The end product of glycolysis is pyruvic acid whereas acetyl CoA is the connecting link between glycolysis and Krebs' cycle. The TCA cycle was first described by Krebs, 1937 as a cyclic process in which acetyl coA is oxidised to CO2 and water. Acetyl CoA combines with oxalo acetic acid to form citric acid. After a series of cyclic reactions OAA is recycled back.

The correct end product of the citric acid/Krebs cycle is carbon dioxide (CO2) and water (H2O).

The citric acid cycle, also known as the Krebs cycle or tricarboxylic acid cycle, is a series of chemical reactions that occur in the mitochondria of cells. It is an essential part of cellular respiration and plays a crucial role in the production of energy in the form of ATP.

The citric acid cycle begins with the conversion of a two-carbon molecule, acetyl-CoA, into a four-carbon molecule, citric acid. This is achieved through the condensation of acetyl-CoA with oxaloacetate, a four-carbon molecule. The enzyme responsible for this reaction is citrate synthase.

Once citric acid is formed, it undergoes a series of reactions that involve the release of carbon dioxide and the production of reduced electron carriers, such as NADH and FADH2. These electron carriers are essential for the generation of ATP in the subsequent oxidative phosphorylation step.

The citric acid cycle involves several key enzymes and reactions, including isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase complex, succinyl-CoA synthetase, and malate dehydrogenase, among others. These enzymes catalyze the conversion of citric acid to isocitrate, alpha-ketoglutarate, succinyl-CoA, fumarate, and malate, respectively.

The final step of the citric acid cycle involves the regeneration of oxaloacetate, which is necessary to start the cycle again. During this step, malate is oxidized to oxaloacetate by the enzyme malate dehydrogenase, producing NADH in the process.

Overall, the citric acid/Krebs cycle produces three molecules of NADH, one molecule of FADH2, and one molecule of GTP (which can be converted to ATP). Carbon dioxide is released as a waste product during the cycle. These reduced electron carriers, NADH and FADH2, play a crucial role in the electron transport chain, where they donate electrons to generate ATP through oxidative phosphorylation.

In conclusion, the end product of the citric acid/Krebs cycle is carbon dioxide (CO2) and water (H2O).