Q.22 Which ofthe following organelle is pelleted first during sub-cellular fractionation by differential
centrifugation at 1000 g for 10 minutes
1. Nuclei
2. Mitochondria
3. Lysosome
4. Endoplasmic reticulum
Correct Answer: 1. Nuclei
Nuclei, the largest and densest organelles (5-10 μm), sediment first at low-speed centrifugation (1000 g for 10 min), while smaller organelles remain in supernatant for higher-speed pelleting.
Option Analysis
1. Nuclei
~600-1000 g pellets nuclei cleanly due to large size/density. Standard first step in differential centrifugation protocols for cell fractionation.
2. Mitochondria
Require 10,000-15,000 g (20-30 min) due to smaller size (0.5-1 μm). Low speed leaves them suspended.
3. Lysosome
Sediment at ~20,000-25,000 g with mitochondria or higher. Too small/light for 1000 g pelleting.
4. Endoplasmic reticulum
Forms microsomes pelleted at 80,000-100,000 g ultracentrifugation. Remains in supernatant at low speeds.
Organelle pelleted first 1000g differential centrifugation nuclei establishes the standard protocol for subcellular fractionation in cell biology research. This organelle pelleted first 1000g differential centrifugation nuclei guide details sedimentation sequence for molecular biology students preparing competitive exams.
Centrifugation Protocol Steps
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1000g, 10 min: Nuclei pellet (P1)
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10,000g, 20 min: Mitochondria/lysosomes (P2)
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100,000g, 60 min: Microsomes (ER, Golgi) (P3)
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Supernatant: Cytosol, ribosomes. Size dictates speed: larger = lower g.
Sedimentation Order Table
| Speed (g) | Time | Pellet Contents | Size Range |
|---|---|---|---|
| 1000 | 10 min | Nuclei | 5-10 μm |
| 10,000-15,000 | 20 min | Mitochondria | 0.5-1 μm |
| 20,000 | 20 min | Lysosomes | 0.2-0.5 μm |
| 100,000 | 60 min | ER microsomes | 0.05-0.1 μm |
Organelle pelleted first 1000g differential centrifugation nuclei prevents contamination of later fractions.
Exam Applications
Critical for enzyme assays, proteomics. Mnemonic: “Nuclei = 1K g (like 1st gear); Mitochondria = 10K (10x harder).”
