Cellular Respiration — Quiz

Question 7 • Biology

During the citric acid cycle, what happens to acetyl-CoA?

Answer

It enters the citric acid cycle and associates with a 4-carbon molecule, forming citric acid, and then through redox reactions regenerates the 4-carbon molecule.

It enters the citric acid cycle and gains carbon dioxide to form citric acid, and gains more carbon dioxide through redox reactions to form a 4-carbon molecule.

It enters glycolysis and associates with a 5-carbon molecule through redox reactions, forming another acetyl-CoA molecule.

It enters the citric acid cycle and associates with a 4-carbon molecule, forming a 5-carbon compound, and then through oxidation reactions regenerates the 4-carbon molecule.

Explanation

Acetyl-CoA contributes a 2-carbon acetyl group, which combines with the 4-carbon molecule oxaloacetate to form 6-carbon citric acid (citrate). Reactions in the cycle release carbon dioxide and regenerate oxaloacetate, while redox reactions transfer electrons. Choice A describes this overall process; choice D incorrectly says the first compound formed has 5 carbons.

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