Question

What is the charge on phenylalanine at pH 11? [Examples: -1, 0, OR +1]

What is the charge on glycine at pH 3.1? [Examples: -1, 0, OR +1]

What is the charge on aspartic acid at pH 5? [Examples: -1, 0, OR +1]

Answer 1

At pH 11, the carboxyl and amino groups of phenylalanine are deprotonated (COO^- and NH₂) resulting in a charge of -1.

At pH 3.1, the carboxyl group of glycine is deprotonated (COO^-) whereas its amino group is still protonated (NH₃⁺) resulting in a charge of 0.

At pH 5, the carboxyl group of glycine is deprotonated (COO^-), its amino group is protonated (NH₃⁺), whereas its side group is deprotonated (COO^-) resulting in a charge of -1.