AP BIOLOGY

Detailed explanation-1: -The Krebs cycle is the second phase in cellular respiration. It occurs in the mitochondria in the cell. The number of ATP molecules produced in the Krebs cycle is 2.

Detailed explanation-2: -Considering these 3 molecules of ATP, the total ATP synthesized by one turn of Krebs cycle is (12+3) i.e., 15 molecules of ATP.

Detailed explanation-3: -Because for each glucose molecule there are two pyruvic acid molecules entering the system, two ATP molecules are formed. Also during the Krebs cycle, the two carbon atoms of acetyl-CoA are released, and each forms a carbon dioxide molecule.

Detailed explanation-4: -Two molecules of acetyl-CoA are produced from each glucose molecule so two turns of the Krebs cycle are required which yields four CO2, six NADH, two FADH2 and two ATPs.

Detailed explanation-5: -Oxidation of one molecule of glucose molecule during cellular respiration generates 38 ATP molecules-2 from glycolysis, 2 from Krebs cycle, and 34 from the electron transport system. Therefore, two glucose molecules can generate 76 ATP molecules.