So the electron transport chain is a series of proteins that receive these high energy electrons from NADH molecules and Fadh two molecules and they move these electrons along the inner membrane of the mitochondria. And the final acceptor of these electrons is oxygen. So we reduce oxygen to form the H 20 molecules. Now, we know from physics that as these electrons flow, they create an electrical current and that basically allows us to carry out some type of process to do work. And so we are able to actually pump these protons to establish a proton gradient. And that proton is gradient is then used by ATP synthase to actually generate those ATP molecules.