Which of the following is the correct structure of tyrosine?

The number of disulphide linkages present in insulin are

$A$ short peptide on complete hydrolysis produces $3$ moles of glycine $(G)$,$2$ moles of leucine $(L)$ and $2$ moles of valine $(V)$ per mole of peptide. The number of peptide linkages in it are $..............$.

Which of the following is not an amino acid?

The prosthetic group of haemoglobin is

An example of a sulphur-containing amino acid is: