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. To actually generate those ATP molecules, and recall from the previous discussion, four protons are needed to actually generate a single ATP molecule. And so we see that we have a total of ten H plus ions pumped into the intermembrane space by this NADH produced in a citric acid cycle. We need four H plus ions to generate a single ATP molecule.