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Question #44537
The Question
A biochemist is investigating the osmotic pressure () of a tetrameric protein solution at . In its native folded state, the protein behaves as an ideal solute with a molar mass . Upon the addition of a chemical denaturant, the protein completely dissociates into four identical unfolded monomeric chains. The osmotic pressure is measured against a dialysate containing the exact same concentration of denaturant, ensuring only the protein contributes to the measured .
Due to the massive increase in the hydrodynamic radius and excluded volume upon unfolding, the denatured monomers exhibit non-ideal behavior. The osmotic pressure of such macromolecular solutions follows the virial expansion: where is the protein concentration in , is the molar mass of the kinetic solute particle, and is the second virial coefficient. For the denatured state, .
Calculate the ratio of the osmotic pressure of the denatured state to the native state () at a protein concentration of .
Options
- A.
4
- B.
36
- C.
37
- D.
40
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
Osmotic Pressure vs Diffusion|Protein Denaturation Specificity
Why This Question Is Tricky
Common Mistakes
This problem tests the limitations of van't Hoff's ideal osmotic pressure law () when applied to macromolecules.
Students often fall into two traps: (1) They account for the dissociation into 4 monomers but ignore the non-ideal excluded volume caused by unfolding (yielding a ratio of 4, Option A). (2) They account for the virial coefficient but forget that denaturation also cleaves the tetramer into monomers, incorrectly using the native molar mass in the denatured calculation (yielding a ratio of 37, Option C).
The true physical chemistry of protein denaturation requires accounting for both the change in the kinetic unit's molar mass and the massive increase in the hydrodynamic radius (Flory-Huggins theory / Virial expansion).
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Solutions - Class 12 |
| Concept | Osmotic Pressure vs Diffusion |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |