Question

Which of the following bonds is responsible for maintaining the secondary structure of proteins?

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

Hint:

Remember: Primary structure = Covalent (Peptide) bonds; Secondary structure = Hydrogen bonds; Tertiary structure = Hydrophobic, Ionic, Disulfide, and van der Waals interactions.

Answer 1

The Correct Option is B

Step 1: Meaning of protein secondary structure. 
The secondary structure of a protein describes how the backbone of the polypeptide chain folds locally. It focuses only on the arrangement of the main-chain atoms and does not consider side chains or the overall folding of the protein.

The two most common secondary structures are the α-helix and the β-pleated sheet.

Step 2: Force responsible for stability.
These structures are held together mainly by hydrogen bonding. The hydrogen bonds form between:

• The carbonyl oxygen (\(C=O\)) of one peptide bond, and
• The amide hydrogen (\(N-H\)) of another peptide bond.

In an α-helix, this hydrogen bonding occurs between the \(n^{th}\) amino acid and the \((n+4)^{th}\) amino acid along the chain, creating a stable helical shape.

Other bonds play different roles:

• Peptide bonds determine the amino acid sequence (primary structure).
• Disulfide bonds help stabilize the folded 3D structure.
• Ionic bonds contribute mainly to tertiary and quaternary structures.

Step 3: Final conclusion.
Hydrogen bonds are the main interactions responsible for stabilizing the secondary structure of proteins.