Answer:
Proton motive force, compounds such as ATP.
Step-by-step explanation:
Large amount of proton motive force(PMF),the usable enegy for the cell ,are produced during electron transport chain when high energy compound such as ATP pump hydrogen ions against the concentration gradient.
When the protons are transported against their concentration gradient at that time proton motive force is generated.
PMF generates energy for the synthesis of ATP by the phosphorylation of ADP with inorganic phosphate.