AP BIOLOGY

Detailed explanation-1: -The Kreb’s Cycle is an aerobic process consisting of eight definite steps. In order to enter the Kreb’s Cycle pyruvate must first be converted into Acetyl-CoA by pyruvate dehydrogenase complex found in the mitochondria.

Detailed explanation-2: -Cellular Respiration Stage II: The Krebs Cycle. Recall that glycolysis, stage I of cellular respiration, produces two molecules of pyruvate (also known as pyruvic acid). These molecules enter the matrix of a mitochondrion, where they start the Krebs cycle.

Detailed explanation-3: -Answer and Explanation: The molecules that can enter the Krebs or Citric Acid cycle are Acetyl CoA. Acetyl CoA is made in an intermediate step between glycolysis and the Krebs cycle.

Detailed explanation-4: -Hence the correct answer is the option ‘The cycle starts with condensation of an acetyl group (acetyl CoA) with pyruvic acid to yield citric acid’.