Part A - The role of O2 in electron transport In mitochondrial electron transport, what is the direct role of O2?

(A) to provide the driving force for the production of a proton gradient
(B) to function as the final electron acceptor in the electron transport chain
(C) to oxidize NADH and FADH2 from glycolysis, acetyl CoA formation, and the citric acid cycle
(D) to provide the driving force for the synthesis of ATP from ADP and Pi

Oxidative phosphorylation is a process that takes place in cellular respiration. It consists of two component pathways which includes the electron transport chain (etc) and chemiosmosis.

In etc the electrons are passed from one to another molecule, the energy is released by the electrochemical gradient.

In chemiosmosis, the energy stored in the electrochemical gradient is used to produce energy molecules in the form of ATP (Adenosine triphosphate).

The oxygen is present at the end of the etc. It's function is to accept the electrons also picks up the protons to form water. If oxygen is absent then no molecule will accept the electrons, the electron transport chain will stop. There will be no chemiosmosis as the ATP will not be produced in the absence of formation of a electron gradient.