AP BIOLOGY

Detailed explanation-1: -Note that the carbons removed become carbon dioxide, accounting for two of the six such end products of glucose oxidation. The energy released by this breakdown is carried by NADH. The Krebs cycle completes the breakdown of glucose begun in glycolysis.

Detailed explanation-2: -The Krebs cycle, by itself, does not require the presence of oxygen; this element is necessary for the last stage of aerobic cellular respiration, i.e., oxidative phosphorylation. Organic molecules endowed with energy (carbohydrates, lipids, proteins) are split in previous reactions.

Detailed explanation-3: -Thus, if oxygen is not present, the respiratory cycle cannot function, which shuts down the Krebs cycle. For this reason, the Krebs cycle is considered an aerobic pathway for energy production.

Detailed explanation-4: -The Krebs cycle takes place in the mitochondria of the cell. It is a sequence of chemical reactions the cell uses to produce energy during the so-called aerobic respiration.