Describe the process of cyclic photophosphorylation and the structure of the photosystem involved.

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2018). The mark or mark type is shown in brackets.

1. [9] any nine from:
2. cyclic photophosphorylation:
3. 1 (only) PSI / P700, involved ;
4. 2 light energy absorbed ;
5. 3 (results in) electron excited / AW ;
6. 4 (electron) emitted from chlorophyll ;
7. 5 chain of electron carriers / ETC;
8. 6 ATP synthesis ;
9. 7 electron returns to, PSI / P700;
10. photosystems:
11. 8 pigments arranged in light-harvesting clusters ;
12. 9 primary pigment / chlorophyll a / reaction centre ;
13. 10 accessory pigments / chlorophyll b / carotenoids, surround, primary pigment / reaction centre / chlorophyll a ;
14. 11 photosystem located in thylakoid;
15. [6] any six from:
16. formation:
17. 1 both photosystems involved ;
18. 2 photolysis of water ;
19. 3 H⁺ released from, PSII / P680;
20. 4 e⁻ released from, PSI / P700 ;
21. 5 e⁻ and H⁺ / both, combine with NADP (to form reduced NADP) ;
22. use:
23. 6 reduces GP / AW ;
24. 7 TP formed ;
25. 8 (takes place in) stroma;