Zwitterion Definition:

A net neutral compound that exhibits charge separation. Amino acids exist as zwitterions at physiological pH.

Zwitterion Explained:

A zwitterion, usually used in context of proteins, is a molecule that contains two functional groups, each possessing opposite charges. Meaning that one contains a positive charge while the other contains a negative charge, and thus cancelling one another. Because the charges cancel each other, the molecule is said to be neutral, and this occurs at the isoelectric point.