What is the monomer unit for proteins?

• A. Nucleotides
• B. Monosaccharides
• C. Fatty acids
• D. Amino acids

Answer: (D)

Proteins are polymers built from amino acids, which serve as their basic building blocks. Each amino acid has an amino group, a carboxyl group, a hydrogen, and a distinctive side chain attached to a central carbon. During protein synthesis, amino acids link through peptide bonds in a dehydration reaction, forming a polypeptide chain that folds into a functional protein. The sequence of amino acids and their chemical properties determine the protein’s structure and function. The other molecules listed correspond to monomers of other biomolecules: nucleotides for nucleic acids, monosaccharides for carbohydrates, and fatty acids (along with glycerol) for lipids. So the monomer unit for proteins is amino acids.