Principles of Biochemistry

Under aerobic condition, pyruvate is taken up into mitochondria, and after conversion to acety-CoA is oxidized to CO2 by the citric acid cycle. The reducing equivalents from the NADH+H+ formed in glycolysis are taken up into mitochondria for oxidation.

Two triosephosphates are produced from each molecule of hexose metabolized. Dihydroxyacetone phosphate can be isomerized by isomerase to glyceraldehyde 3 phosphate which is then converted to 1, 3 diphosphoglyceric acid by glyceraldehyde 3 phosphate dehydrogenase system requiring NAD⁺ and inorganic phosphate. From this high-energy compound and from phosphoenol pyruvate another high energy compound derived from it, two ATP molecules can be obtained from ADP present in the cell. Since two molecules of triose phosphates are undergoing the above reaction totally four ATP molcules of produced.

The NADH formed by the dehydrogenation of glyceraldehyde 3 phosphate is then rexoidised to NAD+ by O2 via Electron transport chain of mitochondria and produce 3ATP molecules. Since two molecules of glyceraldehyde 3 phosphate are involved in the above reaction six ATP molecules are produced.However, two ATP molecules are used up in the production of glucose-6-phosphate from glucose and fructose-1, 6-Bisphosphate from fructose-6-phosphate. The net production of ATP is thus only two ATP molecules per mole of glucose during anaerobic glycolysis or fermentation.

b. Under anaerobic condition