Final answer:
The final electron acceptor in cellular respiration is an oxygen molecule, O2. ATP production in aerobic respiration depends on oxygen, while other mechanisms exist for energy production without it.
Step-by-step explanation:
The final electron acceptor in cellular respiration is O2, an oxygen molecule. In aerobic respiration, NADH and FADH₂ carry high-energy electrons to the electron transport chain, where ATP is produced. Without O2, respiration is anaerobic, and NAD+ must be regenerated through other processes like fermentation or using inorganic molecules in anaerobic cellular respiration.