Which of the following gives the main forces that stabilise the tertiary structure of proteins?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Hydrogen bonds, disulphide linkages, van der Waals forces and electrostatic forces of attraction
The tertiary structure of a protein is the further folding of its secondary structure (α-helix or β-pleated sheet). The 2° and 3° structures are held by four main forces: hydrogen bonds, disulphide linkages (\( \ce{-S-S-} \) bonds between two cysteine units), van der Waals forces and electrostatic attraction between oppositely charged side chains. Only Option (1) names all four.
Why the other options are incorrect
Option (2) Electrostatic, hydrogen bonds and van der Waals forces — Incorrect. These three forces do act, but the list leaves out disulphide linkages. These covalent cross-links are among the strongest bonds holding the folded chain, so the list is incomplete.
Option (3) Electrostatic forces only — Incorrect. Electrostatic attraction between charged side chains is only one of the four forces. Without hydrogen bonds, disulphide linkages and van der Waals forces, the chain could not keep its folded shape.
Option (4) Electrostatic as well as hydrogen bonds — Incorrect. This list misses disulphide linkages and van der Waals forces, two of the four forces that stabilise the 2° and 3° structures.
NCERT (2026-27 edition):
Structure of Proteins – “(iii) Tertiary structure of proteins: The tertiary structure of proteins represents overall folding of the polypeptide chains i.e., further folding of the secondary structure. … The main forces which stabilise the 2° and 3° structures of proteins are hydrogen bonds, disulphide linkages, van der Waals and electrostatic forces of attraction.”