How many amino acids are present in insulin?

The correct structure of the dipeptide gly-ala is

Describe the term $D$ and $L$ configuration used for the amino acids with examples.

Assertion $(A)$: In aqueous solution,amino acids exist in dipolar ion form.
Reason $(R)$: Most of the naturally occurring amino acids have $L$-configuration.
The correct option among the following is:

Stability of $\alpha$-Helix structure of proteins depends upon:

Leucine amino acid is: