1 Answer | Add Yours
Amino acids exist as zwitterions when they are at their isoelectric point (also known as the pI value). This is the pH at which the amino acid has both a negative charge (on the carboxylate side of the molecule) and a positive charge (on the amino side of the molecule). Overall, it is a a neutral molecule, but it has both charges present within the structure. The charges are always +1 and -1.
This is only true for amino acids at that particular pH. When the pH changes, one of the ions goes away. At low pH values, there is an excess of H+ ions present resulting in the protonation of the negative ion so the amino acid has a positive charges. At high pH values, there is an excess of OH- ions present resulting in removal of the proton from the carboxylic acid side and as a result, we end up with a negative ion.
We’ve answered 315,905 questions. We can answer yours, too.Ask a question