Question

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

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

Answer 1

The correct option is D Zwitterionic form

• In a neutral solution, an amino acid molecule exists as a dipolar ion (zwitter ion), i.e., a molecule containing positive and negative ionic groups.
• The charge on the amino acid changes with pH.
• In an acidic solution (low pH) the amino acid picks up $H^{+}$ ions and becomes positively charged.
• In alkaline solution (high pH) the amino acid donates $H^{+}$ ions to the medium and becomes negatively charged.
• The pH at which the amino acid is electrically neutral, and the molecule exists as a zwitterion is called the isoelectric pH.

So, the correct answer is 'Zwitterionic form'.