電子伝達鎖

The electron transport chain or ETC is the final stage of cellular respiration, where NADH and FADH₂ begin a series of redox reactions.

At complex I, NADH donates two electrons across different electron acceptors, reducing Q to QH₂.

At complex II, FADH₂ transfers electrons via Fe-S to a Q-molecule, forming another QH₂.

The QH₂ generated in these reactions then diffuse to complex III and transfer electrons to cytochrome c via a series of reactions called the Q cycle.

The reduced cytochrome c moves to complex IV, where after a series of electron transfers, oxygen accepts electrons and combines with protons to produce water.

As electrons pass through complexes I, III, and IV, the energy released is used to pump protons into the intermembrane space.

The pumped protons can then flow down their concentration gradient and activate complex V or ATP synthase to produce ATP from ADP and inorganic phosphate.

Overall, the ETC produces 32 ATP molecules from one molecule of glucose, making it the major energy contributing stage of cellular respiration.