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

Solution

Chemistry ma’am · 3 steps

Boiling breaks the weak bonds that fold a protein, but the strong peptide bonds of the chain survive.

1. What boiling does. Heating egg white denatures the protein albumin. The chain unfolds, loses its shape and clumps together, which is why the white turns solid.
2. Which bonds break. Denaturation breaks only the weak forces: hydrogen bonds, ionic attractions, hydrophobic interactions and sometimes disulfide links. Covalent peptide bonds need much harsher conditions, such as acid hydrolysis, to break.

   Level	Held by	After boiling
   Primary	peptide bonds (covalent)	intact
   Secondary	hydrogen bonds (α-helix, β-sheet)	lost
   Tertiary	H-bonds, ionic, hydrophobic, disulfide	lost
   Quaternary	weak forces between subunits	lost

3. So. The amino acid sequence does not change, so the primary structure remains intact. The answer is (b).

The idea to keep. Denaturation destroys shape, not sequence. Heat, acid or alcohol break the weak bonds of 2°, 3° and 4° structure; the peptide bonds of the primary structure stay.

Answer from the NTA final answer key. Solution by PrepWiser.