Question

An amino acid under certain conditions has both positive and negative charges simultaneously in the same molecule. Such a form of amino acid is called

• A. Basic form
• B. Acidic form
• C. Aromatic form
• D. Zwitterionic form

Answer 1

The correct option is D Zwitterionic form

Zwitterion

A zwitterion is a compound that has a negative charge on one atom and a positive charge on a non-adjacent atom in the same molecule. Hence, the net charge on a zwitterion is zero. Hence, a zwitterion does not migrate towards any electrode in an electric field.
Amino acids also exist as zwitterion at a particular $pH$ value because of the presence of ionizable groups such as $N{H}_2$ and $COOH$.

Acidic amino acids

Acidic amino acids have two carboxylic groups $\left(COOH\right)$ and one amino group $\left(N{H}_2\right)$, so the number of $COOH>N{H}_2$ .
Examples include glutamic acid, aspartic acid.

Basic amino acids

Basic amino acids have two $N{H}_2$ groups and one $COOH$ group. So, the number of $NH2>COOH$.

Examples include lysine and arginine.

Aromatic amino acids

Aromatic amino acids possess a cyclic structure with a straight side chain bearing carboxyl and amino groups.

Examples include tyrosine and phenylalanine.

Final answer: d. Zwitterionic form