Which of the following is the simplest amino acid?

Glycine and alanine are different with respect to one substituent on the $\alpha$-carbon. What are the other common substituent groups?

What is insulin?

Which is the correct option for sulphur-containing amino acids?

$A$: The polypeptide coil of collagen helix is strengthened by the establishment of hydrogen bonds between the $>NH$ group of the glycine residue of each strand and the $-CO$ group of the other two strands.
$R$: In the collagen helix,a locking effect also occurs with the help of proline and hydroxyproline amino acids.

The primary structure of a protein is determined by which of the following?