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Question #47438
The Question
Cyclosporin A, produced by Trichoderma polysporum, is widely used as an immunosuppressive agent to prevent allograft rejection. It functions by inhibiting calcineurin, an intracellular calcium-dependent enzyme vital for T-cell activation. A parallel calcium-dependent mechanism governs synaptic delay and summation kinetics at chemical synapses. Which of the following statements regarding these calcium-mediated physiological processes is INCORRECT?
Options
- A.
In T-lymphocytes, the calcium-calcineurin pathway regulates gene transcription, whereas at the synaptic knob, calcium influx triggers synaptotagmin-mediated vesicle fusion.
- B.
Cyclosporin A induces immunosuppression by directly blocking the voltage-gated calcium channels on the T-cell membrane, preventing the initial calcium influx required for activation.
- C.
The temporal delay observed at a chemical synapse is primarily attributed to the kinetics of calcium channel opening and the subsequent calcium-dependent exocytosis.
- D.
Both the activation of cell-mediated immunity by T-cells and the release of neurotransmitters into the synaptic cleft are strictly dependent on a transient rise in cytosolic Ca2+ levels.
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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
Calcineurin|Interleukin-2|Synaptic vesicle kinetics
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students often confuse the 'inhibition of a calcium-dependent pathway' with the 'blockade of calcium channels'.
While calcium channel blockers exist for synapses (e.g., certain neurotoxins), Cyclosporin A acts downstream of calcium entry by targeting the intracellular enzyme calcineurin, not the membrane channels.
This tests the depth of understanding regarding how NCERT-mentioned bioactive molecules actually interface with cellular signaling.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Neural Control and Coordination - Class 11 |
| Concept | Summation Kinetics |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |