An electron transport chain (ETC) is a series of compounds that couples electron transfer with the transfer of protons across a membrane and transfer electrons from electron donors to electron acceptors with the help of redox reactions. This generates chemical energy in the form of adenosine triphosphate (ATP) by creating an electrochemical proton gradient, that drives ATP synthesis. The breakdown of proton gradient along the concentration gradient forms the ATP molecules.
F0 protein complex of ATP synthase forms the channel through which protons cross the inner membrane during. For each ATP produced, 2H+ passes through F0 from the intermembrane space to the matrix down the electrochemical proton gradient.