Question

A proton gradient across the mitochondrial inner membrane is a requisite for the synthesis of ATP. What contributes to the creation of this proton gradient?

Answer 1

Within the matrix, the electron carriers from Kreb's cycle undergo a reduction reaction and release their protons (ie NADH -> NAD- + H+). Then the protons are released into the intermembrane using the proton gradient. This active transport gradient is needed because the protons are flowing against their concentration.

Then the lone H+ in the intermembrane space go back into the matrix using ATP synthase. These protons contribute in ATP synthesis
ADP + Pi -> ATP