Question

When cell components are fractionated by sedimentation, the correct order (from lower to higher gravitational force, g) in which the components get separated is .................

• A. nuclei, mitochondria, microsomes, and ribosomes
• B. microsomes, mitochondria, ribosomes, and nuclei
• C. nuclei, ribosomes, mitochondria, and microsomes
• D. ribosomes, microsomes, mitochondria, and nuclei

Hint:

Remember: In centrifugation, “big pellets first, tiny particles last.” Nuclei sediment at low speed, while ribosomes need ultracentrifugation.

Answer 1

The Correct Option is A

Step 1: Principle of differential centrifugation
- During centrifugation, larger and denser organelles sediment at lower speeds (lower g-force).
- Smaller and lighter components require higher g-forces to sediment. Step 2: Size and density order of organelles
- Nuclei: largest and densest $⇒$ pellet first at low speed.
- Mitochondria: medium size $⇒$ pellet next at intermediate speed.
- Microsomes (vesicles from ER/Golgi): smaller $⇒$ pellet at higher speed.
- Ribosomes: very small $⇒$ require ultracentrifugation at highest speed. Therefore, the order is nuclei $⇒$ mitochondria $⇒$ microsomes $⇒$ ribosomes.