Zwitterion Definition

It comprises functional groups: an amino group (positive) and a carboxylate group (negative), alongside a side chain group (R group). Amino acid is in a zwitterionic state at a pH of 2.2 to 9.4, and therefore with a net zero charge.

However, when the pH is decreased below 2.2, the amino acid would have a net charge of +1 as the carboxylic group becomes neutral. When the pH is increased above 9.47, the amino acid would have a net charge of -1 as the amino group becomes neutral and the negative carboxylic group is predominant.