Question 1

How does a centrifuge separate components in a mixture?

Accepted Answer

A centrifuge spins laboratory samples at very high speeds, subjecting them to centrifugal force. This force causes denser particles to migrate away from the axis of rotation while lighter particles move toward it. Dense particles sediment at the tube bottom as a pellet, while the remaining solution, called the supernatant, can be removed and analyzed separately.

Question 2

What is the difference between RPM and RCF in centrifugation?

Accepted Answer

RPM measures revolutions per minute, but it does not directly indicate the force acting on particles. RCF, or relative centrifugal force, quantifies the actual force as a multiple of Earth's gravitational acceleration. Since different centrifuges have different rotor sizes, the same RPM can produce different forces. Using the correct RCF value is critical for successful experiments.

Question 3

Why is balancing tubes critical before centrifugation?

Accepted Answer

Centrifuge rotors reach high speeds and accumulate significant kinetic energy. If tubes are improperly balanced, the entire centrifuge unit can be propelled from its resting place, causing serious damage. Samples must be counterbalanced directly across from each other, or additional counterweight tubes added if needed.

Question 4

What temperature considerations should you make before spinning samples?

Accepted Answer

If using a refrigerated centrifuge, allow the internal temperature to reach the desired value before starting the spin, or find alternative ways to cool the rotor. Temperature control is important for preserving sample integrity during high-speed spinning. Regulating temperature in the lab preserving samples using cold is essential for sensitive biological specimens.

Question 5

What are the main types of centrifuge rotors and their applications?

Accepted Answer

Fixed angle rotors are the most common type, used in differential centrifugation protocols to purify biological specimens like animal cells through multiple washing steps. Swing rotors have flexible tube holders that allow samples to rotate outward, making them ideal for density gradient centrifugation to isolate specific cell types or organelles. Ultracentrifuges spin at over 70,000 RPM for isolating small particles like DNA or viruses.

Question 6

How do you remove and process the separated components after centrifugation?

Accepted Answer

After centrifugation, the pellet appears at the tube bottom. The supernatant can be removed by decanting (pouring it off) or aspirating (using suction). The purified specimen can then be resuspended in fresh solution. Repeating centrifugation, aspiration, and resuspension in buffer is called washing cells, a common purification technique.

Question 7

What safety precautions should you take when operating a centrifuge?

Accepted Answer

Ensure all tube caps are tightened and secure immediately before spinning. Verify that the rotor and lid are properly secured. Start the centrifuge and remain present until it reaches the desired speed. If you notice any problems, call an experienced lab member for assistance. Proper balancing and secure fastening prevent equipment damage and injury.

An Introduction to the Centrifuge - Assessment Quiz