Q.101 Golgi apparatus is also termed as cellular post office, since it packages and transports cellular
proteins across various organelles and outside the cell. In general, the Golgi is perinuclear in
location and is closely associated with the endoplasmic reticulum. A chemical compound,
Monensin inhibits all trafficking from Golgi. If Golgi is visualized by immunofluorescence
microscopy after treatment with this compound, the Golgi will be
(A) absent (B) normal (C) swollen (D) fragmented
Monensin inhibits Golgi trafficking by disrupting its acidic pH gradient as a Na+/H+ ionophore, causing cisternae to swell due to osmotic water influx after ion accumulation. When visualized by immunofluorescence after treatment, the Golgi appears swollen. The correct answer is option (C).
Correct Answer
(C) Swollen
Mechanism of Monensin
Monensin neutralizes the acidic environment in trans-Golgi cisternae, halting protein transport from Golgi to vesicles/lysosomes. This blocks proton pumps, allows Na+ entry, and triggers osmotic swelling starting at the trans-Golgi network, progressing to cis/medial cisternae—visible as enlarged, vacuolated structures in microscopy across animal/plant cells.
Option Analysis
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(A) Absent: Incorrect. Golgi proteins (e.g., GM130, TGN46) remain detectable; monensin relocates but doesn’t degrade the organelle.
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(B) Normal: Wrong. Trafficking block causes rapid structural disruption (within 2-5 min), altering perinuclear ribbon into swollen stacks.
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(C) Swollen: Correct. EM and IF show cisternae expansion from ion/water imbalance; trans elements swell first, forming blebs/vesicles.
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(D) Fragmented: Incorrect. Brefeldin A fragments Golgi into ER; monensin swells intact stacks without dispersing mini-stacks.
Introduction to Monensin Golgi Effects
In monensin golgi swollen immunofluorescence studies for GATE Life Sciences, Q.101 tests Golgi visualization after trafficking inhibition. The “cellular post office” swells due to pH disruption, key for understanding protein secretion blocks in perinuclear ER-associated Golgi.
Monensin Action on Golgi
Monensin, an ionophore, exchanges Na+ for H+ in acidic Golgi compartments, causing osmotic swelling of trans-cisternae first. IF microscopy reveals enlarged, vacuolated Golgi stacks, not absence or fragmentation.
Q.101 Step-by-Step Solution
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Monensin halts all Golgi trafficking.
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pH neutralization → ion influx → water entry → swelling.
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IF detects swollen Golgi via markers like giantin.
Answer: (C) Swollen—matches EM/IF data in mammalian/plant cells.
Option Breakdown for Exams
| Option | Why Incorrect/Correct | Evidence |
|---|---|---|
| (A) Absent | Proteins persist | No degradation |
| (B) Normal | Rapid disruption | 2-5 min changes |
| (C) Swollen | Osmotic effect | Trans-cisternae first |
| (D) Fragmented | Unlike brefeldin | Stacks intact |
GATE Cell Biology Tips
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Compare: Monensin (swell) vs. Brefeldin (fragment) vs. Nocodazole (disperse).
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Mnemonic: “Monensin Makes Golgi Mighty (swollen).”
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High-yield: Visualize via IF/EM for trafficking questions.
Master monensin golgi swollen immunofluorescence for top GATE scores in cell biology.
