ATP

The oxygen helps cells to release energy as ATP during aerobic respiration. The oxygen helps to increase the permeability of the mitochondrial membrane allowing pyruvate formed in glycolysis to enter the matrix of the mitochondrion. The reduced NAD also formed passes its electrons down an electron transport chain in a series of redox reactions from one carrier molecule to the next. In doing so it increases the permeability of channel protein the inner membrane to hydrogen ions, which then pass into the inter-membrane space. This lowers the pH and helps to generate an electrochemical gradient which activates ATPase to combine ADP and Pi to form ATP.