And the better that acid is, the more likely that it will donate that H plus ion. And likewise the smaller our Ka is, the larger the PKA is and the less likely our acid will actually donate that H plus ion. So a smaller PKA means the acid is strong and it will be very likely to donate that H plus ion. So that is what we mean by the PKA. The PKA basically used to describe the strength of that acid. Now what are the acids that exist within our DNA?