Which forces stabilize alpha helices and beta pleated sheets?

Which forces stabilize alpha helices and beta pleated sheets?

• A. Hydrogen bonds
• B. Ionic bonds
• C. Covalent bonds
• D. Hydrophobic interactions

Answer: (A)

Hydrogen bonds between the peptide backbone are the key factor that stabilizes alpha helices and beta pleated sheets. In an alpha helix, each carbonyl oxygen forms a hydrogen bond with the amide hydrogen four residues ahead, creating a regular, repeating structure along the chain. In beta sheets, hydrogen bonds form between carbonyl and amide groups on adjacent strands, pairing strands in either a parallel or antiparallel arrangement to create a sheet-like fabric. While other interactions like ionic or covalent bonds and hydrophobic effects influence overall protein folding and stability, they do not establish the characteristic, repeating backbone hydrogen-bond pattern that defines these secondary structures.

Hydrogen bonds between the peptide backbone are the key factor that stabilizes alpha helices and beta pleated sheets. In an alpha helix, each carbonyl oxygen forms a hydrogen bond with the amide hydrogen four residues ahead, creating a regular, repeating structure along the chain. In beta sheets, hydrogen bonds form between carbonyl and amide groups on adjacent strands, pairing strands in either a parallel or antiparallel arrangement to create a sheet-like fabric. While other interactions like ionic or covalent bonds and hydrophobic effects influence overall protein folding and stability, they do not establish the characteristic, repeating backbone hydrogen-bond pattern that defines these secondary structures.