Amino acids are the monomers that link to form proteins.
EXPLANATION:
Amino acids create a common structure and are linked to form proteins. Function of protein is based on the shape or its primary structure. This shape is in turn dependent on how the amino acids are lined up in sequence.
Also, it depends on the sequence of nucleotides in its gene. Thus, for a protein to function properly, its structure should be formed properly based on how the amino acids are sequenced.