AP BIOLOGY

Detailed explanation-1: -Oxaloacetate is a four-carbon organic molecule produced at the last step of the Krebs cycle (TCA cycle). TCA cycle helps to produce energy-rich molecules such as ATP, NADH, etc., for fulfilling the energy requirements of the cell.

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: -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-4: -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.

Detailed explanation-5: -Oxaloacetate is an intermediate of the citric acid cycle, where it reacts with acetyl-CoA to form citrate, catalyzed by citrate synthase. It is also involved in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, and fatty acid synthesis. Oxaloacetate is also a potent inhibitor of complex II.