Why is oxygen required for functioning of the etc?

Oxygen is essential for the functioning of the electron transport chain (ETC) because it serves as the final electron acceptor. As electrons are transferred through the chain, they release energy used to pump protons across the mitochondrial membrane, creating a proton gradient. Oxygen combines with these electrons and protons to form water, which helps maintain the flow of electrons. Without oxygen, the chain would become backed up, halting ATP production and cellular respiration.