Answer
The structure of the major form of phenylalanine at pH values
of 1, 5.5, and 11 are shown in the picture below.
Work Step by Step
The general rule when determining if a group will be protonated is: at solution pH below the group's pKa value, the group will be protonated; at pH higher than the group's pKa value, it will not be protonated.
