Citric Acid Cycle Count: NADH, FADH2, GTP and CO2 per Glucose

One acetyl-CoA enters the citric acid cycle per turn. One glucose gives two pyruvate, then two acetyl-CoA, so the cycle turns twice per glucose.

Per turn and per glucose

Where each one comes from: NADH at isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase and malate dehydrogenase; GTP at succinyl-CoA synthetase; FADH2 at succinate dehydrogenase; CO2 at the first two NADH steps.

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Include the steps before the cycle

The pyruvate dehydrogenase complex makes 1 NADH and 1 CO2 per pyruvate, so 2 NADH and 2 CO2 per glucose, before the cycle starts. That is not part of the cycle itself, so check whether a question says "in the cycle" or "from pyruvate."

Common traps

• Forgetting the doubling. Per glucose is twice per turn.
• Counting the cycle's carbon. The two carbons of acetyl-CoA are not the two carbons released as CO2 in that same turn.
• Calling the PDH step part of the cycle. It is the link reaction.
• Counting GTP as zero ATP. GTP is energetically equivalent to ATP.

One-minute recap

• Per turn: 3 NADH, 1 FADH2, 1 GTP, 2 CO2.
• Per glucose: 6, 2, 2, 4.
• Add 2 NADH and 2 CO2 from PDH if the question starts at pyruvate.