ATP synthase
ATP synthase is an enzyme that creates the energy storage molecule adenosine triphosphate (ATP). ATP is the most commonly used "energy currency" of cells for all organisms. It is formed from adenosine diphosphate (ADP) and inorganic phosphate (Pi). The overall reaction catalyzed by ATP synthase is:

ADP + Pi + 3H+out ⇌ ATP + H2O + 3H+inThe formation of ATP from ADP and Pi is energetically unfavorable and would normally proceed in the reverse direction.