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Question #45408
The Question
A mammalian population migrates to a high-latitude, sub-zero habitat. Over evolutionary time, it develops shorter extremities to minimize heat loss and exhibits a permanently elevated Basal Metabolic Rate (BMR). At the cellular level, this sustained thermoregulatory adaptation is most likely mediated by:
Options
- A.
Increased density of membrane-bound receptors for iodothyronines, leading to rapid generation of second messengers like cAMP.
- B.
Upregulation of intracellular receptors for iodothyronines, leading to enhanced gene expression and synthesis of metabolic enzymes.
- C.
Increased binding of peptide hormones to intracellular receptors, directly altering the permeability of the mitochondrial membrane.
- D.
Downregulation of nuclear receptors for thyroxine to prevent the negative feedback loop on the hypothalamus.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Evolutionary_Exception
Tackle problems where standard rules evolve or change based on specific environmental constraints.
Concepts Behind This Question
Thyroxine|Membrane_Receptors|Metabolic_Rate
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: The trap relies on confusing hormone receptor locations.
Because thermoregulation in extreme cold requires a strong, continuous metabolic response, students might incorrectly assume thyroid hormones use membrane-bound receptors for a 'rapid' second-messenger response (Option A).
However, NCERT strictly classifies iodothyronines alongside steroid hormones as utilizing intracellular receptors to mediate long-term genomic effects (Option B).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Chemical Coordination and Integration - Class 11 |
| Concept | Hormone Receptors Location |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |