What membrane is permeable to protons.?

The inner mitochondrial membrane is permeable to protons, specifically during the process of oxidative phosphorylation. This membrane contains protein complexes that facilitate the electron transport chain and the subsequent movement of protons (H⁺ ions) from the mitochondrial matrix to the intermembrane space, creating a proton gradient. This gradient is essential for ATP synthesis, as protons flow back into the matrix through ATP synthase, driving the conversion of ADP and inorganic phosphate into ATP.