Photosynthesis

4(a)(i) 565nm ; 1 4(a)(ii) 1 phycoerythrin does not absorb light above 590–600 (nm) ; 2 A suitable value for absorption that answer the question 2 (but) photosynthesis still takes place (above 590–600 nm) ; A suitable value for absorption that answer the question © UCLES 2021 Page 11 of 22 4(a)(iii) any two from: 2 1 accessory pigment ; 2 absorbs light energy (up to 595 nm) ; R trap / capture 3 (and) passes it to, primary pigment / reaction centre / chlorophyll a ; 4(b)(i) chromatography ; 1 4(b)(ii) any three from: 3 1 calculate R value(s) ; f 2 compare R values of pigments (in red algae and green plant) ; f 3 find pigment present (on chromatogram) from red algae but absent from green plant or R value of phycoerythrin will not be the same as Rf values of pigments in green leaves ; f 4 identify pigment using reference values (to confirm it is phycoerythrin) ; © UCLES 2021 Page 12 of 22

1(a)(i) any two from: 2 1 absorb / harvest / capture / trap, light / photons ; 2 (to) excite electrons ; 3 (for, cyclic / non-cyclic) photophosphorylation / electron transport chain ; 4 accessory pigment passes energy to, primary pigment / reaction centre ; 5 (pigments) form a, light harvesting cluster / photosystem / PSI / PSII ; 1(a)(ii) thylakoid membrane(s) / granum / grana / lamella(e) ; 1 1(a)(iii) chromatography ; 1 1(b)(i) 1 (from 0.25) to 1.00 (mol dm–3), concentration / CO , is limiting factor 3 2 or at / >, 1.00 (mol dm–3), concentration / CO , no longer limiting factor ; 2 2 at / >, 1.00 (mol dm–3), light intensity / temperature, is limiting factor ; 3 CO , needed / used, for Calvin cycle / for light independent stage 2 or CO ,reacts with / fixed by, RuBP ; 2 1(b)(ii) little / no, photosynthesis ; 2 (aerobic) respiration uses oxygen ; 1(b)(iii) any three from: 3 1 to control a variable / to ensure a fair test / so CO is the only variable ; 2 2 low, temperature / kinetic energy, decreases, rate / reaction / photosynthesis / O production / O increase ; 2 2 3 low, temperature / kinetic energy, decreases, (named) enzyme-substrate, collisions / complexes ; 4 low(er) temperature, is a limiting factor / may limit rate ; 5 high, temperature / kinetic energy, decreases, rate / reaction / photosynthesis / O production / O increase ; 2 2 6 high, temperature / kinetic energy, denatures (named) enzyme(s) ; 7 high / increased, temperature, causes / increases, photorespiration ; © UCLES 2021 Page 6 of 16

5(a)(i) mark first two answers 2 ATP ; reduced NADP ; A NADPH 5(a)(ii) any two from: 2 1 an accessory pigment ; 2 absorb, light (energy) / photons ; A harvest I trap / capture 3 pass on energy to, primary pigment / chlorophyll a / reaction centre ; 4 AVP ; e.g. idea of extending the range of light wavelengths absorbed / absorbs wavelengths not absorbed by primary pigment © UCLES 2021 Page 12 of 22 5(b) 100 ; 1 5(c)(i) 1 0 – 400 ; A up to 400 I units 3 any two from: 2 temperature / concentration of carbon dioxide, becomes the limiting factor ; 3 (at a lower than optimum temperature) less kinetic energy so fewer collisions between rubisco and CO 2 or a lower temp will limit the rate of (named) enzyme-controlled reactions ; 4 (with a lower than optimum CO concentration) less fixation of CO / AW ; 2 2 5 all, enzymes / processes, in photosynthesis, already at, highest rate / optimum or maximum amount of light is being absorbed (by the pigments) ; 5(c)(ii) any three from: 3 1 different wavelengths of light absorbed by different pigments ; 2 red light is absorbed the most ; 3 green light is, absorbed less / reflected ; 4 shorter the wavelength the greater the energy / red light has more energy (than blue light) ; ora 5 the more, light / energy, absorbed the more, light dependent reaction / photophosphorylation, occurs ; ora © UCLES 2021 Page 13 of 22

5(a) any two from: 2 1 cyclic involves (only) PS1 and non-cyclic involves PS1 and PS2 ; 2 cyclic produces only ATP and non-cyclic produces ATP and reduced NADP ; 3 cyclic does not involve photolysis of water and non-cyclic does involve photolysis of water ; A photolysis only occurs in non-cyclic 5(b)(i) as a, control / reference tube, for comparison ; R control variable 1 5(b)(ii) tube 2 changes to blue 5 1 (plant carries out) photosynthesis ; 2 uses up CO in the, Calvin cycle / light independent stage 2 or less CO causes pH to increase ; I oxygen 2 tube 3 changes to yellow 3 (snail carries out) respiration ; 4 produces CO in, the link reaction / Krebs cycle 2 or more CO causes pH to decrease ; A more CO acidifies solution I oxygen 2 2 tube 4 stays green 5 both photosynthesis and respiration or CO produced in respiration is used in photosynthesis 2 or oxygen produced in photosynthesis is used in respiration ; © UCLES 2021 Page 12 of 22 9700/43 Cambridge International AS & A Level – Mark Scheme May/June 2021 PUBLISHED Question Answer Marks 5b(iii) any three from: 3 1 no / less, photosynthesis, so, no / less, CO used ; 2 2 detail ; e.g. no light dependent stage / no non-cyclic photophosphorylation no / less, Calvin cycle / light independent stage / carbon (dioxide)fixation 3 respiration occurs producing CO ; 2 4 respiration rate slower, in aquatic plants / test-tube 6, than, pond snails / test-tube 7 ; 5 (so) slight decrease in pH ; © UCLES 2021 Page 13 of 22

2(a)(i) any four from: 4 differences 1 cotton (enzyme / rubisco activase) has a higher, optimum temperature / temperature at which activity is highest ; ora 2 maximum / highest / peak, activity higher in flax (enzyme / rubisco activase) (than in cotton) ; ora 3 cotton (enzyme / rubisco activase) can work at higher temperature (than flax) ; 4 (at stated temp) <30 °C flax (enzyme) has higher activity than cotton ; ora 5 (at stated temp) >30 °C cotton (enzyme) has higher activity than flax ; ora similarities 6 (activity of) both increases then decreases as temperature increases ; 7 (enzyme / rubisco activase) activity, same / 0.104 (au), at 30 °C ; 2(a)(ii) any three from: 3 1 cotton, is adapted to / lives in areas with, high(er) temperatures ; ora 2 ref. to different, genes / alleles (in cotton vs. flax) ; 3 ref. to different primary structure of rubisco activase (in cotton vs. flax) ; 4 ref. to different tertiary structure of rubisco activase (in cotton vs. flax) ; 5 AVP ; © UCLES 2021 Page 6 of 21 2(b) any three from: 3 1 less / no, CO fixation / carboxylation of RuBP ; 2 2 less / no, GP, made into / converted to, TP ; 3 less / no, regeneration of RuBP ; 4 less / no, glucose / hexose, made ; 2(c) any two from: 2 1 take, gene / (c)DNA, for rubisco activase ; 2 from, cotton and insert into, (false) flax / (named crop) plant / embryo ; 3 to maintain rubisco action at, high temperatures / >37.5 °C / up to 42.5 °C ; 4 AVP ; © UCLES 2021 Page 7 of 21

9(a) any seven from 7 1 (H+) carrier / pump (protein), in cell surface membrane (of guard cell) ; 2 hydrogen ions / protons / H ions / H+, leave / exit (cell) ; 3 using, energy / ATP ; 4 low H+ (in cell) / more negative charge (than outside) ; 5 K+ channel (proteins) open ; 6 K+, move into / enter, cell (by facilitated diffusion) ; 7 Cl – ions, move into / enter (cell) ; 8 water / solute, potential of cell decreases ; 9 water moves in (to cell) by osmosis ; 10 cell / vacuole, volume increases ; 11 (cells) are / become, turgid ; 12 thick inner cell wall (of guard cell) ; 13 AVP ; © UCLES 2021 Page 18 of 21 9(b) any eight from: 8 1 C4, plants / pathway ; 2 stop / decrease, photorespiration ; 3 mesophyll cells form (tightly packed) ring ; 4 around / surrounding, bundle sheath (cells) ; 5 (initial) CO carbon, fixation in mesophyll and Calvin cycle in bundle sheath ; 2 / 6 RuBP / rubisco, in bundle sheath (cells) ; 7 oxygen / air, cannot reach, RuBP / rubisco / bundle sheath ; 8 CO combines with, PEP / PEP carboxylase (in mesophyll) ; 2 9 to form, oxaloacetate / malate ; 10 (malate) releases carbon dioxide in bundle sheath (cells) ; 11 RuBP, carboxylated / reacts with carbon dioxide ; 12 PEP carboxylase has high optimum temperature / tolerates high temperatures ; © UCLES 2021 Page 19 of 21

2(a) any one from: 1 1 industrialisation ; 2 transportation ; 3 power stations ; 4 burning of fuels ; © UCLES 2021 Page 6 of 24 2(b) any three from: 3 1 genetically modified has a higher (dry) mass throughout the experiment ; ora 2 genetically modified has a (slightly) higher rate of / steeper, increase (in dry mass) ; ora 3 the largest difference in (dry) mass is after day 8 ; 4 paired data quote with units ; time / days dry mass / g dm–3 genetically modified unmodified difference between the two ± 0.02 ± 0.02 ± 0.04 2 0.22 0.13 0.09 4 0.48 0.34 0.14 6 0.62 0.48 0.14 8 0.88 0.74 0.14 10 1.24 0.96 0.28 12 1.54 1.31 0.23 14 1.86 1.52 0.34 rate of growth over 14 days genetically modified = 1.86 / 14 = 0.13 g dm–3 day–1 unmodified = 1.52 / 14 = 0.11 g dm–3 day–1 © UCLES 2021 Page 7 of 24 2(c) any three from: 3 1 (more rubisco so) greater rate of / more, carbon (dioxide) fixation ; AW 2 (so) greater rate of / more, GP produced ; 3 so greater rate of / more TP, produced (from GP) ; 4 (so) greater rate of / more, regeneration of RuBP ; 5 (so) greater rate of / more, Calvin cycle ; 6 AVP ; e.g. carbon fixation is a rate-limiting step / concentration of rubisco is a limiting factor 2(d) any three from: 3 1 glucose for respiration ; 2 starch for storage ; 3 cellulose to make cells walls ; 4 sucrose for, translocation / described ; 5 fatty acids and glycerol / lipid, to make membranes or fatty acids and glycerol / lipid / fats, for storage or fatty acids to make acetyl CoA (for Krebs cycle) ; 6 amino acids to make, proteins / enzymes ; 7 proteins for, growth / repair ; © UCLES 2021 Page 8 of 24 2(e) any one from: 1 1 idea of fast(er) growth rate / reproduction ; 2 quicker to set up / AW ; 3 cheaper to set up / AW ; 4 (as aquatic) not using (useful) land ; 5 can, culture / grow, algae in the lab ; Question Answer Marks

2(a)(i) any four from: 4 differences 1 cotton (enzyme / rubisco activase) has a higher, optimum temperature / temperature at which activity is highest ; ora 2 maximum / highest / peak, activity higher in flax (enzyme / rubisco activase) (than in cotton) ; ora 3 cotton (enzyme / rubisco activase) can work at higher temperature (than flax) ; 4 (at stated temp) <30 °C flax (enzyme) has higher activity than cotton ; ora 5 (at stated temp) >30 °C cotton (enzyme) has higher activity than flax ; ora similarities 6 (activity of) both increases then decreases as temperature increases ; 7 (enzyme / rubisco activase) activity, same / 0.104 (au), at 30 °C ; 2(a)(ii) any three from: 3 1 cotton, is adapted to / lives in areas with, high(er) temperatures ; ora 2 ref. to different, genes / alleles (in cotton vs. flax) ; 3 ref. to different primary structure of rubisco activase (in cotton vs. flax) ; 4 ref. to different tertiary structure of rubisco activase (in cotton vs. flax) ; 5 AVP ; © UCLES 2021 Page 6 of 21 2(b) any three from: 3 1 less / no, CO fixation / carboxylation of RuBP ; 2 2 less / no, GP, made into / converted to, TP ; 3 less / no, regeneration of RuBP ; 4 less / no, glucose / hexose, made ; 2(c) any two from: 2 1 take, gene / (c)DNA, for rubisco activase ; 2 from, cotton and insert into, (false) flax / (named crop) plant / embryo ; 3 to maintain rubisco action at, high temperatures / >37.5 °C / up to 42.5 °C ; 4 AVP ; © UCLES 2021 Page 7 of 21

9(a) any seven from 7 1 (H+) carrier / pump (protein), in cell surface membrane (of guard cell) ; 2 hydrogen ions / protons / H ions / H+, leave / exit (cell) ; 3 using, energy / ATP ; 4 low H+ (in cell) / more negative charge (than outside) ; 5 K+ channel (proteins) open ; 6 K+, move into / enter, cell (by facilitated diffusion) ; 7 Cl – ions, move into / enter (cell) ; 8 water / solute, potential of cell decreases ; 9 water moves in (to cell) by osmosis ; 10 cell / vacuole, volume increases ; 11 (cells) are / become, turgid ; 12 thick inner cell wall (of guard cell) ; 13 AVP ; © UCLES 2021 Page 18 of 21 9(b) any eight from: 8 1 C4, plants / pathway ; 2 stop / decrease, photorespiration ; 3 mesophyll cells form (tightly packed) ring ; 4 around / surrounding, bundle sheath (cells) ; 5 (initial) CO carbon, fixation in mesophyll and Calvin cycle in bundle sheath ; 2 / 6 RuBP / rubisco, in bundle sheath (cells) ; 7 oxygen / air, cannot reach, RuBP / rubisco / bundle sheath ; 8 CO combines with, PEP / PEP carboxylase (in mesophyll) ; 2 9 to form, oxaloacetate / malate ; 10 (malate) releases carbon dioxide in bundle sheath (cells) ; 11 RuBP, carboxylated / reacts with carbon dioxide ; 12 PEP carboxylase has high optimum temperature / tolerates high temperatures ; © UCLES 2021 Page 19 of 21

6(a)(i) 1 CO uptake below zero / CO released / CO uptake is negative / CO uptake is –1.6 μmol m–2 s–1 ; 3 2 2 2 2 plus any two from: 2 little photosynthesis occurring / AW ; R no photosynthesis 3 due to low light intensity ; 4 rate of respiration higher than rate of photosynthesis ; A idea that there is more respiration than photosynthesis 6(a)(ii) any three from: 3 1 as light intensity increases rate of CO uptake increases / AW ; 2 2 data quote to support mp1 ; e.g. carbon uptake is –0.2 μmol m–2 s–1 at 2000 lux and 6.5 μmol m–2 s–1 at 7000 lux 3 (because) rate of, photosynthesis / light-dependent reactions / light-independent reactions, increases ; 4 light intensity is limiting factor ; 6(a)(iii) light intensity is no longer limiting 1 or carbon dioxide concentration / temperature, now limiting ; 6(b)(i) hydrolytic / extracellular / protease / proteinase / peptidase / AW ; 1 6(b)(ii) amino acid(s) / proteins / nucleotides ; 2 glycerate-3-phosphate / GP or triose phosphate / TP ; © UCLES 2022 Page 16 of 22

