Which of the following amino acids is $NOT$ synthesized in our body?

Consider the following statements:
Statement-$I$: The primary structure of a protein represents its amino acid sequence.
Statement-$II$: The $\alpha$-helix and $\beta$-pleated sheet structures of a protein represent its tertiary structure.

What is the correct order of acidity for the positions $(X)$,$(Y)$,and $(Z)$ in the given compound?

Column-$I$	Column-$II$
$A$. Tyrosine	$P$. Essential amino acid
$B$. Serine	$Q$. Ceric Ammonium Nitrate
$C$. Tryptophan	$R$. Neutral $FeCl_{3}$
$D$. Proline	$S$. Carbylamine Test - Negative

Select the correct set of answer :

The correct structure of the dipeptide gly-ala is

What type of compound the Legumelin is?