Questions and Answers
What is the maximum angular speed of a microcentrifuge?
What type of centrifuge is best for isolating smaller biological particles like ribosomes and proteins?
Which centrifuge is specifically designed to maintain low temperatures?
How much liquid can a high-speed centrifuge typically handle?
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What is the maximum angular velocity achievable by ultracentrifuges?
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Which feature is unique to cold centrifuges compared to other types?
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What is a typical volume that microcentrifuge tubes can hold?
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Which centrifuge can reach speeds over 65,000 x g?
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What is a common application for a high-speed centrifuge?
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Which of the following centrifuges is primarily used for high-velocity applications?
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Study Notes
Types of Centrifugal Separations
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Differential Centrifugation: Separates particles based on size; larger particles sediment faster than smaller ones during centrifugation.
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Used for obtaining partially pure preparations of subcellular organelles and macromolecules.
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Resulting pellet contains a mixture from larger to smaller particles; supernatant consists of liquid plus most slowly sedimenting components.
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Density Gradient Centrifugation: Preferred method for purifying subcellular organelles and macromolecules by creating density gradients with multiple layers of gradient media.
Types of Centrifuge
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Microcentrifuge:
- Designed for small volumes (0.5 - 2.0 mL).
- Spun at speeds of 12,000–13,000 rpm.
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High-speed or Superspeed Centrifuge:
- Handles larger sample volumes, from tens of milliliters to several liters.
- Achieves higher speeds, around 30,000 rpm.
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Ultracentrifuge:
- Utilizes high centrifugal forces to study biological particles.
- Can isolate much smaller particles, including ribosomes and viruses, reaching speeds over 70,000 rpm.
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Cold Centrifuge:
- Maintains low temperatures (-20°C to -40°C), ideal for sensitive analyses such as DNA, RNA, and proteins.
- Achieves speeds over 30,000 rpm, with a relative centrifugal force (RCF) exceeding 65,000 x g.
Centrifuge Functionality
- A centrifuge separates particles from solutions based on size, shape, density, viscosity, and rotor speed by applying high gravitational force.
- Denser particles sink while lighter ones rise; if densities are equal, particles remain in suspension.
- Commonly used to separate macromolecules like cells, organelles, proteins, nucleic acids (DNA, RNA), and salts.
Principle of Centrifugation
- Operates on the sedimentation principle; denser substances settle at the bottom of the tube.
- In blood centrifugation, blood cells gather at the bottom, while plasma remains at the top.
- Variables impacting centrifugal force include mass, shape, speed, and radius.
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Description
Learn about differential centrifugation, a method for separating particles based on size, commonly used for obtaining partially pure preparations of subcellular organelles and macromolecules.
