ATP is synthesised from ADP and Pᵢ in a phosphorylation reaction.

Mark scheme

Marking points from the official mark scheme (May/June 2022). The mark or mark type is shown in brackets.

1. any two from: substrate-linked (phosphorylation) ; A substrate level phosphorylation
2. chemiosmosis / oxidative (phosphorylation);
3. any six from: 1 hydrogen / electron, carriers ; R hydrogen ions / hydrogen molecules
4. 2 in glycolysis NAD becomes reduced ;
5. 3 (so that) triose phosphate becomes, oxidised / dehydrogenated ;
6. 4 in the link reaction NAD becomes reduced ;
7. 5 (so that) pyruvate becomes, oxidised / dehydrogenated or for production of acetyl coenzyme A ;
8. 6 in the Krebs cycle both NAD and FAD become reduced ;
9. 7 to regenerate oxaloacetate;
10. 8 (deliver, hydrogen / H+ and e¯), to inner mitochondrial membrane / to cristae / to ETC / for oxidative phosphorylation / for chemiosmosis;
11. 9 ref. to ATP production ;
12. 10 ref. to recycling of, NAD / FAD ;
13. any two from: 1 ref. to increase / decrease / control, of (rate of the) link reaction ;
14. 2 allows build-up of acetyl CoA to be used in the Krebs cycle ;
15. 3 enzyme becomes active again when, coenzyme A increases / ratio falls ;
16. 4 allows more coenzyme A, to enter / return to, the link reaction ; A not enough CoA to enter the link reaction ora
17. 5 AVP; e.g. end product inhibition