AP BIOLOGY

Detailed explanation-1: -The Krebs cycle itself actually begins when acetyl-CoA combines with a four-carbon molecule called OAA (oxaloacetate) (see Figure above). This produces citric acid, which has six carbonatoms. This is why the Krebs cycle is also called the citric acid cycle.

Detailed explanation-2: -At the end of this series of reactions, the four-carbon starting molecule, oxaloacetate, is regenerated, allowing the cycle to begin again.

Detailed explanation-3: -Answer and Explanation: Oxaloacetate is one of the essential intermediates of the Krebs cycle. It results in the formation of the citrate after reacting with acetyl-CoA. Citrate synthase plays a significant role in catalyzing carrying out this reaction.

Detailed explanation-4: -In the eigth and last step of the citric acid cycle, oxaloacetate is regenerated from malate by malate dehydrogenase so it can once again combine with acetyl CoA and keep the cycle going.

Detailed explanation-5: -Oxaloacetate is regenerated at the end of the cycle. For each glucose that enters glycolysis, products of the citric acid cycle are 2 ATP, 6 NADH, and 2 FADH2.