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. So metabolites such as pyruvate molecules or ATP molecules or citrate molecules actually depend on special protein transporters to move across the two sides of the membrane. Now, if we examine, if we take a small section of this region here, this is what we're going to get. So this is the outer and the inner membrane.