Which of the following can disrupt the native structure of a protein?

The correct answer is Option (4) → Both (1) and (2)

A native protein keeps its biological activity only while its three-dimensional structure is intact. Anything that disturbs the hydrogen bonds holding this structure causes denaturation.

Option (1) Change in temperature — Correct. A physical change; heating disturbs the hydrogen bonds, as in the coagulation of egg white on boiling.

Option (2) Change in pH — Correct. A chemical change that also disturbs the hydrogen bonds.

Option (3) Formation of disulphide linkages — Incorrect. Disulphide linkages are among the forces that stabilise the secondary and tertiary structures; they hold the native shape, they do not disrupt it.

NCERT (2026-27 edition):
10.2.4 Denaturation of Proteins – “Protein found in a biological system with a unique three-dimensional structure and biological activity is called a native protein. When a protein in its native form, is subjected to physical change like change in temperature or chemical change like change in pH, the hydrogen bonds are disturbed. Due to this, globules unfold and helix get uncoiled and protein loses its biological activity.”