2(a) any four from: 4 structure function 1 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, to absorb (more) light ; have large surface area / are many in number 4 stroma for light independent reaction / Calvin cycle ; 5 stroma has, (named) enzymes / RuBP / reduced NADP ; 6 stroma colourless OR so light reaches thylakoids OR stroma contains water 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 ; 9 envelope compartmentalisation ; 2(b) any three from: 3 1 light excites electrons in, P700 / PS1 (reaction centre chlorophyll) ; 2 electrons passed, along carriers / to ETC ; 3 H+ / protons, pumped into thylakoid, space / lumen ; 4 H+ / protons, diffuse (back to stroma) through ATP synth(et)ase ; 5 makes ATP ; 6 AVP ; © UCLES 2022 Page 8 of 19 2(c) any seven from: 7 description D1 identify wavelengths for chlorophyll (a) absorption ; D2 identify wavelengths for phycoerythrin absorption ; D3 identify wavelengths for phycocyanin absorption ; D4 chlorophyll (a), has peaks / absorbs mainly, in blue and red ; D5 phycoerythrin absorbs in blue and green and yellow ; D6 phycocyanin absorbs in (green) yellow and red ; explanation E7 red algae / deep water, get(s) green (and yellow) light ; E8 chlorophyll (a) absorbs, no / little, green (and yellow) light ; E9 phycoerythrin / phycocyanin / accessory pigments, absorbs wavelengths not absorbed by chlorophyll (a) ; E10 combined pigments absorb, greater range of / any / all, wavelengths ; E11 increases / more / high(er) rate of, light dependent stage / photosynthesis ; E12 (so) more / lots of, (named) organic compounds / growth ; Question Answer Marks

9(a) 2 letter feature B location of Calvin cycle ; D made of cellulose ; 9(b) any four from: 4 1 H+ pumped, out of guard cell / into cell wall of guard cell ; 2 inside of cell becomes (relatively) negatively charged ; 3 K+ enters cell by facilitated diffusion ; 4 water potential of cell decreases ; 5 water enters cell by osmosis ; 6 cell, expands / increases in volume / becomes turgid ; 7 stoma opens due to thick inner wall ; © UCLES 2022 Page 17 of 19

2(a)(i) any two from: 2 1 ref. to light energy / photons ; 2 for, light-dependent stage / photophosphorylation / photolysis / photoexcitation / photoactivation ; 3 to make, reduced NADP / ATP ; 4 to open stomata (for CO to enter) ; 2 2(a)(ii) correctly showing that TP reduces to a plateau below GP ; 2 correctly showing that RuBP increases to a plateau ; © UCLES 2022 Page 6 of 22 2(a)(iii) 1. decrease in / no, CO , diffusing / moving, to, 3 2 air spaces / palisade cells / mesophyll cells / chloroplasts / stroma ; any two from: 2 stress response / AW ; 3 ref. to abscisic acid / ABA ; 4 ref. to action of Ca2+ as a second messenger ; 5 stomata close ; 2(b)(i) 2820.5 7.5 2  100 or  100 ; A 20.4 or 20.6 20.5 20.5 A 37.3 or 35.9 answer to 1 decimal place 36.6 (%) ; apply ecf © UCLES 2022 Page 7 of 22 2(b)(ii) any four from: 4 no mention of increased or more – ecf and max 3 1 Sox4 plants have an extra copy of SBPase gene ; 2 (overall) increased, expression / transcription, of SBPase gene (so more SBPase) ; 3 increased (rate of) / more, regeneration / production, of RuBP ; 4 (so) increased / more, carbon fixation / Calvin cycles / light independent reaction / TP / GP ; 5 more, glucose / sucrose, for respiration / ATP production or more, starch / lipid, for storage or more cellulose for cell walls ; 6 more, amino acids / proteins, for growth ; 7 more, cell division / cell elongation / mitosis ; 8 AVP ; e.g.(new) SBPase / SBPase gene, more efficient 2(b)(iii) nitrogen needed to produce: 2 nucleotides for, transcription (of SBPase gene) / expression (of SBPase gene) / mRNA production ; amino acids for, protein synthesis / SBPase production / enzyme production ; © UCLES 2022 Page 8 of 22

2(a)(i) any four from: 4 similarities 1 photoactivation of chlorophyll / AW, occurs in both ; A excite electrons (for AW) 2 ETC involved in both ; 3 ATP produced in both ; differences cyclic non-cyclic 4 only PSI PSI and PSII both involved ; 5 no, reduced NADP / oxygen, produced reduced NADP / oxygen, produced ; 6 no photolysis photolysis ; or or no oxygen-evolving oxygen-evolving complex involved complex involved 7 electrons emitted from PSI electrons emitted from PSII are replaced by water ; returned to PSI or or water is source of electrons PS1 is source of electrons © UCLES 2022 Page 7 of 23 2(a)(ii) any two from: 2 1 no ATP and reduced NADP made ; 2 no, GP / TP, made or no, Calvin cycle / light-independent reaction ; 3 no regeneration of RuBP ; 2(b)(i) any four from: 4 1 as the CO concentration increases, the rate of fixation of CO increases ; 2 2 2 (as) CO concentration is the limiting factor ; 2 3 as the CO concentration increases, the rate of fixation of CO , remains the same / plateaus ; 2 2 4 (as) CO concentration is no longer the limiting factor 2 or temperature / light intensity / RuBP regeneration, is the limiting factor ; 5 paired data quote with units to support, mp1 / mp3 ; CO concentration / mg m–3 CO fixation rate / µmol CO m–2 s–1 2 2 2 mp1 50 ±10 1 ±0.25 1200–1280 42 A 41.75 mp3 from 1200–1910 42 A 41.75 © UCLES 2022 Page 8 of 23 2(b)(ii) any three from: 3 assume Sox4 – accept ora for wild 1 the rate of fixation of CO is higher in Sox4 compared to wild type 2 or Sox4 reaches a higher (maximum) rate of CO fixation ; 2 2 (wild type) 42 vs (Sox4) 47 mol CO m–2s–1 ; 2 3 (Sox4 has) more SBPase or there is a faster (rate of) regeneration of RuBP or (new) SBPase more effective ; 4 more RuBP to react with, CO / rubisco ; 2 © UCLES 2022 Page 9 of 23

2(a) chlorophyll a / chlorophyll b / () carotene ; 1 2(b) any two from: 2 1 action (spectrum) shows rate of photosynthesis for light, wavelengths / colours ; 2 absorption (spectrum) shows how much each, wavelength / colour, is absorbed ; 3 higher absorption gives higher photosynthesis ; 2(c) any three from: 3 1 ref. (named) enzymes ; 2 high(er) temperature increases rate ; 3 (temperature affects) photophosphorylation / light-dependent / Calvin cycle / light-independent / ESC formation ; ora 4 enzymes denature at, too high a temperature / very high temperature / above optimum temperature ; 5 AVP ; 2(d) any three from: 3 1 RuBP joins with CO to make, 6C intermediate / GP ; 2 2 GP to TP ; 3 (GP → TP) uses ATP and reduced NADP ; 4 TP → glucose / hexose → starch ; 5 condensation / polymerisation / glycosidic bonds ; © UCLES 2022 Page 7 of 19

3(a)(i) D ; 2 B ; 3(a)(ii) any four from: 4 1 thylakoid stacks or discs / many thylakoids, for, increased or large, surface area ; 2 increased or large, surface area maximises the absorption of light (energy) / AW ; Ignore trap (light energy) mp 3–5 thylakoid membranes / grana contain 3 photosynthetic / named / primary / accessory, pigments to absorb light (energy) ; 4 electron carriers / ETC, to, transfer / release, energy (from excited electrons) ; 5 photosystems / antenna complex and reaction centre, are light harvesting structures ; 6 thylakoid space or lumen to, form proton gradient / have high concentration of protons ; 7 thylakoid membrane is (relatively) impermeable, to maintain the proton gradient (for chemiosmosis) ; 8 ATP synthase to make ATP ; 9 contains oxygen-evolving complex / OEC, for the photolysis of water ; © UCLES 2022 Page 8 of 19 3(b)(i) any three from: 3 1 the pH is higher in the light than in the dark ora or the pH increases (from dark) to light or the pH decreases (from light) to dark ; 2 the pH, increases sharply / AW, when changed to light ; 3 the pH, levels off / AW, in light ; 4 the pH decreases, gradually / less steeply, when returned to the dark or decrease in pH does not return to original (dark) pH ; 5 ref. to fluctuations anywhere / described ; 6 comparative figures to support ; (mp1) dark(1) ~ pH 7.31–7.6 vs light ~ 7.52–7.61 vs dark (2) ~ 7.51–7.38 (mp2) from pH 7.36–7.56 in 36 s (1½ squares and each square 24 s) (mp4) from pH 7.56–7.4 in 288 s (12 squares) 3(b)(ii) any three from: 3 1 the stroma has higher pH when H+ ions, move, out (of stroma) / into thylakoid, space / lumen ; 2 (leads to) increased H+ concentration in the thylakoid, space / lumen ; 3 (then) H+ diffuse back (into stroma) through ATP synthase ; 4 AVP ; e.g. idea not to support theory © UCLES 2022 Page 9 of 19

