(a) In aerobic respiration, ATP is synthesised by substrate-linked reactions and by oxidative phosphorylation. Outline the process of oxidative phosphorylation.

Mark scheme

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

1. [7] any seven from: 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 ;
2. [4] any four from: 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 ;