Which description best characterizes a peptide bond?

• A. Peptide bond
• B. Glycosidic bond
• C. Phosphodiester bond
• D. Hydrogen bond

Answer: (A)

A peptide bond is a covalent amide linkage that joins the carboxyl group of one amino acid to the amino group of the next amino acid in a polypeptide. It forms by a dehydration synthesis reaction, releasing water. Because of resonance, this bond has partial double-bond character, making it planar and limiting rotation around the bond. This covalent linkage is what holds the amino acid sequence together in proteins, unlike the other bonds listed: glycosidic bonds connect sugars, phosphodiester bonds connect nucleotides in nucleic acids, and hydrogen bonds are non-covalent interactions that help stabilize structures but do not form the main backbone between amino acids.