Question

Proton permeability of outer membrane of mitochondria

Answer 1

During electron transport from NADH to O2, protons translocate from the matrix to the intermembrane space; since the outer membrane is freely permeable to protons, the pH of the outside medium is lowered briefly. The measured change in pH indicates that 10 protons are transported out of the matrix for every electron pair transferred from NADH to O2.