Question

Which structure of protein remains intact after coagulation of egg white on boiling?

• A. Primary
• B. Secondary
• C. Tertiary
• D. Quaternary

Answer 1

The Correct Option is A

Proteins possess multiple levels of structural organization: primary, secondary, tertiary, and quaternary. The coagulation of egg white when boiled involves physical and chemical changes that affect these structures.

1. Primary Structure: This is the linear sequence of amino acids linked by peptide bonds. Boiling does not break these covalent peptide bonds, thus preserving the primary structure.

2. Secondary Structure: This describes the folding of the polypeptide chain into alpha-helices and beta-sheets, stabilized by hydrogen bonds. Heat from boiling can break these hydrogen bonds, altering the secondary structure.

3. Tertiary Structure: This represents the protein's overall three-dimensional shape. Intramolecular bonds (hydrogen, ionic, and disulfide) that maintain the tertiary structure can be disrupted by heat.

4. Quaternary Structure: This applies to proteins composed of multiple polypeptide chains. The interactions between these chains, similar to tertiary structures, are susceptible to heat-induced disruption.

During boiling, egg white proteins undergo denaturation, characterized by the disruption of secondary, tertiary, and quaternary structures. The primary structure, defined by the sequence of amino acids connected by covalent peptide bonds, remains intact.

The intact structure is the Primary structure.

Consequently, boiling egg white denatures proteins by affecting non-covalent and disulfide bonds, which are crucial for higher structural levels. Only the primary structure of the proteins remains unaltered.