Which statement best describes aerobic and anaerobic respiration?

• A. Aerobic respiration uses oxygen and yields about 36-38 ATP per glucose.
• B. Aerobic respiration uses no oxygen and yields about 36-38 ATP.
• C. Anaerobic respiration uses oxygen and yields 2 ATP.
• D. Both pathways produce the same ATP yield and neither requires oxygen.

Answer: (A)

Think about how cells harvest energy from glucose and the role of oxygen. In aerobic respiration, oxygen acts as the final electron acceptor in the electron transport chain, which powers oxidative phosphorylation and produces the bulk of ATP. Because this process fully oxidizes glucose to CO2 and H2O, the typical energy yield is about 36–38 ATP per glucose in many cells. In contrast, anaerobic pathways operate without oxygen. They rely on glycolysis plus fermentation to regenerate NAD+, but they don’t run the full oxidative phosphorylation system, so the total ATP yield is only about 2 ATP per glucose. The other statements contradict these ideas—one incorrectly claims no oxygen is used for aerobic respiration, and another wrongly says both pathways produce the same ATP and neither requires oxygen.