Ubiquinol then travels through the core of the membrane and attaches onto complex three. And complex three then moves those electrons ultimately onto cytochrome C. In the process, a total of two, a net result of two protons, are actually pumped across the membrane from the matrix and into the intermembrane space. And finally, cytochrome C carries those electrons onto complex four. And in complex four, as those electrons travel through the complex and ultimately are used to reduce oxygen into water, we pump a net result of four ATP molecules from the matrix of the mitochondria into the intermembrane space. And so when a single NADH molecule produced in the citric acid cycle found in the matrix is oxidized into NAD plus by the electron transport chain, we transport a net result of four, two and two so ten protons into the intermembrane space. Now, these ten protons then move via complex five, also known as ATP synthase.