Question

The graphic shows the citric acid cycle.

A diagram of the citric acid cycle is shown. Acetyl C o A enters the citric acid cycle and combines with a 4-carbon compound to form citric acid.

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

Answer 1

Correct answer: 2

Explanation: The acetyl (2‑carbon) from acetyl‑CoA combines with a 4‑carbon oxaloacetate to form citrate (6 carbons). Through a series of oxidations (producing NADH, FADH2 and GTP/ATP) two CO2 are released and oxaloacetate is regenerated to accept another acetyl group.