What are linked by peptide bonds to form polypeptide chains?

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

Answer: (B)

Peptide bonds are the links that hold amino acids together to form polypeptide chains. This bond forms when the carboxyl group of one amino acid reacts with the amino group of the next amino acid, releasing a molecule of water in a dehydration synthesis. The resulting covalent bond, an amide linkage, stitches amino acids into a polymer with a repeating backbone. The order of amino acids creates the primary structure, which then folds into functional proteins.

Nucleotides, by contrast, are joined by phosphodiester bonds to form nucleic acids; monosaccharides join by glycosidic bonds to make polysaccharides; fatty acids and glycerol connect by ester bonds to form lipids.