In the process of glycolysis (EMP pathway), one molecule of glucose breaks down into two molecules of pyruvic acid by 10-step reaction in cytoplasm of cell. The glycolysis is common to both aerobic and anaerobic respiration. There is a net gain of eight ATP molecules in glycolysis, ie, two ATP from direct phosphorylation and six ATP from two molecules of NADH2 in an electron transport chain. Carbon dioxide is released in Krebs cycle of respiration. Two molecules of carbon dioxide released in each cycle. One molecule of FADH2 is formed in Krebs cycle. On oxidation, one molecule of FADH2 provides two ATP instead of three in NADH2 . NADPH2 takes part in anabolic process and pentose phosphate pathway.