What is the full name of the chemical group represented by $NH_{2}$?

What causes proteins to acquire a charge?

What is the smallest structural unit (monomer) of a protein called?

Assertion : The amino acid glycine comes under the category of nonessential amino acids.
Reason : This is due to the fact that it can not be synthesised in the body.

Select the correct option for the following matches:

$(1)$ Contractile protein	$(a)$ Immunoglobulin
$(2)$ Protein produced by cells	$(b)$ Globular protein
$(3)$ Protein that gives color to the iris	$(c)$ Actin
$(4)$ Protein for muscular movement	$(d)$ Melanin

For growth and repair in the body,$.......$ are required.