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Question #46845
The Question
The mantle epithelium of molluscs (responsible for shell biomineralization) and the vertebrate intestinal mucosa both require strict cellular polarity for unidirectional active transport. If a marine mollusc is subjected to severe osmotic stress, it must isolate its mantle cavity to prevent internal homeostasis failure. Which intercellular junction is primarily responsible for maintaining this epithelial polarity and preventing paracellular ion leakage, and what would be the consequence of its disruption?
Options
- A.
Gap junctions; failure to synchronize ciliary beating, leading to a collapse of the respiratory water current over the gills.
- B.
Tight junctions; inability to maintain an osmotic gradient for shell deposition due to the lateral diffusion of ion pumps and paracellular leakage.
- C.
Adhering junctions; detachment of the mantle epithelium from the underlying visceral mass, halting biomineralization.
- D.
Desmosomes; failure of active transport due to the inability to anchor Na+/K+ ATPases to the basal lamina.
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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
Epithelial Junctions Polarity|Mollusca Mantle Cavity|Tight_Junctions
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Functional Overlap Trap.
Students frequently confuse the specific roles of epithelial junctions.
While adhering junctions 'cement' cells together, they do not create a waterproof seal.
The critical realization is that Tight Junctions serve a dual role: acting as a paracellular barrier (stopping leakage) and an intramembrane fence (maintaining polarity by restricting protein diffusion), which is vital for the evolutionary adaptation of the molluscan mantle cavity.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Structural Organisation in Animals - Class 11 |
| Concept | Epithelial Junctions Polarity |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |