Question

During the citric acid cycle: A. ATP is synthesized by substrate level phosphorylation. B. ATP is synthesized by oxidative phosphorylation. C. carbon-containing molecules are completely reduced. D. high-energy electrons are removed from NAD and FADH.

Answer 1

A. ATP is synthesized by substrate level phosphorylation.

Step-by-step explanation:

The citric acid cycle includes complete oxidation of acetyl CoA into CO2 and H2O. The electrons released during the reactions reduce NAD and FAD into NADH and FADH2 respectively. During the citric acid cycle, alpha-ketoglutarate is decarboxylated into succinyl CoA. This is oxidation as well. The succinyl CoA is then converted into succinate and ADP phosphorylation occurs. Since the energy required for the phosphorylation of ADP into ATP is provided by the oxidative decarboxylation of alpha-ketoglutarate, it represents the substrate-level phosphorylation. This forms two ATP molecules per glucose during the citric acid cycle.