Write the structural formula of $\mathrm{N}$-methyl acetamide. What is the name of the functional group in this compound?

Tryptophan and histidine have the structures $\left(\mathrm{I}\right)$ and $\left(\mathrm{II}\right)$ respectively. Classify them into neutral/acidic/basic $\propto$-amino acids and justify your answer. (Hint: Consider involvement of lone pair in resonance).

Compare the molecular masses of the following compounds and explain the observed melting points.

Formula	Molecular mass	Melting point
	$89$	${293.5}^{\mathrm{o}}\mathrm{C}$
${\mathrm{C}}_5{\mathrm{H}}_{11}-{\mathrm{NH}}_2$	$87$	$-{55}^{\mathrm{o}}\mathrm{C}$
${\mathrm{C}}_3{\mathrm{H}}_7-\mathrm{COOH}$	$88$	$-7.9^{\mathrm{o}}\mathrm{C}$

A protein chain has the following amino acids residues. Show and label the interactions that can be present in various pairs from these giving rise to tertiary level structure of protein.