The structure of protein that is unaffected by heating is

Solution

Chemistry ma’am · 3 steps

Heat shakes loose the weak bonds that fold a protein, but it cannot break the peptide chain itself.

1. What heat does. Heating a protein denatures it. The extra energy breaks the weak attractions that hold the chain in its folded shape, and the protein loses its biological activity.

   Level	What holds it	On heating
   Primary	covalent peptide bonds (-CO-NH⁻) in the amino acid sequence	stays intact
   Secondary	hydrogen bonds in the α-helix and β-pleated sheet	destroyed
   Tertiary	hydrogen bonds, disulphide links, van der Waals and electrostatic forces	destroyed
   Quaternary	weak forces between separate polypeptide subunits	destroyed

2. Why primary survives. Peptide bonds are strong covalent bonds. Ordinary heating does not supply enough energy to break them, so the sequence of amino acids is unchanged. Boiling an egg is the everyday example: the albumin coagulates, but its chains stay whole.
3. So. Only the primary structure is unaffected by heating, so the answer is (c).

The idea to keep. Denaturation, whether by heat or by a change in pH, breaks only the weak forces that fold a protein. The covalent peptide bonds of the primary structure stay intact.

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