Answer:
The electron transport chain uses the transfer of ELECTRONS between protein complexes to set up a proton gradient
The function of the proton gradient in mitochodrion it's to provide potential energy that can power ATP synthesis
The answer is B.
Explanation:
Electron transport chains transfer electrons from an electron donor to an electron acceptor. The transfer of electrons aids translocation of protons across a membrane to form proton gradient that produce useful work.
The proton gradient can generate a chemiosmotic potential/proton motive force which supplies potential energy for ATP synthesis through oxidative phosphorylation.