What does ultimately happen to electrons and hydrogens carried by NADH and FADH2 to the electron transport system during aerobic respiration? A. They are used to reduce pyruvate and produce ethanol. B. They stay in the cell attached to carriers of the electron transport chain. C.They are converted into glucose molecule. D.They bind to oxygen and are expelled from the cell as water. E.They are pumped out of the cell by a proton pump..