Using a graph of pH versus concentration, how would you identify the zwitterionic form of an amino acid?

• A. Look for the pH where the concentration of the zwitterion is zero.
• B. Look for the pH where the concentration of the zwitterion is equal to the concentration of the protonated form.
• C. Look for the pH where the concentration of the zwitterion is lowest.
• D. Look for the pH where the concentration of the zwitterion is highest.

Answer: (D)