So, let's get a red marker and a black marker. Okay, so for those NADH molecules produced in the matrix of the mitochondria V, the citric acid cycle, these NADH molecules are oxidized back into NAD plus along complex one of the electron transport chain. And when these two electrons travel through complex one and ultimately end up on Ubiquinone, a net result of four protons are pumped into the intermembrane space of the mitochondria. So when these electrons travel through complex one, this pumps four protons. Now, these two electrons are collected by Ubiquinol. That becomes ubiquinol.