Coagulation of egg, on heating is because of :

Coagulation of egg on heating is a common example discussed in the context of protein chemistry.

Key concept: Proteins have four levels of structure — primary (peptide bonds), secondary (hydrogen bonds forming alpha-helix, beta-sheets), tertiary (3D folding), and quaternary. When a protein is heated, the secondary, tertiary, and quaternary structures are disrupted, but the primary structure (peptide bonds) remains intact. This process is called denaturation.

When an egg is heated:

1. The proteins (mainly albumin) in the egg white undergo denaturation.

2. The hydrogen bonds, disulfide bonds, and hydrophobic interactions maintaining the native protein structure are broken.

3. The protein unfolds and aggregates, causing the egg white to become opaque and solid (coagulation).

4. The peptide bonds in the primary structure are NOT broken during this process.

The biological activity of the protein is lost upon denaturation.

The correct answer is Option (2): Denaturation of protein occurs.