A-LevelBiologyPhotosynthesis9700/41 · May/June 2024 · Q513 Marks

Photosynthesis is the energy transfer process that occurs in chloroplasts. Fig. 5.1 shows some biochemical events that occur in a chloroplast during the light-dependent stage of photosynthesis. Photosystems I and II (PSI and PSII) and some associated proteins of the thylakoid membrane are shown. [Figure 5.1]

(a)(i)A and B are areas of the chloroplast. Name areas A and B. A B[2]
(a)(ii)The group of proteins labelled C, PSI and the protein labelled E are involved in a specific biochemical process during the light-dependent stage of photosynthesis. Name this specific biochemical process and the protein labelled E. process E[2]
(a)(iii)Product D is used during the Calvin cycle. Identify product D and describe its specific role in the Calvin cycle.[3]
(b)(i)Limiting factors affect the rate of photosynthesis. Describe and suggest how the results for tropical forest, temperate forest and snow forest in Fig. 5.2 show the effect of limiting factors on photosynthesis.[3]
(b)(ii)Suggest reasons why grasslands and desert have a lower rate of energy transfer by photosynthesis than forests.[3]

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Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

[1] (a)(i) A = stroma;
[1] (a)(i) B = thylakoid, lumen / space ;
[1] (a)(ii) cyclic photophosphorylation ;
[1] (a)(ii) ATP synth(et)ase;
[1] (a)(iii) D = reduced NADP ;
[1] (a)(iii) reduces / gives hydrogen to, glycerate (3) phosphate / GP ;
[1] (a)(iii) forming, triose phosphate / TP ;
[1] (b)(i) rate of energy transfer, higher / highest, for tropical or rate of energy transfer, lower / lowest, for snow forest ;
[1] (b)(i) paired data quote with units (at least once);
[1] (b)(i) tropical forest has, high(er/est) temperature / hot(ter);
[1] (b)(i) tropical forest has high(er/est) light, intensity / duration ;
[1] (b)(i) temperature / light intensity, is a limiting factor (on photosynthesis) ;
[1] (b)(ii) more, transpiration / water loss (from leaves) ;
[1] (b)(ii) stomata shut reducing, carbon dioxide (entry) / gas exchange ;
[1] (b)(ii) (so) carbon dioxide (concentration) is a limiting factor ;
[1] (b)(ii) (grassland / desert) fewer plants / less plant cover / smaller plants ;
[1] (b)(ii) (so smaller surface area) less light absorbed ;
[1] (b)(ii) AVP;

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