Now and this leads us directly into property six. So recall from our discussion on non covalent interactions we said that for non covalent interactions to actually be strong enough and to actually be meaningful, the distance between our bonds, the distance between the molecules and atoms forming the bonds actually has to be short enough. And so what that means is in order for the substrate to actually get close to the active side, to get close enough to form those meaningful non covalent bonds, the shape of that substrate has to be complementary to that shape of the active side of the enzyme. And that leads us to property six active sites. Active sites. This should be active sites where is my marker?