How many times does the Citric Acid Cycle turn per full sequence of oxidation?

How many times does the Citric Acid Cycle turn per full sequence of oxidation?

• A. 1
• B. 4
• C. 3
• D. 2

Answer: (D)

In the Citric Acid Cycle, each acetyl-CoA that enters the cycle drives one complete pass around the wheel. So the number of turns equals the number of acetyl-CoA molecules feeding the cycle. A full oxidation of one glucose molecule produces two pyruvate molecules from glycolysis, and each pyruvate is converted to acetyl-CoA before entering the cycle. That gives two acetyl-CoA entering the cycle, meaning the cycle turns twice per glucose oxidation. For each turn, energy carriers are produced (3 NADH, 1 FADH2, and 1 GTP) and two CO2 are released, and this happens twice when you start from one glucose.

In the Citric Acid Cycle, each acetyl-CoA that enters the cycle drives one complete pass around the wheel. So the number of turns equals the number of acetyl-CoA molecules feeding the cycle.

A full oxidation of one glucose molecule produces two pyruvate molecules from glycolysis, and each pyruvate is converted to acetyl-CoA before entering the cycle. That gives two acetyl-CoA entering the cycle, meaning the cycle turns twice per glucose oxidation. For each turn, energy carriers are produced (3 NADH, 1 FADH2, and 1 GTP) and two CO2 are released, and this happens twice when you start from one glucose.