The citric acid cycle begins with which molecule?

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Multiple Choice

The citric acid cycle begins with which molecule?

The key idea is that the citric acid cycle starts when an acetyl group is added to a four-carbon molecule to form citrate. Acetyl-CoA provides that two-carbon unit and combines with oxaloacetate in a reaction catalyzed by citrate synthase to kick off the cycle. NADH and FADH2 are produced later as electrons are transferred in the cycle, not at the very start. Oxaloacetate is the molecule that gets regenerated at the end to accept another acetyl group, but it is not the one that begins the process. So, the molecule that begins the cycle is acetyl-CoA.

The key idea is that the citric acid cycle starts when an acetyl group is added to a four-carbon molecule to form citrate. Acetyl-CoA provides that two-carbon unit and combines with oxaloacetate in a reaction catalyzed by citrate synthase to kick off the cycle. NADH and FADH2 are produced later as electrons are transferred in the cycle, not at the very start. Oxaloacetate is the molecule that gets regenerated at the end to accept another acetyl group, but it is not the one that begins the process. So, the molecule that begins the cycle is acetyl-CoA.

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