Which of the following reagents gives a blue colour with proteins?

When $HNO_3$ is dropped into the palm and washed with water,it turns yellow. The above yellow colour is due to:

The following tetrapeptide can be represented as:
($F, L, D, Y, I, Q, P$ are one-letter codes for amino acids)

Observe the structures of the following compounds:
$1$. $2$-chlorobutane
$2$. Glycine $(NH_2CH_2COOH)$
$3$. Alanine $(CH_3CH(NH_2)COOH)$
$4$. Styrene $(C_6H_5CH=CH_2)$
$5$. Menthol
The total number of structures/compounds which possess asymmetric carbon atoms is $....$

The prosthetic group of haemoglobin is

Insulin is a .........