And the final column describes the PKA value. Now, what is the PKA value? Well, if the PH of our solution, in which that molecule is in, is equal to the PKA value, then what that means is exactly 50% of the molecules will exist in the acid form, and the other 50% will exist in the conjugate base form. So if we're below a PH of the PKA, so let's say in this particular case, if we're below a PH of 3.1, then the acid form of the molecule will predominate. But if we're above a PH of 3.1, then what that means is this conjugate base form will predominate. And that's exactly why at a normal physiological PH of around seven, every single one of our amino acid contains an alpha called a carboxyl group that exists in the carboxylate ion form, because the PH of seven is above a PH of three is above the PH of 3.1.