But the inner membrane doesn't actually contain these mitochondrial porns. So that means it is impermeable to charged molecules and it's impermeable to polar molecules. So molecules such as citrate molecules or pyruvate molecules or ATP molecules actually depend on special protein membranes or membrane proteins to actually shuttle those molecules across the matrix, across the matrix and into the intermembrane space. So the outer membrane is permeable to the majority of small molecules and anions due to the presence of voltage gated channels we call mitochondrial porns or VDAC. It allows the movement of anionic metabolites, such as chloride molecules and ATP molecules and so forth. But the inner membrane lacks these mitochondrial porns, and so it's impermeable to ions and polar molecules.