Which bonds are primarily responsible for the peptide backbone linking amino acids in a polypeptide chain?

Which bonds are primarily responsible for the peptide backbone linking amino acids in a polypeptide chain?

• A. Hydrogen bonds
• B. Ionic bonds
• C. Covalent disulfide bonds
• D. Peptide (amide) bonds

Answer: (D)

The bonds that link amino acids in a polypeptide chain are peptide bonds, also called amide bonds. They form when the carboxyl group of one amino acid reacts with the amino group of the next amino acid in a dehydration synthesis reaction, releasing a molecule of water and creating a covalent link between the carbonyl carbon and the amide nitrogen. This covalent backbone holds the sequence of amino acids together to form the polypeptide. Hydrogen bonds, in contrast, are not the bonds that join the amino acids themselves; they form between backbone atoms to stabilize secondary structures like alpha helices and beta sheets. Covalent disulfide bonds can cross-link side chains (such as cysteines) and help stabilize tertiary or quaternary structure, but they do not form the main chain. Ionic bonds are electrostatic attractions between charged side chains and also influence folding, not the direct backbone linkage. So the peptide (amide) bonds are the fundamental covalent links that create the repeating backbone of a polypeptide.

The bonds that link amino acids in a polypeptide chain are peptide bonds, also called amide bonds. They form when the carboxyl group of one amino acid reacts with the amino group of the next amino acid in a dehydration synthesis reaction, releasing a molecule of water and creating a covalent link between the carbonyl carbon and the amide nitrogen. This covalent backbone holds the sequence of amino acids together to form the polypeptide.

Hydrogen bonds, in contrast, are not the bonds that join the amino acids themselves; they form between backbone atoms to stabilize secondary structures like alpha helices and beta sheets. Covalent disulfide bonds can cross-link side chains (such as cysteines) and help stabilize tertiary or quaternary structure, but they do not form the main chain. Ionic bonds are electrostatic attractions between charged side chains and also influence folding, not the direct backbone linkage. So the peptide (amide) bonds are the fundamental covalent links that create the repeating backbone of a polypeptide.