Concept #1: Amino Acid Zwitterions

Practice: Which shows the proper structure of Leu at physiological pH?

Concept #2: Determining Predominant Amino Acid Structures

Example #1: At pH 2, which is the predominant structure of Val?

Practice: Fill in the groups for the predominant structure of Ala at pH 13?

Practice: Fill in the appropriate groups for Asp at pH 4.3.

Practice: Draw the predominant structure of Arg at pH 6.5? (pK a1 = 9.04, pKa2 = 2.17, pKa3 = 12.48).

Practice: At what pH would an amino acid bear both a neutral -COOH and a -NH 2 group?