The building blocks of proteins are which of the following?

• A. Sugars
• B. Nucleotides
• C. Amino Acids
• D. Bases

Answer: (C)

Proteins are built from amino acids, the monomers that link together through peptide bonds to form long polypeptide chains. The sequence and properties of these amino acids—especially their side chains—drive how the chain folds into its three-dimensional shape, which in turn determines the protein’s function in the cell. There are about twenty standard amino acids used to build proteins, and their order along the chain dictates structure and activity.

Sugars are the monomers of carbohydrates, forming things like starch and cellulose. Nucleotides are the monomers of nucleic acids (DNA and RNA), and bases are the nitrogenous components of those nucleotides. None of these are the building blocks of proteins.