Which statement describes aerobic and anaerobic respiration?

Which statement describes aerobic and anaerobic respiration?

• A. Aerobic uses oxygen and yields more ATP; anaerobic without oxygen yields less ATP
• B. Anaerobic yields more ATP; aerobic yields less ATP
• C. Both require oxygen, but only aerobic produces carbon dioxide
• D. Anaerobic occurs only in bacteria

Answer: (A)

Oxygen availability changes how energy is extracted from glucose. In aerobic respiration, oxygen serves as the final electron acceptor in the electron transport chain, allowing glucose to be fully oxidized to carbon dioxide and water. This complete breakdown captures a lot of chemical energy, yielding a relatively large amount of ATP—about 30 to 32 per glucose in many cells. If oxygen isn’t present, cells can’t run the full chain. They still get some energy by glycolysis and then regenerate NAD+ through fermentation, but this pathway only yields a small amount of ATP—roughly 2 per glucose. That’s why aerobic respiration produces much more ATP than anaerobic processes. So the statement that aerobic respiration uses oxygen and yields more ATP, while anaerobic respiration occurs without oxygen and yields less ATP, best describes how these two processes differ. The other options misstate either the role of oxygen, the energy yield, or where fermentation fits in, and aren’t generally accurate.

Oxygen availability changes how energy is extracted from glucose. In aerobic respiration, oxygen serves as the final electron acceptor in the electron transport chain, allowing glucose to be fully oxidized to carbon dioxide and water. This complete breakdown captures a lot of chemical energy, yielding a relatively large amount of ATP—about 30 to 32 per glucose in many cells.

If oxygen isn’t present, cells can’t run the full chain. They still get some energy by glycolysis and then regenerate NAD+ through fermentation, but this pathway only yields a small amount of ATP—roughly 2 per glucose. That’s why aerobic respiration produces much more ATP than anaerobic processes.

So the statement that aerobic respiration uses oxygen and yields more ATP, while anaerobic respiration occurs without oxygen and yields less ATP, best describes how these two processes differ. The other options misstate either the role of oxygen, the energy yield, or where fermentation fits in, and aren’t generally accurate.