Per turn of the citric acid cycle (per acetyl-CoA), how many NADH, FADH2, and CO2 molecules are produced?

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Multiple Choice

Per turn of the citric acid cycle (per acetyl-CoA), how many NADH, FADH2, and CO2 molecules are produced?

This question tests the stoichiometry of the citric acid cycle per acetyl-CoA turn. As acetyl-CoA enters the cycle and is oxidized, three NADH molecules are produced at three separate dehydrogenase steps: isocitrate to α-ketoglutarate, α-ketoglutarate to succinyl-CoA, and malate to oxaloacetate. One FADH2 is formed when succinate is converted to fumarate by succinate dehydrogenase. Two CO2 molecules are released during decarboxylation steps: isocitrate to α-ketoglutarate and α-ketoglutarate to succinyl-CoA. In addition, a GTP (or ATP) is generated via substrate-level phosphorylation during conversion of succinyl-CoA to succinate, though that product isn’t part of the question. So per acetyl-CoA turn, you get three NADH, one FADH2, and two CO2.

This question tests the stoichiometry of the citric acid cycle per acetyl-CoA turn. As acetyl-CoA enters the cycle and is oxidized, three NADH molecules are produced at three separate dehydrogenase steps: isocitrate to α-ketoglutarate, α-ketoglutarate to succinyl-CoA, and malate to oxaloacetate. One FADH2 is formed when succinate is converted to fumarate by succinate dehydrogenase. Two CO2 molecules are released during decarboxylation steps: isocitrate to α-ketoglutarate and α-ketoglutarate to succinyl-CoA. In addition, a GTP (or ATP) is generated via substrate-level phosphorylation during conversion of succinyl-CoA to succinate, though that product isn’t part of the question. So per acetyl-CoA turn, you get three NADH, one FADH2, and two CO2.

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