Lysine $H_2N-(CH_2)_4-CH(NH_2)-COOH$ is:

Which of the following gives a positive test with ninhydrin?

The number of possible tripeptides formed involving alanine $(ala)$,glycine $(gly)$,and valine $(val)$,where no amino acid has been used more than once is:

The dipeptide given below is used as:

The melting points and solubility in water of amino acids are generally higher than that of the corresponding halo acids. Explain.

$A$ dipeptide,$X$ on complete hydrolysis gives $Y$ and $Z$. $Y$ on treatment with aqueous $HNO_2$ produces lactic acid. On the other hand,$Z$ on heating gives the following cyclic molecule.
Based on the information given,the dipeptide $X$ is: