate for population B (than for population A) ; ora 3 paired data quote ; 4 population B carries out, glycolysis / substrate-linked phosphorylation, and oxidative phosphorylation ; 5 population A carries out (only) glycolysis / respiration in anaerobic conditions / (ethanol) fermentation / substrate-linked phosphorylation or population A cannot carry out oxidative phosphorylation ; Question Answer Marks

3(a) anabolic / condensation / polymerisation ; 1 3(b) 1 to, phosphorylate / add phosphate to, glucose ; 2 and any one from: 2 stops glucose leaving the cell ; 3 activates glucose / makes glucose less stable ; 4 to make fructose (1,6) bi(s)phosphate ; 3(c) cytoplasm and mitochondrial matrix ; 1 © UCLES 2022 Page 9 of 19 3(d) any two from: 2 1 decarboxylated / loses carbon dioxide ; 2 dehydrogenated / oxidised / loses H ; 3 , 2C / acetyl, (group) joins coenzyme A to make acetyl coA ; 3(e) any three from: 3 mitochondria chloroplasts 1 oxidative phosphorylation photophosphorylation ; 2 inner mitochondrial membrane / crista(e) thylakoid membrane ; 3 reduced NAD / reduced FAD, give e– / H+ photolysis / water / PS1 / chlorophyll, give e– / H+ ; 4 (H+ ) intermembrane space (H+ ) thylakoid, space / lumen ; 5 oxygen, final, e– / H+, acceptor NADP final, e– / H+, acceptor ; 6 (makes) water / H O (makes) reduced NADP ; 2 © UCLES 2022 Page 10 of 19

3(a) any four from: 4 accept ora 1 pyruvate converted to, acetyl group / 2C group / acetyl CoA (in link reaction) ; 2 NAD needed (in link reaction) ; 3 (where) NAD becomes reduced ; 4 reduced NAD goes to ETC ; 5 ETC / oxidative phosphorylation, works if oxygen is present or oxygen is the final electron acceptor ; 6 (so) reduced NAD is oxidised / NAD is regenerated ; 3(b) any five from: 5 1 glycolysis ; 2 phosphorylation of glucose ; 3 splitting of fructose (1,6) bi(s)phosphate / AW ; 4 (into) two, triose phosphate / TP ; 5 (TP) oxidised / dehydrogenated, to pyruvate ; 6 net 2 ATP / 4 ATP, produced ; 7 (2) reduced NAD produced ; © UCLES 2022 Page 9 of 22

3(a) any two from: 2 substrate-linked (phosphorylation) ; A substrate level phosphorylation chemiosmosis / oxidative (phosphorylation) ; 3(b) any six from: 6 1 hydrogen / electron, carriers ; R hydrogen ions / hydrogen molecules 2 in glycolysis NAD becomes reduced ; 3 (so that) triose phosphate becomes, oxidised / dehydrogenated ; 4 in the link reaction NAD becomes reduced ; 5 (so that) pyruvate becomes, oxidised / dehydrogenated or for production of acetyl coenzyme A ; 6 in the Krebs cycle both NAD and FAD become reduced ; 7 to regenerate oxaloacetate ; 8 (deliver, hydrogen / H+ and e–), to inner mitochondrial membrane / to cristae / to ETC / for oxidative phosphorylation / for chemiosmosis ; 9 ref. to ATP production ; 10 ref. to recycling of, NAD / FAD ; © UCLES 2022 Page 10 of 23 3(c) any two from: 2 1 ref. to increase / decrease / control, of (rate of the) link reaction ; 2 allows build-up of acetyl CoA to be used in the Krebs cycle ; 3 enzyme becomes active again when, coenzyme A increases / ratio falls ; 4 allows more coenzyme A, to enter / return to, the link reaction ; A not enough CoA to enter the link reaction ora 5 AVP ; e.g. end product inhibition © UCLES 2022 Page 11 of 23

3(a)(i) any pair (max 2) from: 2 1 cristae / folds, let inner membrane expand ; 2 when water enters (matrix), by osmosis / down water potential gradient ; 3 inner membrane (relatively) impermeable to water ; 4 (so) water does not enter (matrix), by osmosis / down water potential gradient ; 5 inner membrane moves (H+) ions out of matrix ; 6 so less water enters (matrix), by osmosis / down water potential gradient ; 3(a)(ii) any three names plus explanations from: 3 1 pyruvate, for link reaction / to bind to coenzyme A / to make acetyl (CoA) / to make reduced NAD / be dehydrogenated ; 2 oxaloacetate to, accept acetyl / make citrate ; 3 citrate to, make reduced NAD / be dehydrogenated ; 4 enzymes to catalyse, link reaction / Krebs cycle ; 5 oxygen to, accept electrons / accept protons / form water ; 6 water as a, solvent / medium for reactions ; 7 DNA / RNA, to make (named) respiratory, enzymes / proteins ; © UCLES 2022 Page 8 of 19 3(a)(iii) any one from: 1 1 so H+, cannot move through / must move through ATP synthase ; 2 to maintain proton gradient ; 3(b)(i) any four from: 4 1 (H atoms) split into protons and electrons ; 2 electrons, flow / move, down ETC ; 3 (releases) energy used to move H+ to intermembrane space ; 4 more / build-up of, H+ / positive charge, in intermembrane space ; 5 (causes / sets up) proton / electrochemical, gradient ; 3(b)(ii) any two from: 2 1 (P) by facilitated diffusion or through a protein, channel / carrier ; i 2 P and H+ move together ; i 3 (as) H+ ions diffuse (through ATP synth(et)ase / to matrix) ; 3(b)(iii) 1 constant / sufficient / correct, supply / amount of, ADP / reactant ; 2 2 (so) ATP can continue to be made / so enough ATP can be made ; © UCLES 2022 Page 9 of 19

