What is the net charge of amino acids at physiological pH?

At physiological pH, which is typically around 7.4, amino acids exist predominantly in their zwitterionic form. In this state, the amino group (-NH3⁺) is protonated and carries a positive charge, while the carboxyl group (-COO⁻) is deprotonated and carries a negative charge. The two charges typically balance each other out, resulting in no net charge for the amino acid as a whole.

This zwitterionic form is a key characteristic of amino acids, allowing them to be solubilized in physiological conditions and participate in various biochemical reactions without contributing to an overall charge. The specific behavior can vary based on the side chain of individual amino acids, but at physiological pH, the overall effect leads to a neutral net charge.

The variation in the side chain might alter charge characteristics in different environments or pH levels; however, under normal physiological conditions, amino acids maintain a zwitterionic state, resulting in no net charge overall.