Now, before we determine what the pi value of specific proteins is, let's ask the following question. How do you determine what the pi value is of a single amino acid? So let's take a look at the following four cases. 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.