The electron transport chain consists of protein complexes embedded in the inner mitochondrial membrane, where it generates a proton gradient by a series of oxidation‑reduction, or redox, reactions. although all of the stages of cellular respiration (glycolysis, the citric acid cycle, and the electron transport chain) are necessary for life, the electron transport chain is sometimes called the most important stage.
first complete the sentence, then answer the question.
the electron transport chain uses the transfer of protein complexes to set up a proton gradient.

what is the function of the proton gradient in mitochodrion?
a. it is a potential energy that oxidizes o2, forming h2o
b. it is a potential energy that can power atp synthesis
c. it is a kinetic energy that interconverts nad+ and nadh
d. it is a chemical energy that directly drives the synthesis of protiens