Final answer:
The final electron acceptor in the process of oxidative phosphorylation in cellular respiration is an oxygen molecule. In the absence of oxygen, living systems can use organic or inorganic molecules as alternative electron acceptors.
Step-by-step explanation:
In aerobic respiration, the final electron acceptor is an oxygen molecule, O2. Oxygen serves as the final electron acceptor at the end of the electron transport chain in oxidative phosphorylation. When aerobic respiration occurs, high-energy electrons carried by NADH or FADH2 are transferred to the electron transport chain, which ultimately results in the production of ATP. If oxygen is not present, some living systems use an organic molecule as the final electron acceptor, while others use an inorganic molecule.