All amino acids have two ionizable functional groups: an -amino group (average p K2 of 9.4 ) and an -carboxylic acid group (average pKa of 2:2). Glutamic acid has an ionizable side chain (R group) with a p Ka of about 4.1. One of the possible ionization states of glutamic acid is shown in the image. At what pH would this structure of glutamic acid be the predominant ionization state? Consider the ionization state of all three of the functional groups. At what pH would this structure of glutamic acid be the predominant ionization state? Consider the ionization state of all three of the functional groups. The protonated form of the R group of glutamic acid is shown in the structure. The ratio of the protonated form to the charged (deprotonated) form depends on the pKn of the R group and the pH of the solution. Select the pH values at which the charged form of the R group would predominate. 7.0 2.5 4. 1 9.5