Why would an organism carry out fermentation instead of aerobic respiration?

• A. Because oxygen is unavailable as a final electron acceptor
• B. Because fermentation allows for the complete oxidation of glucose
• C. Because fermentation requires the presence of mitochondria
• D. Because fermentation produces more ATP than aerobic respiration

Answer: (A)

Verified step by step guidance

1. Understand the context of the question: Fermentation and aerobic respiration are two different metabolic pathways used by organisms to generate energy (ATP). Aerobic respiration requires oxygen, while fermentation does not.
2. Recall the role of oxygen in aerobic respiration: Oxygen acts as the final electron acceptor in the electron transport chain, allowing for efficient ATP production. Without oxygen, this process cannot occur.
3. Consider the conditions under which fermentation occurs: Fermentation is an anaerobic process, meaning it takes place in the absence of oxygen. It allows cells to regenerate NAD⁺, which is necessary for glycolysis to continue.
4. Compare ATP production in fermentation and aerobic respiration: Aerobic respiration produces significantly more ATP (approximately 36-38 ATP per glucose molecule) compared to fermentation, which typically produces only 2 ATP per glucose molecule.
5. Evaluate the options provided: The correct answer is 'Because oxygen is unavailable as a final electron acceptor,' as fermentation is a backup pathway used when oxygen is not present to sustain energy production.