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. So we can summarize these four steps in the following four. So one, two, three and four. In one, those high energy electrons are extracted from these high energy electron carrier molecules synthesized in the citric acid cycle and glycolysis.