What is the primary role of oxygen in the electron transport chain (ETC) of cellular respiration?

The primary role of oxygen in the electron transport chain (ETC) is to accept de-energized electrons at the end of the chain, which is crucial for the process of cellular respiration. As these electrons are passed along the chain, they release energy that is used to pump protons across the mitochondrial membrane, creating a proton gradient.

Oxygen's ability to accept these electrons helps complete the transport chain and leads to the production of water when it combines with the protons (hydrogens) that have also been pumped through the chain. This reaction is vital because it allows the electron transport chain to continue functioning; if oxygen were not present to accept the electrons, the entire process would become backed up, halting ATP production and cellular respiration.

The incorrect choices misrepresent the function of oxygen in this context. Oxygen does not act as a donor of high-energy electrons, it does not play a role in raising mitochondrial temperature in a significant way, nor does it act as a catalyst in the ATP production reaction. Instead, its primary function is as the final electron acceptor, leading to the formation of water and ensuring the continuous flow of electrons through the electron transport chain. This is fundamental for ATP synthesis, which occurs through chemiosmosis,