And what the electron transport chain does is it ultimately establishes a proton gradient. And what that means is the electron transport chain are these proteins that create an electric potential difference between the two sides of the membrane of the mitochondria, and that stores energy across the cell membrane. So proteins are important because they mediate energy storage, as well as act as enzymes, receptors and transporters. So number seven, which is what we mentioned earlier and just a moment ago, membranes are polar. And what that means is, compared to the outside of the cell, the inside of the cell basically differs in the charge. And because we have a separation of charge between the two sides of the membrane, from basic physics, we know that that creates establishes an electric potential difference, an electric dipole moment.