2(a)(i) any four from: 4 1 glycolysis ; 2 glucose to pyruvate ; 3 pyruvate to ethanal by, decarboxylation / CO removal ; 2 4 ethanal, reduced / hydrogenated, to ethanol ; 5 reduced NAD to NAD ; A regeneration of NAD 6 AVP ; e.g. ethanol / alcohol, dehydrogenase or pyruvate decarboxylase 2(a)(ii) any two from: 2 1 can survive (in absence of oxygen) ; 2 (as) ATP still produced (from glycolysis) ; 3 glycolysis can continue ; 4 as NAD recycled ; 2(b) any two from: 2 1 GM strain has higher (concentration of ethanol / ethanol production) or GM strain has steeper increase (in concentration of ethanol / ethanol production) ; ora 2 (both GM and non-GM) (concentration of ethanol / ethanol production) increases then levels off ; 3 comparative figs to support trend ; e.g. (mp1) (max concentration) for GM 19 g dm–3 and non-GM 1 g dm–3 (mp2) (levels off at) 18 g dm–3 for GM and 1 g dm–3 for non-GM © UCLES 2022 Page 6 of 19 2(c) any two from: 2 1 similar / same, concentration of starch hydrolysed ; 2 similar / same, concentration of glucose available (to yeast) ; 3 enzymes work at the same rate (in both methods) ; 4 AVP ; e.g. GM yeast cells produce more enzymes 2(d) any one from: 1 1 more (named) fuel or electricity needed ; 2 need to add enzymes ; 3 AVP ; e.g. (whole method) takes longer © UCLES 2022 Page 7 of 19

3(a)(i) any pair (max 2) from: 2 1 cristae / folds, let inner membrane expand ; 2 when water enters (matrix), by osmosis / down water potential gradient ; 3 inner membrane (relatively) impermeable to water ; 4 (so) water does not enter (matrix), by osmosis / down water potential gradient ; 5 inner membrane moves (H+) ions out of matrix ; 6 so less water enters (matrix), by osmosis / down water potential gradient ; 3(a)(ii) any three names plus explanations from: 3 1 pyruvate, for link reaction / to bind to coenzyme A / to make acetyl (CoA) / to make reduced NAD / be dehydrogenated ; 2 oxaloacetate to, accept acetyl / make citrate ; 3 citrate to, make reduced NAD / be dehydrogenated ; 4 enzymes to catalyse, link reaction / Krebs cycle ; 5 oxygen to, accept electrons / accept protons / form water ; 6 water as a, solvent / medium for reactions ; 7 DNA / RNA, to make (named) respiratory, enzymes / proteins ; © UCLES 2022 Page 8 of 19 3(a)(iii) any one from: 1 1 so H+, cannot move through / must move through ATP synthase ; 2 to maintain proton gradient ; 3(b)(i) any four from: 4 1 (H atoms) split into protons and electrons ; 2 electrons, flow / move, down ETC ; 3 (releases) energy used to move H+ to intermembrane space ; 4 more / build-up of, H+ / positive charge, in intermembrane space ; 5 (causes / sets up) proton / electrochemical, gradient ; 3(b)(ii) any two from: 2 1 (P) by facilitated diffusion or through a protein, channel / carrier ; i 2 P and H+ move together ; i 3 (as) H+ ions diffuse (through ATP synth(et)ase / to matrix) ; 3(b)(iii) 1 constant / sufficient / correct, supply / amount of, ADP / reactant ; 2 2 (so) ATP can continue to be made / so enough ATP can be made ; © UCLES 2022 Page 9 of 19

6(a)(i) D ; 1 6(a)(ii) D and C ; 1 6(b) any three from: 3 1 site of, link reaction / Krebs cycle ; 2 DNA / ribosomes, for production of proteins (used in respiration) ; 3 named example ; e.g. enzymes / coenzymes / electron carriers ; 4 production of, reduced FAD / reduced NAD, for oxidative phosphorylation ; 5 substrate-linked phosphorylation ; © UCLES 2023 Page 13 of 20 6(c) any four from: 4 process, stops / decreases, because: 1 no / fewer, electrons accepted by oxygen or oxygen is the final electron acceptor ; 2 no / fewer, electrons, enter / move along, electron transport chain / ETC or ETC stops ; 3 no /fewer, H+ pumped into intermembrane space or no / less steep, proton gradient ; 4 no / less, chemiosmosis ; 5 reduced NAD / reduced FAD, not oxidised / or NAD / FAD, not recycled ; 6 no / less, ATP produced ; 7 AVP ; e.g. no / less, pyruvate enters mitochondrion. © UCLES 2023 Page 14 of 20