2(a) chlorophyll a / chlorophyll b / () carotene ; 1 2(b) any two from: 2 1 action (spectrum) shows rate of photosynthesis for light, wavelengths / colours ; 2 absorption (spectrum) shows how much each, wavelength / colour, is absorbed ; 3 higher absorption gives higher photosynthesis ; 2(c) any three from: 3 1 ref. (named) enzymes ; 2 high(er) temperature increases rate ; 3 (temperature affects) photophosphorylation / light-dependent / Calvin cycle / light-independent / ESC formation ; ora 4 enzymes denature at, too high a temperature / very high temperature / above optimum temperature ; 5 AVP ; 2(d) any three from: 3 1 RuBP joins with CO to make, 6C intermediate / GP ; 2 2 GP to TP ; 3 (GP → TP) uses ATP and reduced NADP ; 4 TP → glucose / hexose → starch ; 5 condensation / polymerisation / glycosidic bonds ; © UCLES 2022 Page 7 of 19

8(a) any seven from: 7 1 photosynthetic / named / primary / accessory, pigments to absorb light (energy) ; 2 ref. to, photosystems / antenna complex and reaction centre / light harvesting structures ; 3 photoactivation / electrons excited / emission of electrons ; 4 electrons move along electron transport chain ; 5 (cyclic / non-cyclic) photophosphorylation / light-dependent stage ; 6 site of photolysis / location of oxygen-evolving complex ; 7 thylakoids stacked to form grana ; 8 gives large surface area ; 9 thylakoid space or lumen to, form proton gradient / have high concentration of protons ; 10 thylakoid membrane is (relatively) impermeable, to maintain the proton gradient ; 11 ATP synthase to make ATP; 12 chemiosmosis ; © UCLES 2023 Page 16 of 20 8(b) any four from: 4 describe 1 A activity increases and B activity remains, low / constant ; 2 comparative data quote ; e.g. 3.0–3.2 at 0.5 mins and 11.4–11.6 at 6 mins for A 0.4 throughout for B max three: explanation: 3 RA / rubisco activase, activates rubisco ; 4 by changing the active site of rubisco ; 5 by enabling rubisco to bind more readily with, RuBP / substrate or more enzyme–substrate complexes ; 6 enables products to leave active site more quickly ; 7 AVP ; e.g. cofactor action qualified Question Answer Marks

1(a) 4 description letter accumulates (builds up) a high concentration of protons B ; makes triose phosphate A ; makes some chloroplast proteins D ; pumps protons C ; 1(b)(i) any four from: 4 1 spot / extract, placed on, pencil line / base line / line of origin ; 2 repeat / concentrate, spot / extract ; 3 end / base, of paper, suspended / placed, in (named) solvent ; 4 mark the solvent front after, some time / paper removed / solvent moves ; 5 R value = distance moved by, spot / pigment / component / solute ÷ distance moved by solvent (front) ; f 6 compare (R) with known R values to identify, constituents / pigments ; f f 7 detail of method ; 1(b)(ii) any three from: 3 1 (pigments / they / to) absorb / capture / harvest, light (energy) ; 2 increase (range of) / more / different, wavelengths / colours of light, can be absorbed ; 3 increase, efficiency / rate, of, photosynthesis / light dependent reaction OR increase / broader, action spectrum ; 4 ref. two of: chlorophyll a / chlorophyll b / carotene / xanthophyll ; © UCLES 2023 Page 8 of 17

8(a)(i) any two from: 3 1 higher rate of activity (of rubisco) in GM rice (throughout) ; 2 (low CO concentrations) rate of activity for both increases ; 2 3 comparative figures – GM and non-GM at one CO concentration ; 2 atmospheric CO rate of activity of rubisco / arbitrary units 2 concentration / mg dm–3 non-GM rice GM-rice 5 0.05 0.05 0 0.7 0.80 100 1.8 2.70 200 2.4 3.95 280 2.6 4.15 300 2.6 4.15 400 2.6 4.30 500 2.6 4.45 600 2.6 4.55 © UCLES 2023 Page 22 of 25 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 1 8(b)(i) carbon (dioxide) fixation ; A carboxylation 1 8(b)(ii) reduction / hydrogenation ; 1 8(b)(iii) 6 / 5 ; 1 8(b)(iv) any two from: list rule 2 1 hexose / named ; e.g. glucose / fructose 2 disaccharide / named ; e.g. sucrose / maltose 3 starch / cellulose ; 4 amino acids ; 5 glycerol / fatty acids ; © UCLES 2023 Page 23 of 25

8(a) 4 letter high concentration of protons M ; location of photosynthetic pigments L or N ; site of light-independent stage K ; site of light-dependent stage L or N ; ignore M in the last row 8(b) any four from: 4 1 any one named ; e.g. chlorophyll b / carotene / xanthophyll / carotenoids ; 2 act as accessory pigments / part of antenna complex / part of light harvesting system ; 3 absorb, light / photons ; 4 pass energy on to, chlorophyll a / primary pigment / reaction centre ; 5 absorb different wavelengths of light / wavelengths not absorbed by chlorophyll a ; © UCLES 2023 Page 20 of 24 8(c) 1 absorption higher for (whole) chloroplasts (throughout) ; 4 2 comparative data quote or greatest difference at 525 / 530 nm ; absorbance / au wavelength 0.05 / nm whole pigment 500 9.2 6.4 510 8.4 3.8 520 7.4 2.3 525 7.0 1.95 530 6.6 1.85 540 6.2 2.05 550 5.8 2.35 560 5.8 2.7 600 6.65 4.7 650 8.85 8.1 670 9.6 9.2 3 (because) pigments arranged for better absorption in chloroplasts / thylakoid membranes are stacked / AW ; 4 (because) chloroplasts contain more pigments ; © UCLES 2023 Page 21 of 24

1(a)(i) thylakoid(s) ; 1 1(a)(ii) any four from: 4 up to three descriptions (D) and one / two linked functions (F) D1 stacked / many (A / thylakoids) / large surface area ; F2 to increase light absorption ; D3 (thylakoid) membrane has, (named), pigments / photosystems / electron carriers / enzymes ; F4 (thylakoid membrane role is) light-dependent reaction / photophosphorylation / creates proton gradient / pump protons / chemiosmosis / makes ATP ; D5 (thylakoid) lumen / space ; F6 accumulates H+ / high H+ concentration ; D7 appear green (under microscope) ; F8 as / so, chlorophyll absorbs red and blue light ; 1(b)(i) Calvin (cycle) ; 1 1(b)(ii) any two from: 2 1 no start and end, point / molecules ; 2 all, molecules / intermediates, present all the time ; 3 ribulose bisphosphate / RuBP / 5C molecule, is regenerated ; 4 numerical detail ; 1(c)(i) B: oxygen ; 2 D: sugar / hexose / glucose / triose phosphate / carbohydrate / starch ; 1(c)(ii) 1 (oxygen linked to) aerobic respiration / oxidative phosphorylation ; 3 2 (glucose stated as) source / store, of (chemical) energy / ATP / food ; 3 ref. to energy flow through, food chains / food web / ecosystem ; © UCLES 2023 Page 7 of 16

