Laboratory Instruments: Centrifuge

Questions and Answers

What is the primary function of a centrifuge?

To mix different substances uniformly

To separate solid material from liquid suspension (correct)

To measure the density of liquids

To heat liquids to high temperatures

What principle does a centrifuge operate on?

Evaporation principle

Filtration principle

Condensation principle

Sedimentation principle (correct)

Which three variables are crucial for determining centrifugal force in a centrifuge?

Time, energy, and flow rate

Mass, speed, and radius (correct)

Temperature, volume, and speed

Density, pressure, and area

What happens to blood cells when a centrifuge is used on blood?

They collect at the bottom of the tube Signup and view all the answers

What component of a centrifuge holds the samples during operation?

Head accessories Signup and view all the answers

What is the primary purpose of a hematocrit centrifuge?

To determine the volume fraction of erythrocytes in blood Signup and view all the answers

Which of the following conditions can be assessed using a hematocrit centrifuge?

Polycythemia Signup and view all the answers

Which feature distinguishes a benchtop centrifuge from larger types of centrifuges?

It is compact and suitable for smaller laboratories Signup and view all the answers

How does a benchtop centrifuge generate centrifugal force?

By rotating tubes around a fixed axis Signup and view all the answers

What is the maximum speed that a micro hematocrit centrifuge can reach?

11,000 rpm Signup and view all the answers

What type of motor powers a benchtop centrifuge?

Electric motor Signup and view all the answers

What component does a hematocrit centrifuge use that is similar to a benchtop centrifuge?

Rotors and racks for tubes Signup and view all the answers

What is the RCF capability of a micro hematocrit centrifuge?

15,000 g Signup and view all the answers

What is the maximum speed range for low-speed centrifuges?

4000-5000 rpm Signup and view all the answers

Which type of centrifuge would be best suited for separating DNA and organelles in cells?

Micro centrifuge Signup and view all the answers

At what speed range does a high-speed centrifuge typically operate?

15000-30000 rpm Signup and view all the answers

What is the primary use of an ultracentrifuge?

Separating smaller molecules like proteins Signup and view all the answers

Which centrifuge is primarily used for biochemical applications that require fast operation?

High-speed centrifuge Signup and view all the answers

How does a micro centrifuge typically preform its separation?

At speeds of around 12000-13000 rpm Signup and view all the answers

What safety feature is mentioned for centrifuges?

A micro switch that cuts the current Signup and view all the answers

Which option best describes the primary function of low-speed centrifuges?

For routine sorting of particles in labs Signup and view all the answers

What component of an autoclave ensures that high pressures are maintained during operation?

Hermetically sealed door Signup and view all the answers

Which of the following steps is NOT part of the method of operation for using an autoclave?

Add distilled water above the basket Signup and view all the answers

What is the purpose of the basket in an autoclave?

To load objects to be sterilized Signup and view all the answers

Which item is NOT typically sterilized using an autoclave?

Food items Signup and view all the answers

What function does the tare option on an electronic balance perform?

Sets the display to zero with the container in place Signup and view all the answers

What type of water should be used in an autoclave?

Distilled water Signup and view all the answers

What role does the electrical heater serve in an autoclave?

Provides heat supply Signup and view all the answers

Which of the following best describes the design purpose of a safety valve in an autoclave?

To release excess pressure to prevent explosions Signup and view all the answers

What is the primary method used by an autoclave for sterilization?

High pressure saturated steam Signup and view all the answers

What is the typical temperature and time for sterilization in an autoclave?

134 °C for 15–20 minutes Signup and view all the answers

Which combination is essential for the functioning of an autoclave?

Steam, pressure, and time Signup and view all the answers

What role does pressure play in an autoclave's sterilization process?

It raises the boiling point of water Signup and view all the answers

What is the risk associated with using an autoclave?

Serious injury from hot surfaces and steam Signup and view all the answers

What primarily kills microorganisms in the autoclave process?

Heat from pressurized steam Signup and view all the answers

How does the relationship between pressure and temperature affect the sterilization process?

Higher pressure leads to higher temperature increases Signup and view all the answers

Which of the following materials can be sterilized using an autoclave?

Glassware and metal tools Signup and view all the answers

Study Notes

Centrifuge

Separates solid materials from liquid suspensions using centrifugal force.
Samples are placed in special glass or plastic tubes of various sizes.
Operates on the principle of sedimentation, where denser substances settle at the bottom.
The centrifugal force relies on three variables: mass, speed, and radius.
More dense materials are forced against the walls of the tubes, separating from fluids.

Components of a Centrifuge

Electric motor drives the spinning head that carries samples.
Safety shield is crucial, equipped with a micro switch that cuts power when the lid is opened.
Advanced models may include displays and keyboards for programming speeds.

Types of Centrifuges

Low-Speed Centrifuge:
- Operates at 4000-5000 rpm, commonly used for regular particle sorting.
High-Speed Centrifuge:
- Speeds range from 15,000 to 30,000 rpm, ideal for biochemical applications requiring fast processing.
Ultracentrifuges:
- Operate at extremely high speeds, perfect for separating smaller molecules like proteins and viruses.
Micro Centrifuges:
- Designed for small volumes (0.5-2 µl), usually spin at 12,000-13,000 rpm for cellular organelle separation.
Hematocrit Centrifuge:
- Determines erythrocyte volume fraction in blood samples, operates around 11,000 rpm, useful for various medical tests.
Benchtop Centrifuge:
- Compact, powered by electric motors, versatile for small laboratory spaces, operates tubes around an undetermined axis.

Autoclave

Device for sterilizing equipment and materials using high-pressure saturated steam at 121 °C for 15-20 minutes.
Common sterilization methods include wet heat, dry heat, chemicals, and radiation.
Operates on the principles of steam combined with pressure and time to inactivate microorganisms and spores.

Autoclave Principles

Sterilization relies on the heat of pressurized steam, which can exceed normal boiling temperatures (2.2 bar at 134 °C).
Pressure and temperature are directly proportional; steam allows temperatures to rise, effectively killing microorganisms.

Construction of Autoclaves

Made from strong metal jackets to withstand high pressure.
Features include hermetically sealed doors, pressure gauges, safety valves, thermometers, and electrical heaters.
Commonly used in microbiology, medicine, dentistry, and for sterilizing lab glassware and surgical instruments.

Autoclave Operation Method

Fill with distilled water without exceeding the basket’s bottom.
Place materials in the basket, close and seal the lid.
Adjust settings for temperature, pressure, and time before starting the sterilization cycle.

Balance

Essential lab instrument for measuring chemicals, media, or laboratory animals.
Using an Electronic Balance:
- Place a clean container on the pan, then use the tare function to zero the displayed weight before measurement.

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Description

Explore the fundamentals of the centrifuge, a vital laboratory instrument used for separating solid materials from liquid suspensions through centrifugal force. This quiz will test your understanding of its applications and mechanisms, making it essential for students in laboratory science courses.