If the Side Chains of Amino Acids Contain Carboxyl (-COOH)

Question

If the side chains of amino acids contain carboxyl (-COOH) groups, they
A)contribute a positive charge to the amino acid at pH 10.
B)contribute a negative charge to the amino acid at pH 10.
C)have no effect on the charge of the amino acid at pH 10.
D)are considered acidic amino acids.
E)contribute a negative charge to the amino acid at pH 10 AND are considered acidic amino acids.

Accepted Answer

Carboxyl (-COOH) groups are acidic functional groups and will ionize in water to release a proton (H+), resulting in a negatively charged carboxylate (-COO-) group. At pH 10, which is basic, the carboxylate group will be fully deprotonated and contribute a negative charge to the amino acid. Therefore, any amino acid with a carboxyl side chain will be considered an acidic amino acid and will contribute a negative charge at pH 10.