8(a) any four from: 4 1 both photosystem I and photosystem II involved ; A both photosystems 2 photoactivation of chlorophyll occurs ; 3 photolysis of water occurs / description ; 4 oxygen production / oxygen-evolving complex involved ; 5 electrons emitted by photosystem I used to reduce NADP or NADP is the final electron acceptor ; 6 photosystem I receives electrons from photosystem II or photosystem II receives electrons from photolysis (of water) ; 7 ETC / electron transport chain, sets up proton gradient or chemiosmosis / ATP produced ; 8(b) GP used to make, amino acids / fatty acids / lipids ; 2 TP used to make, hexose / starch / cellulose / amino acids / glycerol / lipids ; 8(c)(i) 3.10−1.55 3.10−1.50 2 or ; 15 15 0.10 / 0.11 ; 8(c)(ii) any three from: 3 1 temperature now not limiting or carbon dioxide concentration now limiting ; 2 closure of stomata ; 3 lack of water / AW ; 4 denaturation of enzymes or active site no longer complementary to substrate / no ESCs form ; 5 AVP ; e.g. ref. to optimum temperature / photorespiration occurs © UCLES 2023 Page 15 of 18 8(c)(iii) similar shape but below high intensity curve ; 1 Question Answer Marks

1(a)(i) thylakoid(s) ; 1 1(a)(ii) any four from: 4 up to three descriptions (D) and one / two linked functions (F) D1 stacked / many (A / thylakoids) / large surface area ; F2 to increase light absorption ; D3 (thylakoid) membrane has, (named), pigments / photosystems / electron carriers / enzymes ; F4 (thylakoid membrane role is) light-dependent reaction / photophosphorylation / creates proton gradient / pump protons / chemiosmosis / makes ATP ; D5 (thylakoid) lumen / space ; F6 accumulates H+ / high H+ concentration ; D7 appear green (under microscope) ; F8 as / so, chlorophyll absorbs red and blue light ; 1(b)(i) Calvin (cycle) ; 1 1(b)(ii) any two from: 2 1 no start and end, point / molecules ; 2 all, molecules / intermediates, present all the time ; 3 ribulose bisphosphate / RuBP / 5C molecule, is regenerated ; 4 numerical detail ; 1(c)(i) B: oxygen ; 2 D: sugar / hexose / glucose / triose phosphate / carbohydrate / starch ; 1(c)(ii) 1 (oxygen linked to) aerobic respiration / oxidative phosphorylation ; 3 2 (glucose stated as) source / store, of (chemical) energy / ATP / food ; 3 ref. to energy flow through, food chains / food web / ecosystem ; © UCLES 2023 Page 7 of 16

7(a)(i) light not absorbed / stop photosynthesis / stop photoactivation / 1 stop light dependent stage ; © Cambridge University Press & Assessment 2024 Page 13 of 21 7(a)(ii) any three from: 3 1 all decrease in absorbance (with time) ; 2 (all decrease) at constant rate ; 3 green, highest absorbance (throughout) / absorbance stays fairly constant / smallest decrease in absorbance ; ora red 4 smallest rate of decrease in green ; ora red 5 data quote – 2 colours compared to support mp1 or mp3 ; 4 mins green 1.44 blue 0.90 red 0.70 7(a)(iii) any three from: 3 with red light ora green light 1 more, light / energy, absorbed (by chlorophyll) ; 2 (so) more, photoactivation / electrons emitted ; 3 more / faster rate of, electrons transferred to DCPIP ; 4 more / faster, decolourisation of DCPIP ; © Cambridge University Press & Assessment 2024 Page 14 of 21 7(b) 3 factor stage ✓or  Calvin cycle ✓ carbon dioxide ; concentration photophosphorylation  Calvin cycle  light intensity ; photophosphorylation ✓ Calvin cycle ✓ temperature ; photophosphorylation ✓ Question Answer Marks

5(a)(i) A = stroma ; 2 B = thylakoid, lumen / space ; 5(a)(ii) 1 cyclic photophosphorylation ; 2 2 ATP synth(et)ase ; 5(a)(iii) 1 D = reduced NADP ; 3 2 reduces / gives hydrogen to, glycerate (3) phosphate / GP ; 3 forming, triose phosphate / TP ; 5(b)(i) any three from: 3 D1 rate of energy transfer, higher / highest, for tropical or rate of energy transfer, lower / lowest, for snow forest ; D2 paired data quote with units (at least once) ; S3 tropical forest has, high(er/est) temperature / hot(ter) ; S4 tropical forest has high(er/est) light, intensity / duration ; S5 temperature / light intensity, is a limiting factor (on photosynthesis) ; © Cambridge University Press & Assessment 2024 Page 9 of 15 5(b)(ii) any three from: 3 1 more, transpiration / water loss (from leaves) ; 2 stomata shut reducing, carbon dioxide (entry) / gas exchange ; 3 (so) carbon dioxide (concentration) is a limiting factor ; 4 (grassland / desert) fewer plants / less plant cover / smaller plants ; 5 (so smaller surface area) less light absorbed ; 6 AVP ; Question Answer Marks

7(a)(i) 1 rate of oxygen produced / rate of photosynthesis, is low / stays constant 3 or small decrease in, rate of oxygen produced / rate of photosynthesis ; 2 light intensity was the limiting factor / AW ; 3 (so) less / little, light energy absorbed / photolysis (of water) / photoactivation (of chlorophyll)/ light-dependent reactions / photophosphorylation ; R no light energy absorbed © Cambridge University Press & Assessment 2024 Page 14 of 20 7(a)(ii) any three from: 3 1 rate of oxygen produced / rate of photosynthesis, decreased ; 2 two paired data quotes with units ; temperature / °C rate of oxygen production / mm3 h–1 30 4 / 4.00 40 2.55 50 0.65 (A 0.62-0.65) 3 because, enzyme / ATP synthase / NADP reductase / oxygen evolving complex, denatured ; A rubisco 4 change in active site / fewer ESCs ; 7(b) any three from: 3 1 light absorbed by, photosystem II / P680 or photoactivation / photoionisation (of chlorophyll) ; 2 photolysis (of water) ; 3 water-splitting enzyme / oxygen evolving complex ; 4 water splits into protons, electrons and oxygen ; A equation © Cambridge University Press & Assessment 2024 Page 15 of 20

7(a)(i) 1 light intensity total CO uptake after rate of photosynthesis 2 / lux 20 seconds / μmols-1 / μmol 0 0 0.0 3 20 10 6 44 22 ; 9 72 36 12 80 40 7(a)(ii) five points plotted correctly ; 3 best fit curve drawn for plots ; curve levels off from 12 lux to 18 lux or curve continues up at smaller gradient ; 7(a)(iii) curve levels off from 12 lux to 18 lux 2 1 because light intensity no longer limiting ; 2 temperature / carbon dioxide concentration, now limiting ; © Cambridge University Press & Assessment 2024 Page 15 of 20 7(b) any four from: 4 1 electrons, excited / emitted / described ; 2 electrons travel along ETC and energy released ; 3 (use energy released) to pump H+ into thylakoid, space/ lumen ; 4 increases concentration of H+ / protons (in thylakoid space / lumen) / creates proton gradient ; 5 H+ / protons, diffuse through ATP synthase ; 6 (from thylakoid space) to stroma ; 7 chemiosmosis ; © Cambridge University Press & Assessment 2024 Page 16 of 20

4(a) any three from: 3 in Venus fly traps 1 touch two (sensory hairs) ; 2 protons, leave hinge cells / enter hinge cell walls ; 3 Ca2+ ions move into (hinge) cells ; 4 water moves into (hinge) cells ; 5 (hinge) cells, become turgid / swell / increase in volume / expand ; 4(b) any two from: 2 1 less / decreased, surface area (of leaf exposed) ; 2 less light absorbed by, chloroplasts / thylakoid membranes / grana / pigments / chlorophyll / light harvesting complexes / photosystems ; 3 fewer stomata, exposed / available (to air) ; 4 less carbon dioxide, enters / absorbed ; 4(c) any six from: 6 similarities 1 photoactivation of chlorophyll ; 2 (energetic) electrons move, along / down, ETC ; 3 chemiosmosis ; 4 ATP produced ; differences 5 PSI and PSII in non-cyclic and only PSI in cyclic ; 6 photolysis / oxygen produced, in non-cyclic only ; ORA 7 reduced NADP in non-cyclic only ; ORA 8 electrons return to, same photosystem / PSI, in cyclic ; © Cambridge University Press & Assessment 2024 Page 9 of 15

