What bond links amino acids together in proteins?

• A. Salt bond
• B. Disulfide bond
• C. Peptide bond
• D. Hydrogen bond

Answer: (C)

The bond linking amino acids in proteins is a peptide bond, a covalent amide bond that forms between the carboxyl group of one amino acid and the amino group of the next. This connection is created by dehydration synthesis, releasing a water molecule as the chain grows. The peptide bond has partial double-bond character from resonance, which makes the backbone planar and rigid and establishes the direction from the N-terminus to the C-terminus. Other bonds stabilize structure but don’t form the main chain: salt bonds are ionic interactions between charged side chains, disulfide bonds cross-link cysteine residues to add stability, and hydrogen bonds help shape secondary structures by connecting backbone atoms within the chain. In cells, peptide bonds are formed during protein synthesis by the ribosome as amino acids are added to the growing polypeptide.