How many disulfide bonds connect the $A$ and $B$ chains of human insulin to each other?

Which of the following groups in the structure of an amino acid is basic?

Give information on the structural organization of proteins. Mention their general functions.

Which bond connects two 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.

Which statement about protein is wrong?