Final answer:
Oxygen acts as the terminal electron acceptor in the electron transport chain of aerobic respiration by combining with electrons and protons (H+ ions) to form water (H2O).
Step-by-step explanation:
Oxygen acts as the terminal electron acceptor by combining with the electrons and H+ ions to form water.
In the electron transport chain of aerobic respiration, the energy from high-energy electrons carried by NADH or FADH2 is used to produce ATP. This complex biochemical process occurs within the mitochondria of cells. The ultimate acceptor of these electrons, along with free hydrogen ions, is oxygen (O₂). This reaction is essential as it drives the production of ATP, which is the energy currency of the cell. The oxygen, having accepted electrons, then combines with hydrogen ions (H+) to form water (H₂O).
If oxygen weren't available to accept the electrons at the end of the electron transport chain, this would halt the ATP production process, leading to a lack of energy, and eventually, cell death. That is why oxygen is referred to as the terminal electron acceptor; it is crucial for the continuation of the electron transport chain and therefore for the efficient production of ATP. This is also the reason why organisms that undergo aerobic respiration require oxygen to survive.
The correct answer to the question is:
Oxygen acts as the terminal electron acceptor by combining with the electrons and H+ ions to form water.