9(a) 1 environmental ; 2 2 discontinuous ; 9(b) any five from: 5 coenzyme A: 1 accepts / binds to / transfers, acetyl (group) ; 2 acetyl / 2C fragment, + oxaloacetate  citrate ; 3 (joins) link reaction and Krebs cycle ; NAD / FAD: 4 transfer / transport / carry / accept / reduced by, H+ and e– / H (atoms) / hydrogen (atoms) ; 5 ref. dehydrogenation (reactions) / dehydrogenase (enzymes) ; 6 transport, to cristae / to inner mitochondrial membrane / to ETC / for oxidative phosphorylation ; 7 NAD (accepts H) in glycolysis and link reaction and Krebs cycle ; © UCLES 2023 Page 16 of 17

1(a)(i) any one from: 1 glucose is activated / made reactive ; becomes unstable ; cannot leave cell ; energy level increased ; concentration gradient maintained ; 1(a)(ii) any one from: 1 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 © UCLES 2023 Page 7 of 25 1(b) any three from: 3 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: 3 1 decarboxylation ; A description 2 dehydrogenation / oxidation, (of pyruvate) ; A description 3 reduced NAD produced ; 4 formation of, acetyl coenzyme A / acetyl CoA ; © UCLES 2023 Page 8 of 25

1(a) P – citrate A citric acid 3 Q – NAD / NAD+ R – reduced NAD / NADH A NADH 2 S – carbon dioxide / CO 2 T – FAD U – reduced FAD / FADH ;;; 2 6 correct = 3 marks 5/4 correct = 2 marks 3/2 correct = 1 mark 1(b) any two from: 2 1 transfer of phosphate group to ADP / ADP phosphorylated / ADP + P → ATP ; i 2 substrate-linked phosphorylation ; A substrate-level phosphorylation R if oxidative phosphorylation 3 enzyme (catalysed reaction) ; © UCLES 2023 Page 6 of 24 1(c) any four from: 4 1 small / water-soluble, so can move around cell ; 2 loss of phosphate / hydrolysis, leads to energy release ; 3 (release energy) immediately / in small packets or ref. 30.5 kJ (mol–1) ; 4 can be, recycled / regenerated or ATP ⇆ ADP + Pi ; 5 link between energy-yielding and energy-requiring reactions / AW ; 6 high turnover / described ; 7 ref to ATPase ; © UCLES 2023 Page 7 of 24

5(a) highest: malic acid ; 2 lowest: oleic acid ; 5(b) any five from: 5 similarities: 1 use pyruvate ; 2 occur in, cytoplasm / cytosol ; 3 make / regenerate, NAD ; 4 redox reaction ; differences: 5 lactate / lactic acid, made in mammals and ethanol in yeast ; 6 one step in mammals and two steps in yeast ; 7 carbon dioxide made in yeast (not in mammals) ; 8 reversible in mammals and irreversible in yeast ; Question Answer Marks

1(a) A: carbon dioxide / CO ; 3 2 B: reduced NAD / NADH and C: NAD / NAD+ ; D: ethanal ; 1(b) any three from: 3 1 (recycles / produces) NAD ; I ref. to reduced NAD produced ; 2 ref. to glycolysis ; 3 ref. to ATP (produced) ; 4 by substrate-linked phosphorylation ; 1(c) any three from: 3 1 aerenchyma provides oxygen for aerobic respiration ; 2 high concentration of ethanol dehydrogenase / high tolerance for ethanol, allows (higher rate of), ethanol fermentation / anaerobic respiration ; 3 fast growth / grow tall, so leaves, out of water / exposed to air ; 4 AVP ; e.g. ridges in submerged leaves to trap air Question Answer Marks

5(a) highest: malic acid ; 2 lowest: oleic acid ; 5(b) any five from: 5 similarities: 1 use pyruvate ; 2 occur in, cytoplasm / cytosol ; 3 make / regenerate, NAD ; 4 redox reaction ; differences: 5 lactate / lactic acid, made in mammals and ethanol in yeast ; 6 one step in mammals and two steps in yeast ; 7 carbon dioxide made in yeast (not in mammals) ; 8 reversible in mammals and irreversible in yeast ; Question Answer Marks

6(a) absorb carbon dioxide (produced by peas) ; 1 6(b) any two from: 2 1 idea of repeatability ; 2 check to see how consistent the results are / the more consistent the results, the more valid the results / carry out a (named) statistical test or measure / calculate standard deviation / calculate standard error ; 3 a control respirometer / described ; e.g. with glass beads instead of peas 4 ref. to checking variables (other than temperature) ; e.g. volume of germinating peas / volume / concentration of KOH 6(c) acclimatisation / equilibration / AW ; 1 © Cambridge University Press & Assessment 2024 Page 12 of 21 6(d) 5 points plotted accurately ; 2 smooth curve drawn linking all plotted points / curve of best fit ; R extrapolation 6(e) any three from: 3 1 ref to enzymes ; 2 (as temperature increases) kinetic energy increases ; 3 (so) rate increases, due to more enzyme-substrate complexes formed (in same time) or (so) rate increases, due to higher, proportion / frequency, of, successful / effective, collisions ; 4 (rate decreases after 30 °C) due to denaturation of enzymes ; 5 further detail ; e.g. active site shape change / ref. optimum temperature Question Answer Marks

