AP BIOLOGY

Detailed explanation-1: -The NADH is made at the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) step in the middle of glycolysis. During fermentation, the NADH is used to reduce pyruvate to lactate, which is then excreted. This process results in a net yield of two ATP and two lactate molecules per glucose, without consuming any oxygen.

Detailed explanation-2: -Some organisms, such as some bacteria, will undergo lactate fermentation. Two pyruvates are converted to two lactic acid molecules, which ionize to form lactate. In this process two NADH + H+ are converted to two NAD+. Our muscle cells can undergo this process when they are in oxygen debt.

Detailed explanation-3: -NADH is also formed in the cytosol by glycolysis and lactate oxidation, and subsequently oxidized while being transported into the mitochondria by the malate–aspartate shuttle, or when coupled with the conversion of pyruvate to lactate.

Detailed explanation-4: -Note that this process completely oxidizes 1 molecule of pyruvate, a 3 carbon organic acid, to 3 molecules of CO2. During this process, 4 molecules of NADH, 1 molecule of FADH2, and 1 molecule of GTP (or ATP) are produced.