There are four cases that we basically have to remember. So case number one, let's suppose that the amino acid is not ionizable. If that's the case, if the side chain is not ionizable, then to find the pi value of that particular amino acid, to find the isoelectric point, we simply sum up and we take the average of the PKA values of the terminal alpha amino group and the terminal carboxyl amino group and the terminal carboxyl group of that particular amino acid. Remember, every single amino acid contains an a terminal alpha carboxyl group and a terminal alpha amino group. And those two groups are also capable of losing and gaining h atoms at specific PH values. So if the side chain is non ionizable, then the isoelectric point of that amino acid is the average of the PKA values of the terminal alpha amino group and the terminal alpha carboxyl group.