Where would glycine have a negative charge?

The correct answer is based on the behavior of glycine, which is the simplest amino acid, depending on the pH of its environment. In a basic environment, glycine will lose a proton from its carboxylic acid group, resulting in a negatively charged carboxylate anion (–COO^-). Additionally, the amino group will remain protonated and carry a positive charge (–NH3^+).

Thus, in a basic medium, glycine predominantly exists in a zwitterionic form where it has both a positive and a negative charge. The presence of the negative charge in this scenario is what makes this environment significant for understanding amino acid behavior and charge at varying pH levels.

In contrast, in a highly acidic environment, glycine would be fully protonated and carry a positive charge due to the protonation of both the amino and carboxyl groups. At neutral pH, glycine would typically exist in its zwitterionic form as well, but that does not emphasize the negative charge present. At high temperatures, the charges on amino acids do not change due to temperature alone; it does not intrinsically alter ionizability based on pH. Therefore, the answer correctly identifies the pH condition