7(a) 1 calculate R value(s) ; 3 f 2 (R = ) distance moved by pigment (from baseline) f distance moved by solvent (from baseline) ; 3 compare with, known / standard / table, values ; 7(b) any three from: 3 1 absorb light wavelengths not absorbed by, reaction centre / primary pigment / chlorophyll a ; A harvest 2 so extend the range of wavelengths absorbed ; 3 pass energy to, reaction centre / primary pigment / chlorophyll a ; 4 ref. to accessory pigments ; © Cambridge University Press & Assessment 2024 Page 13 of 19 7(c) any seven from: 7 1 carbon dioxide, reacts / combines, with, ribulose bisphosphate / RuBP ; 2 (catalysed by) rubisco ; 3 ref. to carbon (dioxide) fixation ; 4 unstable 6C compound ; 5 forms 2 (molecules of) glycerate 3-phosphate / GP ; 6 glycerate 3-phosphate / GP, reduced to, triose phosphate / TP ; 7 by reduced NADP and ATP ; 8 triose phosphate / TP, used to regenerate RuBP ; 9 glycerate 3-phosphate / GP, forms amino acids ; 10 (some) TP forms, (named) hexoses / sucrose / maltose / starch / cellulose / glycerol / lipids / amino acids ; 11 ref. to Calvin cycle ; © Cambridge University Press & Assessment 2024 Page 14 of 19

4(a) any three from: 3 in Venus fly traps 1 touch two (sensory hairs) ; 2 protons, leave hinge cells / enter hinge cell walls ; 3 Ca2+ ions move into (hinge) cells ; 4 water moves into (hinge) cells ; 5 (hinge) cells, become turgid / swell / increase in volume / expand ; 4(b) any two from: 2 1 less / decreased, surface area (of leaf exposed) ; 2 less light absorbed by, chloroplasts / thylakoid membranes / grana / pigments / chlorophyll / light harvesting complexes / photosystems ; 3 fewer stomata, exposed / available (to air) ; 4 less carbon dioxide, enters / absorbed ; 4(c) any six from: 6 similarities 1 photoactivation of chlorophyll ; 2 (energetic) electrons move, along / down, ETC ; 3 chemiosmosis ; 4 ATP produced ; differences 5 PSI and PSII in non-cyclic and only PSI in cyclic ; 6 photolysis / oxygen produced, in non-cyclic only ; ORA 7 reduced NADP in non-cyclic only ; ORA 8 electrons return to, same photosystem / PSI, in cyclic ; © Cambridge University Press & Assessment 2024 Page 9 of 15

9(a) any two from: 2 1 accessory pigment ; 2 absorbs light wavelengths not absorbed by, reaction centre / primary pigment / chlorophyll a ; 3 so extends the range of wavelengths absorbed ; 4 pass energy to, reaction centre / primary pigment / chlorophyll a ; 5 idea that improves efficiency of light-dependent stage ; 9(b)(i) 1 rate of photosynthesis / rate of oxygen production, increases then levels off in both (plants) ; 3 2 rate of mutant plants higher than rate of normal plants ; 3 comparative data quote ; 9(b)(ii) any four from: 4 1 absorbs more light ; 2 so faster rate of, photosynthesis / light-dependent stage ; 3 more ATP and reduced NADP produced ; 4 more turns of Calvin cycle / AW ; 5 more, triose phosophate / TP, produced ; 6 more, hexose/ AW, for respiration ; 7 more energy for growth ; 8 more synthesis of, amino acids / proteins / lipids / cellulose / starch ; © Cambridge University Press & Assessment 2025 Page 18 of 19

4(a) any three from: 3 (both processes) 1 use / require, carbon dioxide / CO ; 2 2 use / require, water / H O ; 2 3 use / require, (sun) light energy / source of energy is light ; 4 make an organic, molecule / product ; 5 produce / release, oxygen / O ; 2 6 involve transduction of energy (from one form to another) ; 7 involve electron flow ; 4(b) A starch, grain / granule ; 2 B thylakoid (membrane) / lamella / granum ; 4(c)(i) ATP and reduced NADP (and oxygen) ; 1 4(c)(ii) any four from: 4 1 electron carriers / electron transport chain / to carry electrons ; 2 to release energy to, move / pump, protons (into, thylakoid space / lumen) or to release energy to generate proton gradient ; 3 oxygen-evolving, complex / enzyme ; 4 (to catalyse) splitting / photolysis, of water ; 5 LHC / antenna complex / photosystem, proteins hold pigments ; 6 ATP synth(et)ase to make ATP ; 4(d) triose phosphate ; 1 © Cambridge University Press & Assessment 2025 Page 11 of 17 4(e) any two plus one opposing arguments based on correct ref. to: 3 1 percentage / amount, of sunlight, absorbed / used ; 2 absorption / action, spectrum or wavelengths / colours of light, used ; 3 respiration of organism ; 4, 5 stage/transition, where, energy lost ; ; 6, 7 (named) limiting factor(s) ; ; 8 energy storage capability or night / dark, process ; 9 quality / nutrition in / palatability, of food product ; 10 proportion edible ; 11,12 additional energy inputs ; ; 13, 14 additional resources needed ; ; 15 labour / maintenance, needed ; 16 amount of space needed ; 17 plant, hormones / coordination ; 18 evolutionary adaptation ; © Cambridge University Press & Assessment 2025 Page 12 of 17

8(a) any four from: 4 1 eukaryotic / have nucleus ; 2 no, chlorophyll / chloroplasts ; 3 heterotrophic / saprophytic / saprotrophic / parasitic / described ; 4 cell wall made of, chitin / mannoproteins / glucans ; 5 reproduce by spores ; 6 hyphae / mycelium ; 7 cells may be multinucleate ; 8 either unicellular or multicellular ; 8(b) fungus receives, (named) organic compounds / nutrients / food / oxygen ; 2 alga receives, support / stability / protection / water / minerals / carbon dioxide ; © Cambridge University Press & Assessment 2025 Page 22 of 25 8(c)(i) (photosystem) II / 2 / 680 ; 1 8(c)(ii) A to B (occurs in very low light conditions) 4 respiration (rate) greater than photosynthesis (rate) ; (so) oxygen, consumed / not released ; after C light intensity not limiting ; carbon dioxide concentration / temperature, is limiting ; Question Answer Marks

7(a)(i) DNA ; 2 ribosome ; 7(a)(ii) thylakoid space ; 1 7(b) xanthophyll ; 3 3.4 ; 0.92 ; 7(c) any four from: 4 1 absorbs light between 400 and 500 nm / peak at 450 nm ; 2 accessory pigment ; 3 absorbs light wavelengths not absorbed by, reaction centre / primary pigment / chlorophyll a ; A harvest 4 so extends the range of wavelengths absorbed ; 5 pass energy to, reaction centre / primary pigment / chlorophyll a ; 6 idea improves efficiency of light-dependent stage ; © Cambridge University Press & Assessment 2025 Page 16 of 20

