The Fates of Pyruvate In terms of energy, the result of glycolysis is the production of two ATPs and two NADHs per molecule of glucose. Pyruvate, the other product of glycolysis, is still an energy-rich molecule, which can yield a substantial amount of ATP. Whether or not further energy can be produced, however, depends on the cell type and the availability of oxygen. Under aerobic conditions, most cells in the body convert pyruvate into acetyl-CoA, the entry-level substrate for the citric acid cycle, an amphibolic pathway that completely oxidizes the two acetyl carbons to form CO2 and and the reduced molecules NADH and FADH2. (An amphibolic pathwayfunctions in both anabolic and catabolic processes.) The electron transport system, a series of oxidation- reduction reactions, transfers electrons from NADH and FADH2 to O2 to form water. The energy that is released during electron transport is coupled to a mechanism that synthesizes ATP. Under anaerobic conditions, further oxidation of pyruvate is impeded. A number of cells and organisms compensate by converting this molecule to a more reduced organic compound and regenerating the NAD required for glycolysis to continue (Figure 8.6).