Which of the following is NOT a stage of cellular respiration?

Cellular respiration consists of several key stages that work together to convert glucose into usable energy in the form of ATP. The correct answer identifies fermentation as not being a direct stage of cellular respiration.

Glycolysis is the first step in the process, occurring in the cytoplasm, where glucose is broken down into pyruvate, producing a small amount of ATP and NADH. The Krebs cycle, or citric acid cycle, follows glycolysis if oxygen is present, occurring in the mitochondria. In this cycle, pyruvate is further broken down, releasing carbon dioxide and transferring high-energy electrons to electron carriers like NADH and FADH2.

Oxidative phosphorylation is the final stage, where the electron transport chain and chemiosmosis occur, leading to the production of a significant amount of ATP using the electrons provided by NADH and FADH2 in the presence of oxygen.

Fermentation, while an important metabolic process, is not a stage of cellular respiration. Instead, it serves as an alternative pathway to produce energy anaerobically when oxygen is scarce. Fermentation allows for the continuation of ATP production through glycolysis but does not involve the set of reactions that occur in cellular respiration when oxygen is available. Thus, it