# DBT JRF 2020 — Question 6

Exam: DBT JRF 2020 · Section: A · Topic: Biochemistry · Difficulty: Easy

## Question

The egg white protein, ovalbumin, is denatured in a hard-boiled egg. Which of the following is least affected?

## Options

- **A.** tertiary structure of ovalbumin
- **B.** quaternary structure of ovalbumin
- **C.** secondary structure of ovalbumin
- **D.** primary structure of ovalbumin

## Answer

Option D

## Explanation

Protein denaturation is the unfolding of a protein's three-dimensional structure due to disruption of non-covalent stabilising forces: hydrogen bonds (2° structure), hydrophobic interactions (3° structure), and electrostatic/van der Waals interactions (3° and 4° structure). The PRIMARY structure — the linear sequence of amino acids connected by peptide bonds (covalent amide bonds, bond energy ~350 kJ/mol) — is NOT broken by heat denaturation. Reversal of denaturation (renaturation) restores 3D structure because the primary structure is intact. Boiling an egg denatures ovalbumin irreversibly due to aggregation, but the polypeptide chain remains intact.

Source: https://mypyqbuddy.com/questions/the-egg-white-protein-ovalbumin-is-denatured-in-6a05a8a02adafec4702931ec