Q.State the number of molecules of ATP (or its equivalent, GTP) generated by substrate-level phosphorylation in a single turn of the TCA cycle.

The tricarboxylic acid (TCA) cycle, also called the Krebs cycle (after Hans Krebs) or citric acid cycle, is the second stage of aerobic respiration, occurring cyclically in the mitochondrial matrix. Each turn begins when acetyl CoA combines with oxaloacetic acid (via citrate synthase) to form citric acid, which is rearranged to isocitric acid and undergoes two oxidative decarboxylation steps (releasing 2 CO2, generating 2 NADH) via alpha-ketoglutaric acid to succinyl CoA. Succinyl CoA is converted to succinic acid, capturing 1 ATP (as GTP) by substrate-level phosphorylation -- the cycle's only direct ATP-capturing step. Succinic acid is then oxidised (via FAD, generating 1 FADH2) to fumaric acid, hydrated to malic acid, and finally oxidised (generating a further NADH) back to oxaloacetic acid, re …