Q.69 Which one of the following transport mechanism is NOT employed by prokaryotes?
(A) Passive diffusion (B) Group translocation (C) Endocytosis (D) Active transport
Prokaryotes lack the cytoskeletal machinery and membrane dynamics required for endocytosis, relying instead on membrane protein-based transport systems. The correct answer is (C) Endocytosis.
Correct Answer
(C) Endocytosis
Prokaryotic Transport Mechanisms
Prokaryotes (bacteria/archaea) use a rigid cell wall and plasma membrane for nutrient uptake via protein transporters. They employ passive diffusion for small hydrophobic molecules (O2, CO2), active transport (ABC transporters, P-type ATPases) against gradients, and group translocation (e.g., phosphotransferase system modifies glucose during uptake). Endocytosis—requiring pseudopod formation and vesicle pinching—is exclusive to eukaryotes with flexible membranes.
Option Analysis
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(A) Passive diffusion: Correct for prokaryotes. Simple diffusion moves nonpolar gases/small molecules down gradients without energy/proteins.
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(B) Group translocation: Correct prokaryotic mechanism. Substrates chemically altered during transport (e.g., PTS system phosphorylates sugars), preventing efflux.
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(C) Endocytosis: NOT employed. No phagocytosis/pinocytosis in prokaryotes; lacks actin/dynamin for vesicle formation.
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(D) Active transport: Correct. ATP-driven (primary) or ion-gradient coupled (secondary) via symporters/antiporters.
Introduction to Prokaryotes Transport Mechanisms
Prokaryotes transport mechanism endocytosis questions like GATE Life Sciences Q.69 test key differences: bacteria use protein-mediated diffusion/translocation but lack endocytosis due to rigid walls. Option (C) identifies the eukaryotic-exclusive process.
Prokaryotic vs Eukaryotic Transport
| Mechanism | Prokaryotes | Eukaryotes | Example |
|---|---|---|---|
| Passive diffusion | Yes | Yes | O2 across lipid bilayer |
| Group translocation | Yes | No | Bacterial PTS (glucose-P) |
| Endocytosis | No | Yes | Phagocytosis/macropinocytosis |
| Active transport | Yes | Yes | Na+/K+ ATPase |
Rigid peptidoglycan prevents membrane invagination in prokaryotes.
Q.69 Detailed Elimination
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A/D: Standard bacterial membrane transport.
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B: Unique prokaryotic modification-during-transport.
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C: Absent—requires cholesterol/actin absent in bacteria.
Answer: (C) confirmed by microbiology texts.
Why Endocytosis Fails in Prokaryotes
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Rigid cell wall blocks membrane deformation.
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No cytoskeleton (actin, microtubules) for vesicle formation.
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Small size (~1-5 μm) favors surface transporters over bulk engulfment.
Prokaryotes achieve equivalent via outer membrane porins (Gram-) and periplasmic binding proteins.
GATE Microbiology Exam Tips
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Mnemonic: “Proks Pump, Don’t Pinch” (active transport, no endocytosis).
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Compare: Group translocation = prokaryote-only.
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High-yield: ABC transporters (ATP-binding cassette) for most active uptake.
Master prokaryotes transport mechanism endocytosis distinctions for perfect cell biology scores.
