What type of macromolecule are amino acids and what bond links them in proteins?

• A. Nucleic acids; phosphodiester bonds
• B. Proteins; peptide bonds
• C. Carbohydrates; glycosidic bonds
• D. Lipids; ester bonds

Answer: (B)

Amino acids are the building blocks, or monomers, of proteins, which are the macromolecules formed when many amino acids link together. The connection between two amino acids is a peptide bond, created by a dehydration (condensation) reaction between the carboxyl group of one amino acid and the amino group of the next. This covalent bond links amino acids into a polypeptide chain that folds into a functional protein. The other macromolecule types use different linking bonds: nucleic acids are held together by phosphodiester bonds, carbohydrates by glycosidic bonds, and lipids by ester bonds.