1(a) 3 stage of respiration letter glycolysis B link reaction D Krebs cycle D oxidative phosphorylation C ;;; 3 marks if all four letters are correct 2 marks if three letters are correct 1 mark if one or two letters are correct 1(b) any four from: 4 1 oxygen is the, final / last / terminal, electron acceptor ; 2 electron transport chain / ETC, stops ; 3 less / no, protons / H+ / hydrogen ions, move, into intermembrane space / across inner mitochondrial membrane ; 4 less / no, proton / electrochemical, gradient ; 5 less / no, protons move through ATP synthase ; 6 less / no, recycling / regeneration, of, NAD / FAD ; 1(c) any three from: 3 1 lactate dehydrogenase ; 2 less / no, pyruvate → lactate ; 3 (so) less / no, NAD, regenerated / recycled ; 4 (so) less / no, triose phoshate / TP, → pyruvate ; 5 (so) less / no, ATP from substrate, linked / level, reactions / phosphorylation (in glycolysis) ; © Cambridge University Press & Assessment 2024 Page 6 of 15

6(a) an arrow through phospholipid layer in outer membrane and an arrow through phospholipid layer in inner membrane ; 1 R arrows through proteins or A, B, C or D 6(b) 1 D = ATP synthase / ATP synthetase ; R ATPase 7 2 A, B and C = ETC / electron transport chain / electron carriers / electron acceptors ; plus any five from: role of, ETC proteins / A, B and C 3 electrons travel along ETC ; 4 energy released ; 5 (use energy released) to pump / actively transport, H+ / protons, into intermembrane space ; 6 increases concentration of H+ / protons (in intermembrane space) / creates proton gradient ; role of D 7 H+ / protons, diffuse through, ATP synthase / D ; 8 (from intermembrane space) to matrix ; 9 synthesis of ATP from ADP and Pi ; 10 chemiosmosis ; © Cambridge University Press & Assessment 2024 Page 13 of 20 6(c) any three from: 3 1 (named) enzyme for, Krebs cycle / link reaction ; 2 ETC proteins / cytochromes / electron carriers / electron acceptors / A / B / C ; 3 ATP synthase / D / described ; 4 membrane / channel / transport / carrier / structural, proteins ; 5 (make) tRNA / rRNA / ribosomes ; Question Answer Marks

8(a) any four from: 4 outer / inner membranes 1 allow entry of, oxygen for oxidative phosphorylation / pyruvate for link reaction ; I Krebs cycle 2 allow exit of carbon dioxide from, Krebs cycle / link reaction ; 3 compartmentalisation / described ; inner membrane 4 (location of) ETC to release energy to pump protons into intermembrane space ; 5 (location of) ATP synthase for production of ATP ; 6 cristae / infoldings, to increase surface area for many, ETCs / ATP synthases ; 7 impermeable to, hydrogen ions / protons, to maintain proton gradient or impermeable to, hydrogen ions / protons, to maintain, high H+ concentration in intermembrane space ; 8 site of, oxidative phosphorylation / chemiosmosis ; 8(b)(i) any two from: 2 1 ref. to cells, metabolic rate / energy needs ; 2 in cells about to undergo, mitosis / cell division ; 3 AVP ; e.g. to replace damaged mitochondria 8(b)(ii) hydrolysed / bond broken, (to release energy) 1 or G proteins bind to GTP rather than to ATP ; 8(c) 1 degraded / broken down by, lysosomes / hydrolytic enzymes ; 2 2 components of breakdown / AW, used to produce new mitochondria ; © Cambridge University Press & Assessment 2024 Page 17 of 20

3(a) 4 event stage G LR KC OP catabolism ✓ ✓ ✓  ; coenzyme is reduced or oxidised ✓ ✓ ✓ ✓ ; a coenzyme forms a covalent bond with a  ✓   ; respiratory intermediate carbon dioxide is released  ✓ ✓  ; 3(b)(i) any four from: 4 1 (RQ =) ratio of carbon dioxide (exhaled) to oxygen (inhaled) ; 2 air flow meter measures oxygen inhaled ; 3 carbon dioxide sensor measures concentration of CO exhaled ; 2 4 carbohydrate RQ = 1 ; 5 lipid RQ = 0.7 ; 3(b)(ii) any three from: 3 1 lipid has higher energy (value) OR carbohydrate 15–17 kJ g-1 and lipid 37–40 kJ g-1 ; 2 more, hydrogen (atoms) / C-H bonds, in lipid ; 3 more reduced, NAD / FAD ; 4 greater proton gradient / more protons in intermembrane space / more protons pass through ATP synth(et)ase ; © Cambridge University Press & Assessment 2024 Page 8 of 15

6(a)(i) redox ; 1 6(a)(ii) blue to colourless ; 1 6(b)(i) any two from: 2 1 volume / mass / concentration, of yeast suspension ; 2 volume / mass / concentration, of glucose (solution) ; 3 volume / concentration, of DCPIP ; 4 AVP ; e.g. time when DCPIP is added / pH 6(b)(ii) any three from: 3 1 the less time taken (for DCPIP) to change colour the higher the rate of respiration ; ora rate increases up to 40 °C 2 due to increase in, kinetic energy / KE ; 3 due to more enzyme-substrate complexes formed or due to more (successful / effective) collisions between enzymes and substrates or more enzyme catalysed reactions ; rate decreases after 40 °C 4 due to denaturation of (named respiration) enzyme ; 5 further detail ; e.g. active site shape change / optimum temperature 40 °C © Cambridge University Press & Assessment 2024 Page 12 of 19

3(a) 4 event stage G LR KC OP catabolism ✓ ✓ ✓  ; coenzyme is reduced or oxidised ✓ ✓ ✓ ✓ ; a coenzyme forms a covalent bond with a  ✓   ; respiratory intermediate carbon dioxide is released  ✓ ✓  ; 3(b)(i) any four from: 4 1 (RQ =) ratio of carbon dioxide (exhaled) to oxygen (inhaled) ; 2 air flow meter measures oxygen inhaled ; 3 carbon dioxide sensor measures concentration of CO exhaled ; 2 4 carbohydrate RQ = 1 ; 5 lipid RQ = 0.7 ; 3(b)(ii) any three from: 3 1 lipid has higher energy (value) OR carbohydrate 15–17 kJ g-1 and lipid 37–40 kJ g-1 ; 2 more, hydrogen (atoms) / C-H bonds, in lipid ; 3 more reduced, NAD / FAD ; 4 greater proton gradient / more protons in intermembrane space / more protons pass through ATP synth(et)ase ; © Cambridge University Press & Assessment 2024 Page 8 of 15

1(a) all three correct = 1 mark ; 1 energy value / kJ g–1 type of respiratory substrate approximately 17 approximately 37 carbohydrate ✓ lipid ✓ protein ✓ 1(b)(i) respirometer ; 1 1(b)(ii) to, absorb / remove, carbon dioxide ; 1 1(c)(i) 3 ; 1 1(c)(ii) 1.33 ; ecf from (b)(i) 1 1(d)(i) any three from: 3 1 RQ value falls ; 2 data quote ; RQ = 0.9 at, start of torpor / 8:00 or maximum RQ = 0.98 and RQ = 0.75 at, end of torpor / 17:12 3 respires / metabolises, lipid / protein ; 4 AVP ; e.g. running out of available, carbohydrate / glycogen © Cambridge University Press & Assessment 2025 Page 5 of 19 1(d)(ii) any two from: 2 1 during, winter / cold weather, when food is limited / to conserve energy / to reduce heat loss / AW ; 2 during, summer / hot weather / dry conditions, to, conserve water / prevent overheating ; 3 to avoid predation ; 4 AVP ; e.g. factor plus reason Question Answer Marks

8(a) decarboxylation ; 2 dehydrogenation / oxidation ; © Cambridge University Press & Assessment 2025 Page 16 of 19 8(b) any four from: 4 1 reduces activity of citrate synthase or activity of citrate synthase is higher without succinyl-coA than with succinyl-coA ; 2 comparative data quote ; 3 succinyl-coA binds to citrate synthase active site ; 4 succinyl-coA acts as a competitive inhibitor / described ; 5 slows down Krebs cycle ; 6 prevents build up / reduces production, of, citrate / intermediates ; 7 AVP ; 8(c) any four from: 4 1 hydrogen carrier / reduced ; 2 in, link reaction / Krebs cycle ; 3 moves to, inner mitochondrial membrane / cristae ; 4 releases hydrogen (atoms) ; A protons and electrons 5 for use in, oxidative phosphorylation ; 6 NAD, oxidised / recycled ; © Cambridge University Press & Assessment 2025 Page 17 of 19

1(a) any two from: 2 glucose (phosphate) ; fructose (phosphate / bisphosphate) ; triose phosphate ; (named) fatty acid / keto-acid ; glycerol ; amino acid ; 1(b) any four from: 4 1 breaks down / hydrolyses to, ADP / AMP, and Pi ; 2 releases, energy / 30.5 kJ mol-1 ; 3 reversible reaction / high turnover / can be regenerated ; 4 small / soluble, so can, diffuse / move (freely), in cell ; 5 AVP ; 1(c) substrate-linked / substrate-level (phosphorylation) ; 1 1(d)(i) oxygen ; 1 1(d)(ii) presence of oxygen: 3 1 (ATP yield) increases / is higher ; plus any two from: 2 oxygen acts as final, electron / proton, acceptor ; 3 oxidative phosphorylation / chemiosmosis (occurs) ; 4 energy from, reduced NAD / reduced FAD / electron transport chain ; 5 proton gradient / H+ → into intermembrane space ; 6 ATP made in Krebs cycle ; © Cambridge University Press & Assessment 2025 Page 8 of 17

2(a) any four from: 4 1 sodium hydroxide absorbs, carbon dioxide / CO , released by, woodlice / respiration ; 2 2 oxygen / O , taken in reduces pressure (in boiling tube) ; 2 3 drop of liquid moves towards, boiling tube / bung / woodlice / left ; 4 measure, distance / length, moved by drop, in set time ; 5 rate = distance divided by time ; 6 detail of calculation of volume of O used ; 2 2(b) rate at 5 °C: 1 lower / slower and less / lower, kinetic energy or fewer enzyme-substrate, collisions / complexes or fewer, enzyme-catalysed / respiration / glycolysis / link reaction / Krebs cycle, reactions ; Question Answer Marks

