Which amino acid groups are involved in hemoglobin protonation?

• A. Carboxyl groups are involved in hemoglobin protonation.
• B. Free alpha amino groups are involved in hemoglobin protonation.
• C. Amino acid R groups are involved in hemoglobin protonation.
• D. Heme groups are involved in hemoglobin protonation.

Answer: (C)