Question

1. what happens to acetyl coa when it first enters the citric acid cycle? 2. carbon dioxide is produced from the citric acid cycle. from what molecule do the carbon atoms originally come from? 3. oxaloacetate is used in the first step of the citric acid cycle. where does it come from? is acetyl coa the only molecule that is used in the citric acid cycle? if not, what other molecule(s) can enter the cycle?

Explanation:

1. When Acetyl - CoA first enters the Citric acid cycle, it combines with oxaloacetate to form citrate. This is a key initial step in the cycle's operation for energy production.
2. The carbon atoms in the carbon dioxide produced from the Citric acid cycle originally come from Acetyl - CoA. As the cycle progresses, the carbon atoms are gradually released as CO₂.
3. Oxaloacetate is regenerated at the end of the Citric acid cycle and can be used again in the first step. Acetyl - CoA is not the only molecule that can enter the cycle; other molecules such as certain amino acids and fatty - acid breakdown products can also be converted into intermediates that enter the Citric acid cycle.

Answer:

1. It combines with oxaloacetate to form citrate.
2. They come from Acetyl - CoA.
3. It is regenerated at the end of the cycle. No, other molecules like certain amino acids and fatty - acid breakdown products can also enter.