Which of the following amino acids contains sulphur?

Polypeptide chains present in insulin are linked together by:

What are the number and types of polypeptide chains in human hemoglobin, respectively?

Statement $P$: The quaternary structure of proteins is either globular or fibrous.
Statement $Q$: The three-dimensional arrangement of molecules consisting of a single polypeptide chain is the quaternary structure of proteins.

Which of the following proteins is insoluble in any solvent?

$S$ - Statement: The amino acid with a non-polar $R$ group is serine.
$R$ - Reason: The amino acid with a polar and uncharged $R$ group is threonine.