| Peptide | $R _1$ | $R _2$ |
| $I$ | $H$ | $H$ |
| $II$ | $H$ | $CH _3$ |
| $III$ | $CH _2 COOH$ | $H$ |
| $IV$ | $CH _2 CONH _2$ | $( CH _2)_4 NH _2$ |
| $V$ | $CH _2 CONH _2$ | $CH _2 CONH _2$ |
| $VI$ | $( CH _2)_4 NH _2$ | $( CH _2)_4 NH _2$ |
| $VII$ | $CH _2 COOH$ | $CH _2 CONH _2$ |
| $VIII$ | $CH _2 OH$ | $( CH _2)_4 NH _2$ |
| $IX$ | $( CH _2)_4 NH _2$ | $CH _3$ |

$\begin{array}{|c|c|c|c|}\hline {} &\text { Molisch's Test} & {\text { Barfoed Test}} & {\text { Biuret Test}} \\ \hline \text { A} & { Positive } & {\text { Negative }} & {\text { Negative }} \\ \hline \text { B } & {\text { Positive }} & {\text { Positive }} & {\text { Negative }} \\ \hline \text { C } & {\text { Negative }} & {\text { Negative }} & {\text { Positive }} \\ \hline\end{array}$
$A, B$ and $C$ are respectively
$\begin{matrix}
\underset{X}{\mathop{H}}{{O}_{2}}C-C{{H}_{2}}-CH-C{{O}_{2}}\underset{Z}{\mathop{H}}\, \\
\,\,\,\,\,\,\,\,\,\,\,| \\
\,\,\,\,\,\,\,\,\,\,\,\,\,+N{{H}_{3}} \\
\end{matrix}$
The isoelectric point for the amino acid is