Which amino acid is achiral?

Optically inactive amino acid is :-

The list given below contains essential amino acids that are basic $(X)$ and also non-essential amino acids that are neutral $(Y)$. Identify $X$ and $Y$ from the following list:
$a)$ Lysine
$b)$ Alanine
$c)$ Serine
$d)$ Arginine
$e)$ Tyrosine

Proteins contain which of the following elements?

What is the effect of denaturation on the structure of proteins?

Which type of biomolecules have some structural similarity with synthetic polyamides? What is this similarity?