1(a)(i) 2 ; 1 1(a)(ii) pumps / actively transports, protons / hydrogen ions, into intermembrane space ; 2 ref. to proton gradient ; 1(a)(iii) any three from: 3 1 ATP synthase ; 2 protons / hydrogen ions, move (from intermembrane space) to matrix ; 3 by facilitated diffusion ; 4 ATP synthesised from ADP + Pi ; A ADP is phosphorylated to ATP 5 ref. to chemiosmosis ; © Cambridge University Press & Assessment 2025 Page 8 of 25 1(b) any four from: 4 1 electron transport chain / ETC, stops / reduced ; 2 oxygen does not act as (final) electron acceptor ; 3 no / less , protons pumped into intermembrane space or no / less steep, proton gradient ; 4 build-up of, reduced NAD / reduced FAD or no / less, reduced NAD / reduced FAD, oxidised / recycled or no / less, NAD / FAD, regenerate / recycled ; 5 no / less, ATP production or no / fewer, protons pass through ATP synthase ; 6 Krebs cycle / link reaction / oxidative phosphorylation, stops / reduced ; 7 ref. to glycolysis / anaerobic respiration / lactate produced / ethanol produced / substrate level phosphorylation ; © Cambridge University Press & Assessment 2025 Page 9 of 25

10(a) any four from: 4 during – increase in lactate concentration 1 (initially) lactate concentration low due to aerobic respiration ; 2 no / less, oxygen available so (increase in) anaerobic respiration ; 3 pyruvate, reduced / converted, to lactate ; after – decrease in lactate concentration 4 (more) oxygen available so aerobic respiration occurs ; 5 lactate, oxidised / converted, to pyruvate ; 6 idea that lactate is processed by liver ; 7 AVP ; e.g. ref. to oxygen debt / EPOC 10(b) any three from: 3 1 (captive) breeding programs / described / frozen zoos ; 2 marine reserves / protected areas ; 3 ban on hunting / trade, (of seals) ; 4 ref. to education / awareness ; 5 research ; 6 reduce, ocean / sea, pollution / described ; 7 reduce fishing ; 8 reduce climate change ; © Cambridge University Press & Assessment 2025 Page 25 of 25

1(a) A – GLUT / carrier ; I channel 3 B – glycolysis ; C – intermembrane space ; A intermembranal R inner membrane 1(b) any four from: 4 1 (pyruvate) decarboxylation / decarboxylase / carbon dioxide released ; 2 (pyruvate) dehydrogenation / dehydrogenase / oxidation ; 3 formation of, acetyl group / acetate ; 4 reduced NAD produced / described ; 5 acetyl group / acetate, combines with coenzyme A or formation of acetyl CoA ; 1(c) any three from: 3 1 little / no, link reaction / Krebs cycle / oxidative phosphorylation ; 2 ATP, mostly / only, produced by, glycolysis / process B / substrate-linked phosphorylation ; 3 (so) less ATP produced ; 4 anaerobic respiration / production of lactate ; © Cambridge University Press & Assessment 2025 Page 8 of 20

10(a)(i) molecules / moles / volume, carbon dioxide produced 1 molecules / moles / volume, oxygen taken in ; 10(a)(ii) 25 ; 1 10(a)(iii) 0.72 ; 1 A ecf 18 divided by their answer to 10(a)(ii) © Cambridge University Press & Assessment 2025 Page 26 of 27 10(b) any four from: 4 1 RQ (initially) at 1.0 as, carbohydrates / (named) sugar, respired / metabolised ; 2 RQ decreases (over time) as, carbohydrates / (named) sugar, running out / used up ; 3 RQ decreases (over time) as a mixture of carbohydrate and lipid respired ; I proteins 4 RQ at, 0.65 / 0.7, as, fatty acids / fats / lipids, respired (as main respiratory substrate) or from 120 min onwards, fatty acids / fats / lipids, respired (as main respiratory substrate) ; 5 data quote ; RQ of 1.0 at 40 min plus any RQ value at any other time Time after RQ ratio feeding / min 40 1.0 80 0.75 120 0.7 160 0.65 200 0.7 240 0.7 © Cambridge University Press & Assessment 2025 Page 27 of 27

7(a) any three from: 3 1 breaks down / hydrolyses to / converted to, ADP / AMP, and Pi ; 2 releases energy / energy donor ; 3 reversible reaction / high turnover / can be regenerated ; 4 small / soluble, so can, diffuse / move (freely), in cell ; 5 AVP ; 7(b) any six from: 6 1 ETC / electron flow, less / stops ; 2 no / less, energy, available / released / supplied (from electron flow) ; 3 no / fewer, H+ ions / protons, pumped to intermembrane space ; 4 no / smaller, H+ / proton, gradient ; 5 no / fewer, protons diffuse through ATP synthase ; 6 no / fewer, electrons reach, last carrier / end of chain ; 7 no / fewer, electrons can react with oxygen to form water ; 8 (oxidised) NAD not regenerated / lack of NAD ; 9 no / less, glycolysis / link reaction / Krebs cycle ; 10 AVP ; © Cambridge University Press & Assessment 2025 Page 15 of 18

7(a) any three from: 3 1 breaks down / hydrolyses to / converted to, ADP / AMP, and Pi ; 2 releases energy / energy donor ; 3 reversible reaction / high turnover / can be regenerated ; 4 small / soluble, so can, diffuse / move (freely), in cell ; 5 AVP ; 7(b) any six from: 6 1 ETC / electron flow, less / stops ; 2 no / less, energy, available / released / supplied (from electron flow) ; 3 no / fewer, H+ ions / protons, pumped to intermembrane space ; 4 no / smaller, H+ / proton, gradient ; 5 no / fewer, protons diffuse through ATP synthase ; 6 no / fewer, electrons reach, last carrier / end of chain ; 7 no / fewer, electrons can react with oxygen to form water ; 8 (oxidised) NAD not regenerated / lack of NAD ; 9 no / less, glycolysis / link reaction / Krebs cycle ; 10 AVP ; © Cambridge University Press & Assessment 2025 Page 15 of 18

