The pyruvic acid from glycolysis can be converted to acetic acid, which can enter the citric acid cycle. Because this process is
a cycle, the atoms entering the cycle must balance the atoms that leave. Consider carbon balance in the citric acid cycle. How many CO 2 molecules leave the cycle for each acetic acid molecule that enters? For this question, assume that carbon only enters as acetic acid and exits as CO 2 . Note that acetic acid has two carbon atoms. You can determine the number of carbon atoms in carbon dioxide from its formula, CO 2 .
During glycolysis one molecule of glucose is oxidized to two molecules of pyruvic acid (3 carbon molecule). Pyruvic acid is converted to acetyl CoA(2 carbon molecule) by the pyruvate dehydrogenase complex.
For each acetic acid that enters the citric acid cycle 2 molecules of CO2 is given off.
For one glucose molecule produces 2 acetyl CoA
2 acetyl groups + 6 NAD+ + 2 FAD + 2 ADP + 2 Pi yields 4 CO2 + 6 NADH + 6 H+ + 2 FADH2 + 2 ATP.
Hence 4 molecules of acetic acid is completely oxidized to 8 molecules of CO2.
