The structure of protein that remains intact after the coagulation of egg white on boiling is the Primary structure. The correct answer is Option B.

The primary structure of a protein is the sequence of amino acids that are linked by peptide bonds. This sequence dictates the protein's higher levels of structure including secondary, tertiary, and quaternary structures. Regardless of the change in the protein's conformation due to denaturation (such as what happens during boiling of egg white), the sequence of amino acids remains the same since the peptide bonds do not get broken under such conditions.

When egg white is boiled, the proteins denature, which means the structure of the protein becomes altered due to the breakdown of non-covalent interactions that hold the protein's higher-order structures together. This includes:

• Secondary structure: This involves hydrogen bonding within the peptide backbone, producing structures such as alpha-helices and beta-sheets.


• Tertiary structure: This involves the overall three-dimensional folding of the protein, driven by interactions such as hydrogen bonds, ionic bonds, hydrophobic interactions, and disulfide bridges.


• Quaternary structure: This involves the arrangement and interactions of multiple protein subunits in a multi-subunit complex.

During coagulation caused by heat, the weak hydrogen and ionic bonds of secondary and tertiary structures are broken and the proteins can aggregate or form gel-like structures, changing the consistency of the egg white. However, the covalent peptide bonds of the primary structure stay intact throughout this process.