What are the building blocks of proteins?

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

Answer: (A)

Proteins are built from amino acids. Each amino acid has an amino group, a carboxyl group, a central carbon, a hydrogen, and a distinctive side chain. When the carboxyl group of one amino acid reacts with the amino group of another, a peptide bond forms and a molecule of water is released, linking them into a polypeptide chain. The sequence of amino acids in this chain—the primary structure—dictates how the chain will fold into its three-dimensional shape, and that shape determines the protein’s function. There are about 20 standard amino acids used to make proteins, and their varied side chains give proteins their diverse properties. Nucleotides form nucleic acids, monosaccharides form carbohydrates, and fatty acids form lipids, so the building blocks specific to proteins are amino acids.