If the side chain group $-R$ for an amino acid is $-CH_{2}OH$,identify the amino acid from the following:

Which of the following amino acids is an essential amino acid?

Which of the following molecules has the ability to form a zwitterion?

In an amino acid,the carboxylic group ionises at $pH = 2.56$ $(pK_{a_1})$ and the ammonium ion ionises at $pH = 9.38$ $(pK_{a_2})$. The isoelectric point of the amino acid is at:

Sulphur $(S)$ containing amino acids from the following are:
$(a)$ isoleucine
$(b)$ cysteine
$(c)$ lysine
$(d)$ methionine
$(e)$ glutamic acid

The one that does not stabilize $2^{\circ}$ and $3^{\circ}$ structures of proteins is