Question

If 15 original glucose molecules enter catabolism through glycolysis, how many total carbon atoms from all of them would enter the Krebs cycle/TCA cycle/citric acid cycle in the presence of oxygen? How many remaining carbon atoms would be lost as carbon dioxide?

Answer 1

If 15 original glucose molecules enter glycolysis, a total of 60 carbon atoms from all of them would enter the citric acid cycle. 60 carbon atoms would be lost as carbon dioxide.

Step-by-step explanation:

During glycolysis, a glucose molecule is broken down into two molecules of pyruvate. Each pyruvate molecule then enters the citric acid cycle as acetyl CoA. Since there were originally 15 glucose molecules, there would be a total of 30 pyruvate molecules. Therefore, 30 acetyl groups would enter the citric acid cycle. Each acetyl group contributes two carbon atoms, so a total of 60 carbon atoms from all the acetyl groups would enter the citric acid cycle.

During the citric acid cycle, two carbon dioxide molecules are released on each turn of the cycle. As there are two turns of the cycle for each glucose molecule, a total of four carbon dioxide molecules would be released from each glucose molecule. With 15 glucose molecules entering glycolysis, a total of 60 carbon dioxide molecules would be released.