So we have 1234 of these carbon atoms, and each one of these carbon atom has two h atoms. Now, at the terminal end of the side group, we have a primary amino group. And what that means is we have a nitrogen that is bound to a single carbon, as shown in the following diagram. Now, all of these Lysine amino acids at the normal physiological PH of around seven have a full positive charge on that nitrogen. And that's because to actually deprotonate our nitrogen, we really have to increase our PH. We have to make it basic, because the PKA value of this nitrogen is ten.