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Question #44972

Difficulty: 8/10 | 🟢 Free

The Question

An aqueous buffer solution at $298\text{ K}$ ( $\text{pH} = 7.4$ ) contains a folded globular protein and a G-C rich double-stranded DNA (dsDNA). A high concentration of urea ( $8\text{ M}$ ) is added to the solution. Which of the following statements correctly describes the primary structural changes and the underlying thermodynamic reasons?

Options

A.
Protein unfolds via disruption of the hydrophobic effect; dsDNA remains intact due to dominant base-stacking interactions.
B.
Both denature completely; urea outcompetes H-bonds in the protein and between nucleosides in the dsDNA.
C.
dsDNA denatures via H-bond disruption between nucleotides; the protein's hydrophobic core remains intact.
D.
Protein unfolds via hydrophobic effect disruption; dsDNA undergoes cleavage of phosphodiester bonds yielding nucleosides.

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Protein Denaturation Specificity|Base Pairing Stability|Nucleoside vs Nucleotide

Why This Question Is Tricky

Common Mistakes

The question tests the fundamental thermodynamic drivers of macromolecular stability and the specific action of chaotropic agents.

Students often mistakenly believe that hydrogen bonding is the primary stabilizing force for both proteins and DNA, and that urea denatures DNA as easily as proteins by outcompeting H-bonds.

The 'hidden variable' is that DNA stability is predominantly driven by base-stacking, making it resistant to $8\text{ M}$ urea at $298\text{ K}$ .

Additionally, it incorporates a structural nomenclature trap, testing the distinction between nucleosides (base + sugar) and nucleotides (base + sugar + phosphate) to eliminate distractors.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Biomolecules - Class 12
Concept	Protein Denaturation Specificity
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free