"Which statement about the citric acid cycle is false?" a) CO2 is released during operation of the cycle. b) It takes place in the mitochondrial matrix. c) It does not operate under anaerobic conditions. d) It requires NAD+ and FAD.e) It releases less energy than glycolysis.

The citric acid cycle is the second stage of cellular respiration. Under aerobic conditions, each of the pyruvate formed by the glycolytic breakdown of one glucose molecule enters a citric acid cycle in the form of acetyl CoA. Complete oxidative decarboxylation of acetyl CoA occurs and the carbon skeleton of pyruvate is released in the form of CO2. The energy released during oxidative decarboxylation is stored in the form of 6 NADH and 2 FADH2 per glucose. In addition, substrate-level phosphorylation during the citric acid cycle also forms 2 ATP per glucose molecule.

During glycolysis, the net yield is 2 ATP and 2 NADH per glucose. Therefore, the ATP gain for glycolysis and the citric acid cycle is equal. Citric acid cycle stores most of the energy of glucose into NADH and FADH2 which are oxidized by electron transport chain and drive the synthesis of a large number of ATP molecules.