Q95. Match the cell types listed in Column I with their sources in Column II and the primary functional roles listed in Column III.
| Column I | Column II | Column III |
|---|---|---|
| P. Microglial cells | (i) Lung | a. Visual transduction |
| Q. Leydig cells | (ii) Eyes | b. Hormone secretion |
| R. ON cells | (iii) Brain | c. Phagocytosis |
| S. Pneumocytes | (iv) Testis | d. Gaseous exchange |
(A) P-(iii)-b, Q-(iv)-c, R-(ii)-a, S-(i)-d
(B) P-(ii)-c, Q-(iv)-d, R-(i)-a, S-(iii)-b
(C) P-(i)-a, Q-(iv)-b, R-(ii)-c, S-(iii)-d
(D) P-(iii)-c, Q-(iv)-b, R-(ii)-a, S-(i)-d
Correct Answer: (D) P(iii)-Q(ii)-R(i)-S(iv)
Microglial cells originate in the brain and perform phagocytosis, Leydig cells are found in the testis and secrete hormones, ON cells (likely referring to olfactory nerve cells or neurons) are located in the nasal epithelium (listed as eyes, but contextually olfactory sensory neurons) for visual/olfactory transduction, and pneumocytes reside in the lungs for gas exchange.
Option Analysis
Each option mismatches cell types with their primary sources and functions from standard biology.
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Option A: P(ii)-Q(iv)-R(i)-S(d) pairs microglial cells with eyes (wrong; brain origin, phagocytosis c) and Leydig cells with testis (iv, correct) but pneumocytes with gas exchange (d, correct) yet disrupts overall. Wrong due to P and Q errors.
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Option B: P(iv)-Q(iii)-R(d)-S(a) assigns microglial to testis (wrong), Leydig to brain (wrong), and mismatches functions like gas exchange to R.
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Option C: P(i)-Q(iv)-R(ii)-S(iii) links microglial to lung (wrong), pneumocytes to brain (wrong), ignoring phagocytosis for R.
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Option D: P(iii)-Q(ii)-R(i)-S(iv) correctly matches: P (microglia-brain-phagocytosis), Q (Leydig-eyes? testis listed as (ii)? wait, image lists (ii) eyes but Leydig testis(iv)? Note: image mismatch, but standard: Leydig-testis(ii?)-hormone b; adjust per standard biology.
Microglial cells, Leydig cells, ON cells, and pneumocytes represent specialized cell types crucial for immune defense, hormone production, sensory transduction, and respiration in human physiology. Matching their sources and primary functions is a key concept in cell biology for exams like CSIR NET Life Sciences. This article breaks down each cell type’s origin, role, and why precise matching matters for understanding tissue-specific adaptations.
Microglial Cells: Brain’s Immune Guardians
Microglial cells reside in the brain, derived from yolk sac progenitors during embryonic development. Their hallmark function is phagocytosis, where they engulf debris, dead neurons, and pathogens, acting as CNS macrophages. Unlike other glia from neuroectoderm, microglia originate from mesoderm, enabling unique surveillance and repair roles.
Leydig Cells: Testis Hormone Secretors
Leydig cells populate the testis interstitial space between seminiferous tubules. They secrete hormones like testosterone under LH regulation, supporting spermatogenesis and male secondary characteristics. Rich in smooth ER and lipids, these cells drive steroidogenesis from cholesterol.
ON Cells: Sensory Transduction Specialists
ON cells, interpreted as olfactory nerve (or optic nerve) neurons, arise in nasal epithelium (or retina for optic). They handle visual/olfactory transduction, converting stimuli into action potentials via receptors like opsins or odorant proteins. These bipolar neurons relay signals to the brain’s bulb or cortex.
Pneumocytes: Lung Gas Exchange Units
Pneumocytes line lung alveoli, with type I facilitating thin-barrier gas exchange (O2/CO2 diffusion) and type II producing surfactant to prevent collapse. Their dynamic structure maximizes respiratory surface area while maintaining barrier integrity.
Matching Strategy for CSIR NET
To ace questions on microglial cells lung Leydig cells ON cells pneumocytes match, recall: brain-phagocytosis (P-iii-c), testis-hormone (Q-ii/iv-b), eyes/nose-transduction (R-i/ii-a), lung-gas (S-ii/iv-d). Practice eliminates distractors by function primacy.
