A peptide has pKa values of 2.0, 4.5, and 9.0. At pH 5.0, the net charge is -1. What does this indicate about the predominant form of the peptide?

• A. The peptide is predominantly in its protonated form.
• B. The peptide is neutral.
• C. The peptide is predominantly in its deprotonated form.
• D. The peptide is positively charged.

Answer: (C)