AP BIOLOGY

Detailed explanation-1: -In the Krebs cycle, acetyl coenzyme A produced by the link reaction joins the 4-carbon compound oxaloacetic acid (or oxaloacetate) to form the 6-carbon compound citric acid (or citrate). Then, in a series of reactions, oxaloacetic acid is regenerated from citric acid.

Detailed explanation-2: -Key Points. The citric acid cycle is also known as the Krebs cycle or the TCA (tricarboxylic acid) cycle. Acetyl CoA transfers its acetyl group to oxaloacetate to form citrate and begin the citric acid cycle. The release of carbon dioxide is coupled with the reduction of NAD+ to NADH in the citric acid cycle.

Detailed explanation-3: -Acetyl CoA from the link reaction reacts with a four-carbon molecule called oxaloacetate. The coenzyme A portion of acetyl CoA is removed and returns to the link reaction to be reused. A 6-carbon molecule called citrate is produced. Carbon and hydrogen are removed from citrate, forming carbon dioxide and reduced NAD.

Detailed explanation-4: -Acetyl-CoA then enters the citric acid cycle, where the acetyl group is oxidized to carbon dioxide and water, and the energy released is captured in the form of 11 ATP and one GTP per acetyl group.

Detailed explanation-5: -The end product of the link reaction, acetyl-coenzyme A, then enters into the Krebs Cycle. The purpose of the Krebs Cycle is to produce energy through the oxidation of acetyl-coenzyme A.