9(a) 1 NAD ; 2 2 coenzyme A ; 9(b) any three from: 3 1 enzyme activity decreases over time at both concentrations (of hydrogen peroxide) ; 2 activity decreases, more / faster / at a greater rate, at high(er) H O concentration 2 2 or enzyme less active with, with high(er) H O concentration ; 2 2 3 paired data quote ; 4 H O , acts as an inhibitor / inhibits enzyme activity ; 2 2 © Cambridge University Press & Assessment 2025 Page 15 of 17 9(c) any four from: 4 1 energy is used to pump, protons / H+, into intermembrane space ; 2 proton gradient (formed) ; 3 protons diffuse through ATP synthase ; 4 ATP produced from ADP and Pi ; 5 oxygen accepts electrons to form water ; 6 ref. to chemiosmosis ; 9(d) any three from: 3 1 respiration in anaerobic conditions ; 2 produces lactate ; 3 need oxygen, to oxidise lactic acid to CO and H O / 2 2 for breakdown of lactic acid in Krebs cycle plus oxidative phosphorylation / (for ETC) to make extra ATP ; 4 ATP used for lactate → glucose / glycogen ; 5 idea of re-paying oxygen debt ; © Cambridge University Press & Assessment 2025 Page 16 of 17

8(a) A = active transport ; 3 B = anabolism / anabolic (reaction) / polymerisation / bond formation / condensation (reaction) ; C = photoactivation / light activation / photo-ionisation ; 8(b) 1 protons diffuse through ATP synth(et)ase ; 2 2 protons are pumped into intermembrane space / proton gradient formed / ADP + inorganic phosphate ; 8(c) 222.4 ; ; allow 1 mark for: © Cambridge University Press & Assessment 2026 Page 21 of 25  3 1 7 7 . 8 . 0   1 0 0 2 or not to one decimal place

9(a) 1 oxygen concentration decreases (with time) ; 4 2 oxygen concentration becomes constant when nitric oxide is added ; 3 oxygen concentration remains constant for longer with each addition ; max three for explanation: 4 (nitric oxide may) prevent oxygen uptake ; 5 (nitric oxide may) inhibit, pyruvate entering mitochondrion / the link reaction / Krebs cycle / ETC / oxidative phosphorylation ; 6 so oxygen cannot act as final electron acceptor ; 7 inhibits aerobic respiration ; 8 effect of nitric oxide is temporary ; 9(b) any four from: 4 mp muscle yeast 1 lactic acid / lactate ethanol ; 2 one-step process two-step process ; A from equation A from equations 3 reversible irreversible ; 4 no carbon dioxide produced / carbon dioxide produced / ; no decarboxylation decarboxylation 5 lactate dehydrogenase ethanol / alcohol, dehydrogenase ; © Cambridge University Press & Assessment 2026 Page 22 of 25 9(c) any three from: 3 1 aerenchyma in, stems / roots, to provide oxygen to submerged parts ; 2 tall stems / fast growth of stems / greater internode growth, to hold, leaves / flowers, above water / exposed to air ; 3 roots have, ethanol / alcohol, dehydrogenase or roots are tolerant to ethanol for, ethanol fermentation / anaerobic respiration ; 4 ridges in submerged leaves to trap air ; © Cambridge University Press & Assessment 2026 Page 23 of 25

1(a) 5 stage location in the products of this stage cell IGNORE numbers glycolysis cytoplasm pyruvate ALLOW NADH / red NAD / NAD red, for ‘reduced NAD’ and IGNORE NADH+ / NADH ATP 2 and reduced NAD ; ALLOW 1 mark if ‘matrix’ alone stated for both link and Krebs link mitochondrial carbon dioxide ALLOW 1 mark if ‘mitochondrion / mitochondria’ alone reaction matrix ; and stated for both acetyl co(enzyme) A ALLOW 2 marks if ‘matrix’ alone stated for one but and ‘mitochondrion / mitochondrial, matrix’ stated for the other reduced NAD ; Krebs mitochondrial carbon dioxide IGNORE oxaloacetate / water / GTP (for Krebs cycle) cycle matrix ; and ATP ALLOW FADH / red FAD / FAD red, for ‘reduced FAD’ and 2 IGNORE FADH reduced, NAD / FAD ; 1(b) 1 hydrogen ion / H+ / proton ; 3 1 ALLOW ‘hydrogen / H’ alone 2 thylakoid (membrane) ; 1 DO NOT ALLOW hydrogen molecule / H 2 3 facilitated diffusion ; 2 DO NOT ALLOW thylakoid space © Cambridge University Press & Assessment 2026 Page 8 of 23 Trace ID: PC-791D658355 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/41 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

