question_answer 19)

  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:

                  (d) A zwitterion is a neutral molecule having both the cationic and anionic charges on thesame molecule. Amino acids are the best known examples of zwitterion. In acidic solution' amino group accepts a hydrogen ion to become positively charged. Whereas, in alkaline solution the carboxyl group donates a hydrogen ion to becomenegatively charged. The pH at which the amino acid is electrically neutral is calledisoelectric pH.