How many amino acids are present in insulin?

Insulin is

Which of the following amino acids contains an imidazole ring?

Which functional group participates in disulphide bond formation in proteins?

What is the $pH$ of $0.01 \ M$ glycine solution? For glycine,$K_{a1} = 4.5 \times 10^{-3}$ and $K_{a2} = 1.7 \times 10^{-10}$ at $298 \ K$.

The $pH$ at the isoelectric point of three amino acids are given as follows:

Amino acid	$pH$ at Isoelectric point
$(Amino \ acid)_{I}$	$6$
$(Amino \ acid)_{II}$	$9.8$
$(Amino \ acid)_{III}$	$3.9$

$(Amino \ acid)_{II}$ is . . . . . . ?