So we have a potassium ion, let's say, found on the outside of that cell membrane. And this is the phospholipid bilayer. And notice that it exists in this cage, in this salvation shell, in which we have all these hydrogen bonds shown in green. And so, because these bonds, these electric interactions, are so stabilizing, it doesn't actually want to leave and break these bonds, because if it dissolves inside the non polar region of that phospholipid biolare, it will not be able to form those same energetically favorable interactions. So charged ions or molecule, charged ions or molecules do not easily pass across the membrane because they do not want to lose those energetically favorable water interactions that exist in that water cage. And to basically describe what we mean, let's take a look at these two molecules.