Questions: The carbon dioxide produced during the citric acid cycle is derived from O coenzyme A O citric acid () pyruvate o oxygen

The answer is the third one: pyruvate.

Explanation for each option:

• Coenzyme A: This is incorrect. Coenzyme A is involved in the transport of acetyl groups into the citric acid cycle, but it is not the source of carbon dioxide. It acts as a carrier molecule and does not directly contribute carbon atoms that are released as CO2.

• Citric acid: This is incorrect. While citric acid (citrate) is a key intermediate in the citric acid cycle, the carbon dioxide produced during the cycle is not directly derived from citric acid itself. Instead, it comes from the decarboxylation of intermediates that originate from pyruvate.

• Pyruvate: This is correct. Pyruvate, which is the end product of glycolysis, is converted into acetyl-CoA before entering the citric acid cycle. During this conversion, one molecule of CO2 is released. Additionally, within the citric acid cycle, further decarboxylation reactions release more CO2, which originally came from the pyruvate.

• Oxygen: This is incorrect. Oxygen is not a source of carbon dioxide in the citric acid cycle. Instead, oxygen is the final electron acceptor in the electron transport chain, which is a separate process from the citric acid cycle.

In summary, the carbon dioxide produced during the citric acid cycle is derived from pyruvate, which is converted into acetyl-CoA and further metabolized within the cycle.