9(a) any seven from: 7 1 light absorbed by, chlorophyll / pigments (in PI and PII) or photoactivation of chlorophyll (in PI and PII) ; 2 electrons, emitted (to higher energy levels) / excited, in both photosystems ; 3 electrons pass along, electron transport chain / ETC / electron carriers ; 4 detail ; e.g. electrons releasing energy to pump H+ into thylakoid, space / lumen ref. to proton gradient set up protons diffusing through ATP synthase 5 ATP synthesised from ADP and P / ref. to chemiosmosis ; i 6 (PII contains) oxygen-evolving complex ; A water-splitting enzyme 7 ref. to photolysis (of water) ; 8 oxygen and hydrogen ions and electrons produced ; A H O 2e- + 2H+ + ½O 2 2 9 electrons emitted from PI replaced by electrons from PII or electrons emitted from PII replaced by electrons from photolysis (of water) ; 10 electrons (from PI) combine with H+ to form reduced NADP or electrons (from PI) combine with NADP to form reduced NADP or electrons (from PI) combine with H+ to form hydrogen that reduces NADP ; R H+ reduce NADP © Cambridge University Press & Assessment 2025 Page 25 of 27 9(b) 1 increase in light intensity increases rate of photosynthesis until it levels off (at higher light intensities) ; 3 2 (increase means) more, light dependent reaction / cyclic photophosphorylation / non-cyclic photophosphorylation / photoactivation ; 3 (as rate levels off) carbon dioxide concentration / temperature, becomes limiting factor or light intensity is no longer a limiting factor ; Question Answer Marks

3(a)(i) 0.95 (no units) ; ; 2 3(a)(ii) any two from: 2 1 B, run for less time / stopped early ; 2 chlorophyll, converted / changed, to phaeophytin ; 3 AVP ; 3(a)(iii) any one from: 1 1 different solvents ; 2 different, TLC plate / chromatogram / stationary phase (material) ; 3 different temperatures ; © Cambridge University Press & Assessment 2025 Page 10 of 18 3(b) any four from: 4 similarities 1 both absorb, blue / between 400 and 475 nm ; 2 both absorb, little / no, light between 525 and, 600 / 630, nm or both absorb, little / no, green / yellow, light ; 3 AVP ; max three differences 4 chlorophyll a absorbs, at more / a larger range of, wavelengths ; 5 chlorophyll a absorbs, more / better, between 400 and 445 nm ; 6 carotenoids absorb, more / better, between 445 and 525 nm ; 7 chlorophyll a absorbs between, 600 / 640, and, 680 / 690 nm, and carotenoids do not ; 8 chlorophyll a (blue absorption) peak / highest, at 425 / 430 nm and carotenoids (blue absorption) peak / highest, at 460 / 465 nm ; 9 chlorophyll a has blue peak and red peak but carotenoids have two blue peaks and no red peak or chlorophyll a has two peaks but carotenoids have three peaks ; 3(c) any four from: 4 1 gibberellin, moves to / acts on / stimulates, aleurone layer ; 2 binds to, (gibberellin) receptor / GID(1) ; 3 breaks down DELLA (protein) ; 4 releases, PIF / transcription factor ; 5 switches on gene for, amylase / maltase / protease ; 6 amylase, breaks down / hydrolyses, starch to maltose ; 7 sugars / glucose, for, respiration / growth, of embryo ; © Cambridge University Press & Assessment 2025 Page 11 of 18

9(a)(i) absorption spectrum 2 absorption of different wavelengths (of light) by (named) pigment(s) ; action spectrum rate of photosynthesis at different wavelengths (of light) ; 9(a)(ii) any three from : 3 1 chlorophyll b / carotenoids / accessory pigments (are present) ; 2 (these other pigments) absorb light (energy), between 450 and 550 nm / of wavelengths that chlorophyll a does not absorb ; 3 energy passed on to, reaction centre / chlorophyll a / primary pigment ; 4 for, light-dependent reactions / photophosphorylation / photolysis (of water) / photoactivation ; © Cambridge University Press & Assessment 2025 Page 20 of 23 9(b)(i) any four from : 4 1 increase then decrease ; 2 optimum temperature at 29 C ; 3 data quote – two temperatures and two rates with units ; temperature / C rate of photosynthesis / mg g-1 h-1 ±0.5 ±0.05 2.5 0.75 5 1.1 10 1.8 20 2.95 29 3.5 30 3.45 40 2.65 45 1.5 48 0.5 increase / before 29 C 4 more kinetic energy for, enzyme (activity) / AW ; 5 temperature is the limiting factor ; decrease / after 29 C 6 denaturation of, rubisco / enzymes / oxygen-evolving complex ; 7 AVP ; e.g. photorespiration limiting the rate at above 25 C © Cambridge University Press & Assessment 2025 Page 21 of 23 9(b)(ii) 3.525 to 3.675 ; 2 mg g–1 h–1 ; Question Answer Marks

3(a)(i) 0.95 (no units) ; ; 2 3(a)(ii) any two from: 2 1 B, run for less time / stopped early ; 2 chlorophyll, converted / changed, to phaeophytin ; 3 AVP ; 3(a)(iii) any one from: 1 1 different solvents ; 2 different, TLC plate / chromatogram / stationary phase (material) ; 3 different temperatures ; © Cambridge University Press & Assessment 2025 Page 10 of 18 3(b) any four from: 4 similarities 1 both absorb, blue / between 400 and 475 nm ; 2 both absorb, little / no, light between 525 and, 600 / 630, nm or both absorb, little / no, green / yellow, light ; 3 AVP ; max three differences 4 chlorophyll a absorbs, at more / a larger range of, wavelengths ; 5 chlorophyll a absorbs, more / better, between 400 and 445 nm ; 6 carotenoids absorb, more / better, between 445 and 525 nm ; 7 chlorophyll a absorbs between, 600 / 640, and, 680 / 690 nm, and carotenoids do not ; 8 chlorophyll a (blue absorption) peak / highest, at 425 / 430 nm and carotenoids (blue absorption) peak / highest, at 460 / 465 nm ; 9 chlorophyll a has blue peak and red peak but carotenoids have two blue peaks and no red peak or chlorophyll a has two peaks but carotenoids have three peaks ; 3(c) any four from: 4 1 gibberellin, moves to / acts on / stimulates, aleurone layer ; 2 binds to, (gibberellin) receptor / GID(1) ; 3 breaks down DELLA (protein) ; 4 releases, PIF / transcription factor ; 5 switches on gene for, amylase / maltase / protease ; 6 amylase, breaks down / hydrolyses, starch to maltose ; 7 sugars / glucose, for, respiration / growth, of embryo ; © Cambridge University Press & Assessment 2025 Page 11 of 18

10(a) any three from: 3 cyclic non-cyclic 1 photosystem I (only) vs photosystems I and II ; 2 electrons return to, same vs electrons do not return to ; photosystem / PSI / P700 same photosystem 3 ATP made vs ATP and reduced NADP ; made 4 no photolysis vs photolysis ; 5 no oxygen produced vs oxygen produced ; 10(b) 1 carbon dioxide ; 4 2 Rubisco ; 3 NADPH ; 4 glucose / hexose / starch / cellulose / glycerol / fatty acids / lipids / amino acids / proteins ; © Cambridge University Press & Assessment 2025 Page 17 of 17

10(a)(i) 2 crop number of number of stomatal stomata epidermal index / % cells cotton 6 32 ; 15.8 groundnut 9 36 20.0 mung bean 5 12 29.4 sorghum 8 20 28.6 tomato 7 25 21.9 ; 10(a)(ii) any two from: 2 1 allows sufficient, carbon dioxide uptake / gaseous exchange ; 2 reduces, transpiration / water loss ; 3 stomata on lower surface less exposed to, high light intensity / wind ; ora 4 allows more space for photosynthesis ; © Cambridge University Press & Assessment 2026 Page 24 of 25 10(b) ignore references to respiration 4 any four from: carbon dioxide concentration is decreasing 1 07:00 to 09:00, light intensity / temperature, is limiting factor ; 2 as, light intensity / temperature, is increasing rate of photosynthesis is increasing ; carbon dioxide concentration is, constant / low 3 09:00 to 17:30 carbon dioxide concentration is limiting factor ; 4 as rate of photosynthesis is high ; carbon dioxide concentration is increasing 5 17:30 to 22:00, light intensity / temperature, is limiting factor ; 6 as, light intensity / temperature, is decreasing the rate of photosynthesis is decreasing ; carbon dioxide concentration is, constant / high 7 22:00–06:00 / 07:00, light intensity is limiting factor ; 8 as, rate of photosynthesis is low / no photosynthesis ; 10(c) 1 thylakoid (membrane) ; 3 2 ATP and reduced NADP used to convert GP to TP ; 3 ATP used in regeneration of RuBP ; © Cambridge University Press & Assessment 2026 Page 25 of 25

