Amino acids are

Out of the following,which is the best category to describe proteins?

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:

Differentiate between globular and fibrous proteins.

Peptide linkage is present in:

Which one of the nitrogen atoms of histidine is protonated first?