Final answer:
The chemiosmotic mechanism generates about three ATP molecules per oxidized NADH and two ATP molecules per oxidized FADH2 during aerobic respiration.
Step-by-step explanation:
In the chemiosmotic mechanism of aerobic respiration, each pair of electrons transferred from NADH to oxygen via the electron-transport chain (ETC) releases sufficient energy to drive the formation of approximately three ATP molecules. This is achieved through oxidative phosphorylation, where the energy stored in the NADH is used to pump protons across the mitochondrial membrane, generating a proton motive force. The return flow of protons through ATP synthase harnesses this proton motive force to produce ATP from ADP and inorganic phosphate.
However, the electrons that are transferred from FADH2 to oxygen produce only about two ATP molecules, because FADH2 contributes its electrons to the ETC at a lower energy level compared to NADH. During the complete aerobic respiration of one glucose molecule, the maximum theoretical yield of ATP is 38 molecules, but this number can be lower in actual cellular conditions.