The helical structure of a protein is stabilized by:

A. Peptide bond

B. Dipeptide bond

C. Hydrogen bonds

D. Van Der Waals forces

The secondary structures of proteins include the α-helix (alpha helix) and the β-pleated sheet. Both structures are stabilized by hydrogen bonds, which form between the carbonyl group of one amino acid and the amide group of another.

• β-pleated sheets can form supercoiled structures where 2–3 helices coil together to create stability.
• The α-helix is the most common and most stable form of secondary structure.

In the alpha helix, the carbonyl oxygen atom of one amino acid points in one direction and forms a hydrogen bond with the amide hydrogen atom of another amino acid four residues away. These hydrogen bonds, usually represented by dashed lines, are the key stabilizing forces of the helical structure.

Final Answer

Thus, the correct answer to this question is Option C.