Question

At the isoelectric point for an amino acid, the species present are:

• A. $R-\underset{N{H}_2}{\underset{|}{CH}}-COOH$
• B. $R-\underset{{}^{+}N{H}_3}{\underset{|}{CH}}-COOH$
• C. $R-\underset{N{H}_2}{\underset{|}{CH}}-CO{O}^{-}$
• D. $R-\underset{{}^{+}N{H}_3}{\underset{|}{CH}}-CO{O}^{-}$

Answer 1

The correct option is D $R-\underset{{}^{+}N{H}_3}{\underset{|}{CH}}-CO{O}^{-}$

At the isoelectric point, amino acids are present in Zwitter ionic form.
$R-\underset{{}^{+}N{H}_3}{\underset{|}{CH}}-CO{O}^{-}$