In aerobic respiration, most ATP is produced by oxidative phosphorylation. (a) Outline the features of ATP that make it suitable as the universal energy currency.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.

1. [3] (a) any three from: 1 breaks down / hydrolyses to / converted to, ADP/AMP, and Pi ; 2 releases energy / energy donor ; 3 reversible reaction / high turnover / can be regenerated; 4 small / soluble, so can, diffuse / move (freely), in cell; 5 AVP;
2. [6] (b) any six from: 1 ETC/electron flow, less / stops ; 2 no/less, energy, available / released / supplied (from electron flow); 3 no / fewer, H+ ions / protons, pumped to intermembrane space ; 4 no / smaller, H+ / proton, gradient ; 5 no/fewer, protons diffuse through ATP synthase ; 6 no/fewer, electrons reach, last carrier / end of chain; 7 no/fewer, electrons can react with oxygen to form water ; 8 (oxidised) NAD not regenerated / lack of NAD ; 9 no/less, glycolysis / link reaction / Krebs cycle; 10 AVP;