9(a) any two from: LIST RULE APPLIES 2 IGNORE phosphorylation 1 make, nucleic acid / polynucleotide / DNA / RNA ; 1 ALLOW DNA replication / transcription 2 make (named), peptide / polypeptide / protein ; 2 ALLOW protein synthesis / translation 3 make, lipid / triglyceride / phospholipid (from smaller units); 3 ALLOW lipogenesis 4 make (named), disaccharide / polysaccharide (from 4 ALLOW glycogenesis smaller units) ; 5 Calvin cycle ; 5 ALLOW regenerate RuBP 6 AVP ; 6 e.g. join amino acid to tRNA 9(b)(i) 1 growth / larger / more cells (to support) ; 2 2 mobile / moves / locomotion / swims / muscle contraction ; 3 AVP ; 3 e.g. nerve impulses / nervous system activity ref. reproduction 9(b)(ii) substrate-level / substrate-linked, phosphorylation ; 2 oxidative phosphorylation / chemiosmosis ; 9(c)(i) 1430 / 2020 (= 0.7079) ; 2 answer: 0.71 ; ECF for answer rounded to 2 s.f. from incorrect working 9(c)(ii) A ; 1 © Cambridge University Press & Assessment 2026 Page 21 of 23 Trace ID: PC-791D658355 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/41 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

9(a) any three from: 4 less hexokinase so: 1 less glucose, phosphorylated / activated ; 2 less glucose diffuses into cell (as less steep concentration gradient) ; 3 less, glycolysis / formation of pyruvate ; 4 less ATP formed ; 5 loss of red blood cells / anaemia / less oxygen transport ; plus symptom 6 fatigue / shortness of breath / faint / feeling dizzy ; 9(b) any four from: 4 1 acetyl CoA / acetyl group / acetate / 2C fragment, combines with oxaloacetate to form citrate ; 2 decarboxylation / carbon dioxide produced ; 3 dehydrogenation / oxidation (of named intermediate) ; 4 reduced, NAD / FAD, produced ; 5 ATP produced by substrate-linked phosphorylation ; 6 oxaloacetate, recycled / regenerated / formed again ; © Cambridge University Press & Assessment 2026 Page 20 of 23 Trace ID: PC-913B5F5E92 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/42 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 9(c) any three from: 3 1. pyruvate / (net 2) ATP, formed by glycolysis or substrate-linked phosphorylation occurs in glycolysis ; 2 pyruvate reduced by reduced NAD ; Reject pyruvate is dehydrogenated 3 lactate formed / lactate fermentation ; A lactic acid 4 NAD, regenerated / recycled or reduced NAD oxidised (to NAD) / reduced NAD converted to NAD ; 5 AVP ; e.g. lactate dehydrogenase © Cambridge University Press & Assessment 2026 Page 21 of 23 Trace ID: PC-913B5F5E92 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/42 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

9(a) any four from: 4 structure function in respiration outer permeable for (diffusion of), oxygen / carbon ; 1 membrane dioxide / pyruvate / reduced NAD 2 site of, chemiosmosis / oxidative phosphorylation ; (forms) cristae / is folded, to provide, large / increased, ; inner surface area membrane 3 or (has) many, electron transport chains / ETCs / electron carriers / ATP synthase (molecules) intermembrane ref. to setting up proton gradient / high concentration of ; 4 space protons 5 matrix site of (enzymes in) the, Krebs cycle / link reaction ; 6 DNA codes for, (named) proteins / ribosomes / RNA ; 9(b) any three from: 3 1 idea that more active the cell means more mitochondria ; 2 idea that heart muscle (cell) contraction needs lots of ATP ; 3 liver cell carries out, glycogenolysis / glycogenesis / gluconeogenesis / deamination / detoxification, so needs ATP ; 4 idea that red blood cells need room for haemoglobin ; © Cambridge University Press & Assessment 2026 Page 18 of 20 Trace ID: PC-C51CA5D8F2 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/43 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 9(c) any three from: 3 1 glucose phosphorylated by ATP to form fructose (1,6-)bisphosphate ; 2 fructose (1,6-)bisphosphate splits into two molecules of, triose phosphate / TP ; R hydrolysed 3 triose phosphate / TP, oxidised to pyruvate ; A dehydrogenated 4 ATP / reduced NAD, produced ; Question Answer Marks

10(a) any four from: 4 1 glucose phosphorylated (to form fructose (1,6) bisphosphate) ; 2 fructose (1,6) bisphosphate splits ; 3 (into) two, triose phosphate / TP ; 4 (triose phosphate / TP) oxidised to pyruvate ; 5 ATP / reduced NAD, produced ; 10(b) any four from: 4 1 fewer / no, acetyl groups combine with coenzyme A or less / no, acetyl CoA formed or decrease in rate of / stops, link reaction ; 2 fewer / no, acetyl CoA / acetyl group / acetate / 2C fragment, to combine with oxaloacetate ; 3 decrease in rate of / stops, Krebs cycle ; 4 decrease in / stops, production of, reduced NAD / reduced FAD ; 5 (so) fewer / no, electrons pass along ETC ; 6 decrease in / stops, oxidative phosphorylation / substrate-linked phosphorylation / ATP production ; © Cambridge University Press & Assessment 2026 Page 21 of 22 Trace ID: PC-C13BFDE7F5 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/44 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 10(c) labels to: 4 A – ATP synthase ; B – inner membrane ; C – intermembrane space ; D – left hand carrier ; © Cambridge University Press & Assessment 2026 Page 22 of 22 Trace ID: PC-C13BFDE7F5 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/4a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/44 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/