And what that means is it contains an amino group. And at least one of these sugars in the repeating disaccharide unit is actually modified with some type of negatively charged group. For instance, a sulfate group or a carboxylate group. Now, to see exactly what we mean, let's take a look at the following four examples of glycosaminoglycans that we'll find inside our body. So one of these glycosaminoglycans we actually discussed previously, so that is Heparin. We said heparin is this glycosaminoglycan that is produced and released by immune cells we call mast cells.