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 CO2 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 CO2 . Note that acetic acid has two carbon atoms. You can determine the number of carbon atoms in carbon dioxide from its formula, CO2 .

The TCA cycle or citric acid cycle is a central pathway of cellular respiration that helps in unifying several metabolites and generates energy for cellular functions. It takes place over eight different steps:

Step 1: Acetyl CoA enters the citric acid cycle that is a 2-carbon compound and attaches with 4-carbon compound oxaloacetate to form citrate a 6 carbon compound

Step 2: This 6-carbon compound isocitrate

Step 3: 5 carbon compound alpha-ketoglutarate is produced by oxidizing the isocitrate and release the release of carbon dioxide. One NADH molecule is formed.

Step 4: This 5 carbon molecule is oxidized again to form a four-carbon compound that binds with CoA to make forming succinyl CoA. A second molecule of NADH is produced, alongside a second molecule of carbon dioxide.

Step 5: Succinyl CoA is then converted to succinate with GTP formation

Step 6: Succinate is converted into fumarate with the generation of FADH₂ molecule.

Step 7: Fumarate is converted to malate

Step 8: oxaloacetate is formed with the NADH molecule.