Solution:
A basic amino acid which is a constituent of most proteins. It is an essential nutrient in the diet of vertebrates.
Proteins: the macromolecule and the monomer: Proteins are about 50% of the dry weight of most cells, and are the most complex of the macromolecules we will talk about, because there are 20 different monomers or building blocks, called amino acids.
Thus this is the required answer.