Figure 2.11 A variety of conjugate acid–base pairs. Many conjugate acid–base pairs are important in biochemistry. A sampling of such pairs is shown. Notice that some acids can release more than one proton. The dissociation reaction and the pK_a for each pair are shown where they lie along a pH gradient. The equilibrium constants for the acids are given at the left of the illustration. *Note the pK_a of carbonic acid. Because of the large reservoir of carbon dioxide in the blood and its rapid equilibration with carbonic acid, the pK_a of carbonic acid in blood is taken to be 6.1.