4(a) any four from: 4 1 (put) extract / sample / concentrate / pigments, on, 2 e.g. ethanol / acetone / petroleum ether + pencil / base, line ; hexane / trichloromethane 2 (named) solvent below, extract / line, and idea of time to 2 DO NOT ALLOW water rise / left till solvent rises / wait till solvent almost reaches top ; 5 ALLOW database / standard values 3 remove paper (before solvent reaches end) and mark solvent front ; 4 (R =) distance pigment moved ÷ distance solvent moved ; f 5 check / compare with, known / reference / published, data / values ; 4(b) any three from: 3 IGNORE colours throughout 1 absorb light ; 1 ALLOW harvest / capture / trap, for ‘absorb’ 2 for, light dependent 2 IGNORE photolysis (stage) / photophosphorylation / photoactivation ; 2 CON if process described with error e.g. pigment passes 3 absorb / use, more / different, wavelengths electrons to another pigment OR (different pigments have) different / extend, absorption spectra ; 4 e.g. chlorophyll a is, primary pigment / reaction centre and, 4 AVP ; carotene / xanthophyll / chlorophyll b, are accessory pigments e.g. (some pigments may) protect from excess light © Cambridge University Press & Assessment 2026 Page 12 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/

7(a)(i) (92 – 35) ÷ 35  100 OR (57 ÷ 35)  100 ; 2 163 (%) ; ECF answer to 3 s.f. from correct working with mis-read graph figures (from bars or trend line) e.g. if (63 – 3) ÷ 3  100 ALLOW 2000 ECF 7(a)(ii) LIST RULE APPLIES but IGNORE incompletely named 4 ALLOW 1 mark for ‘limiting factor for / limits rate of / affects factors rate of, photosynthesis’ if 2R / 4R / 6R not given any two pairs of a factor (F) and reason (R) from: 1F light intensity ; 2R ALLOW limiting factor for ‘limits rate of’ 2R limits / affects, rate of, light-dependent 2R ALLOW description e.g. if light intensity is higher stage / photophosphorylation / photoactivation ; photophosphorylation, increases / occurs more / is faster 3F carbon dioxide concentration ; 4R ALLOW limiting factor for ‘limits rate of’ 4R limits / affects, rate of, light independent stage / Calvin 4R ALLOW description cycle / carboxylation / carbon fixation ; 5F temperature ; 6R ALLOW limiting factor for ‘limits rate of’ 6R limits / affects, rate of, (named) enzyme-catalysed 6R ALLOW description reactions / formation of enzyme-substrate complexes / Calvin 6R IGNORE high temperature denatures enzymes cycle / light independent stage / photolysis ; 6R CON low temperature denatures enzymes 7F (concentration in water of) nitrate / phosphate / (other 7F AVP ; named) mineral ion / mineral nutrients / dissolved oxygen OR fertiliser run-off / sewage discharge (into water / ocean) OR (water / ocean) pH 8R AVP ; 8R linked to, role in metabolism / named organic molecule © Cambridge University Press & Assessment 2026 Page 18 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/ 7(b) any four from: 4 IGNORE SR, troponin, tropomyosin, actin, myosin ECF after first error of each type: ‘into membrane’, wrong ion symbol, omitting to state ion ECF for ‘less’ instead of ‘no’ after first error 1 sodium ions / Na+, do not enter, motor neurone / axon ; 1 ALLOW Na+ moves in at ligand-gated channels only 1 DO NOT ALLOW Na+ enter membrane for ‘enter neurone’ 1 DO NOT ALLOW toxin, mimics ACh / binds to ACh receptors (i.e. affects ligand-gated channel) 2 no, propagation / transmission / passing on, of, 2 ALLOW impulse, not sent to / doesn’t reach, synaptic knob depolarisation / action potential / impulse ; 3 no Ca2+ enter, synaptic knob / presynaptic neurone ; 3 ALLOW Ca2+ channels don’t open at, synaptic knob / presynaptic neurone 4 no acetylcholine, release / exocytosis ; 4 ALLOW ACh 4 ALLOW acetylcholine does not diffuse across, cleft / neuromuscular junction / synapse 5 no, stimulation of / depolarisation of / binding of 5 ALLOW muscle cell membrane / postsynaptic membrane, acetylcholine to, sarcolemma ; for ‘sarcolemma’ 5 DO NOT ALLOW membrane of postsynaptic knob / postsynaptic neurone 5 DO NOT ALLOW toxin, mimics acetylcholine / binds to acetylcholine receptors (i.e. affects ligand-gated channel) but ECF from mp1 6 no, T-tubule, depolarisation / action potential / impulse transmission ; © Cambridge University Press & Assessment 2026 Page 19 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/

10(a) any four from: 4 structure function in photosynthesis 1 stroma site of, (enzymes in) light-independent stage / Calvin cycle ; site of, light-dependent stage / photosystems / 2 ; (named) pigments / oxygen-evolving complex thylakoid membranes contains, electron transport chain / ETC / ATP 3 ; synthase / electron carriers to contain many, (named) pigment / photosystems grana / 4 or ; granum increase surface area for light (energy) absorption thylakoid, ref. to setting up proton gradient / contains a high 5 space / ; concentration of protons lumen 6 DNA codes for (named) proteins / ribosomes ; 7 ribosomes translation (of mRNA) into / production of, (named) proteins ; 10(b)(i) B = 0.42 ; 1 10(b)(ii) A = carotene 1 B = chlorophyll b ; © Cambridge University Press & Assessment 2026 Page 22 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/ 10(b)(iii) any two from: 2 1 act as accessory pigments ; Ignore secondary pigments 2 absorbs light wavelengths not absorbed by, reaction centre / primary pigment / chlorophyll a ; 3 so extends the range of wavelengths absorbed ; 4 pass energy to, reaction centre / primary pigment / chlorophyll a ; © Cambridge University Press & Assessment 2026 Page 23 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/

10(a) any four from: 4 1 electrons emitted (from chlorophyll) ; A electrons excited 2 electrons pass along, electron transport chain / ETC, releasing energy ; 3 (energy is used to) pump protons into thylakoid space ; 4 ref. to proton gradient ; 5 protons pass through ATP synthase into stroma ; 6 ATP produced from ADP and Pi ; 10(b)(i) ribulose bisphosphate ; 2 triose phosphate ; 10(b)(ii) causes reduction ; A reduced NADP is oxidised 2 (so) converts GP to TP ; 10(b)(iii) amino acid ; Ignore proteins 1 © Cambridge University Press & Assessment 2026 Page 19 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/ 10(c) 1 carbon dioxide concentration is the limiting factor when, rate is increasing / AW ; 3 2 as graph levels off another factor becomes limiting ; 3 temperature / light intensity (become limiting) ; 4 AVP ; e.g. water shortage (closes stomata) causing low(er) concentration of carbon dioxide ; © Cambridge University Press & Assessment 2026 Page 20 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/

6(a) S ; 2 P ; 6(b)(i) 0.0044 ; 2 23 ; 6(b)(ii) 1 as light intensity increases rate of photosynthesis increases / AW ; 4 2 data quote – 2 light intensities and 2 rates of photosynthesis plus units ; relative light intensity rate of photosynthesis / min-1 0.0400 43.5 0.0025 11.4 difference 0.0375 difference 32.1 3 (photosynthesis takes place so) oxygen produced, collects / stays, inside disc / on surface of disc ; 4 disc, less dense / more buoyant / float ; 6(b)(iii) 1 light intensity no longer limiting ; 2 2 carbon dioxide concentration / temperature, now limiting ; © Cambridge University Press & Assessment 2026 Page 16 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/