The electron transport chain
THE ELECTRON TRANSPORT CHAIN · IMAT Doutor1 / 1
In an isolated mitochondrion supplied with substrate and oxygen but no ADP, electron transport slows almost to a stop. Adding ADP restores it immediately. What does this show?
A
ADP is a direct substrate of complex I, which cannot accept electrons from NADH unless ADP is bound to it first
B
Oxygen cannot be consumed in the absence of ADP, because complex IV uses ADP rather than oxygen as the final acceptor of the electrons that pass along the chain
C
ADP is required to keep the inner membrane intact, and without it the membrane leaks until the chain can no longer function
D
The chain runs backwards when there is no ADP, oxidising water and reducing NAD⁺, until ADP is supplied again
E
Electron transport is coupled to ATP synthesis: without ADP the gradient cannot be discharged, and the accumulated proton-motive force opposes further pumping
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