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Question #45216
The Question
A missense mutation in a gene coding for a vital metabolic enzyme replaces a central Alanine residue with Proline within a critical right-handed α-helical domain. This substitution leads to the complete loss of enzymatic activity. Which of the following best explains the structural basis for this destabilization?
Options
- A.
Proline lacks a free amide hydrogen in the peptide bond, preventing intra-chain hydrogen bonding and inducing a 'kink' in the α-helix.
- B.
Proline's highly electronegative side chain disrupts the electrostatic interactions between adjacent turns of the α-helix.
- C.
The cyclic structure of Proline promotes excessive inter-chain hydrogen bonding, spontaneously converting the α-helix into a β-pleated sheet.
- D.
Proline forms rigid covalent cross-links with adjacent amino acids, restricting the flexibility of the α-helical backbone.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Hydrogen_Bonds|Proline|Alpha_Helix|Collagen
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often memorize from NCERT that hydrogen bonds stabilize secondary structures, but fail to apply the structural anatomy of specific amino acids.
The trap lies in understanding WHY Proline is a universal 'helix breaker' (lack of an N-H hydrogen in the peptide bond), rather than just associating it with general 'rigidity' or 'hydrophobicity'.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Biomolecules - Class 11 |
| Concept | Secondary Protein Structure Stabilizers |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |