Principle of centrifugation MCQs With Answer

Principle of centrifugation MCQs With Answer — For B. Pharm students, understanding the principle of centrifugation is essential for pharmaceutical separation, particle characterization, and quality control. This introduction covers centrifugal force, sedimentation, relative centrifugal force (RCF), rotor types, rpm‑to‑g conversion, and factors affecting separation such as particle size, density, viscosity, and temperature. Mastery of centrifugation theory helps in method development for formulation, plasma/serum preparation, pelleting, ultracentrifugation, and downstream processing. These concise, exam-focused MCQs clarify key concepts and calculations while reinforcing laboratory safety and equipment maintenance. ‘Now let’s test your knowledge with 50 MCQs on this topic.’

Q1. What is the fundamental physical principle behind centrifugation?

• Magnetic attraction of particles
• Application of centrifugal force to accelerate sedimentation
• Covalent bonding of molecules
• Electrostatic repulsion of solutes

Correct Answer: Application of centrifugal force to accelerate sedimentation

Q2. Relative centrifugal force (RCF) depends on which of the following parameters?

• Only rotor speed (rpm)
• Only rotor radius
• Rotor speed and rotor radius
• Sample volume only

Correct Answer: Rotor speed and rotor radius

Q3. Which formula is commonly used to calculate RCF (in g) from rpm and radius (in cm)?

• RCF = 1.118 × 10^-5 × r × (rpm)^2
• RCF = rpm / r
• RCF = r × rpm
• RCF = 9.81 × r × rpm

Correct Answer: RCF = 1.118 × 10^-5 × r × (rpm)^2

Q4. Increasing rpm at constant rotor radius will have what effect on sedimentation?

• No effect
• Decrease sedimentation rate
• Increase sedimentation rate quadratically
• Increase linearly with rpm

Correct Answer: Increase sedimentation rate quadratically

Q5. In centrifugation, the sedimentation coefficient (s) is typically expressed in which unit?

• Seconds (s)
• Svedberg (S)
• Newton (N)
• Revolutions per minute (rpm)

Correct Answer: Svedberg (S)

Q6. Which rotor type is most suitable for pelleting large particles quickly?

• Swinging-bucket rotor
• Fixed-angle rotor
• Analytical rotor
• Low-speed bucketless rotor

Correct Answer: Fixed-angle rotor

Q7. Differential centrifugation separates components primarily based on which property?

• Magnetic susceptibility
• Diffusion coefficient
• Size and density
• Color

Correct Answer: Size and density

Q8. Which centrifugation method is best for separating organelles by size and density using a density gradient?

• Differential centrifugation
• Rate-zonal (velocity) centrifugation
• Filtration
• Dialysis

Correct Answer: Rate-zonal (velocity) centrifugation

Q9. Ultracentrifugation is primarily used to separate what?

• Bulk tablet granules
• Macromolecules like proteins, nucleic acids, and viruses
• Inorganic salts from solution
• Air bubbles from liquids

Correct Answer: Macromolecules like proteins, nucleic acids, and viruses

Q10. Which factor does NOT significantly affect sedimentation rate in a centrifuge?

• Particle density
• Medium viscosity
• Rotor color
• Angular velocity

Correct Answer: Rotor color

Q11. What is the primary safety consideration when loading centrifuge tubes?

• Labeling tubes with color markers
• Balancing tubes symmetrically by mass
• Overfilling the rotor to maximize yield
• Using any tube size available

Correct Answer: Balancing tubes symmetrically by mass

Q12. Which statement about rpm and RCF is correct?

• Equal rpm always yields equal RCF in different rotors
• RCF depends on radius, so equal rpm can yield different RCFs
• RCF is independent of rotor geometry
• RPM is a measure of gravitational force

Correct Answer: RCF depends on radius, so equal rpm can yield different RCFs

Q13. The k-factor of a rotor is used to estimate what?

• Centrifuge power consumption
• Time required for a particle to sediment
• Rotor temperature
• Tube compatibility

Correct Answer: Time required for a particle to sediment

Q14. Which centrifuge is used for analytical determination of sedimentation coefficients?

• Preparative centrifuge
• Analytical ultracentrifuge
• Clinical swing-bucket centrifuge
• Low-speed benchtop centrifuge

Correct Answer: Analytical ultracentrifuge

Q15. What effect does lowering temperature in a refrigerated centrifuge typically have?

• Increases enzyme activity during run
• Reduces degradation of temperature-sensitive samples
• Raises medium viscosity significantly
• Prevents sedimentation entirely

Correct Answer: Reduces degradation of temperature-sensitive samples

Q16. In density gradient centrifugation, where will a particle settle?

• At the top of the gradient irrespective of density
• Where its density equals the local density of the gradient
• At the bottom always
• It will not move in a gradient

Correct Answer: Where its density equals the local density of the gradient

Q17. Which of the following media is commonly used to create density gradients for macromolecule separation?

• Sucrose
• Silica gel
• Polyvinyl chloride
• Ethyl acetate

Correct Answer: Sucrose

Q18. Sedimentation velocity in a centrifuge increases when:

• Particle size decreases
• Viscosity of medium increases
• Difference in density between particle and medium increases
• Temperature is lowered drastically

Correct Answer: Difference in density between particle and medium increases

Q19. Which instrument parameter must be checked to convert rpm to RCF accurately?

• Rotor manufacturer
• Effective radius (distance from center to sample)
• Number of tubes
• Sample color

Correct Answer: Effective radius (distance from center to sample)

Q20. What is a common consequence of rotor imbalance during centrifugation?

• Improved separation resolution
• Vibration and potential rotor damage
• Lowered RCF intentionally
• Increased sample purity

Correct Answer: Vibration and potential rotor damage

Q21. Which rotor is preferred for gradient separations that require minimal disturbance of formed bands?

• Fixed-angle rotor
• Swinging-bucket rotor
• Disposable rotor
• High-speed fixed bucketless rotor

Correct Answer: Swinging-bucket rotor

Q22. In pharmaceutical centrifugation, clarification typically refers to:

• Concentrating active ingredient by evaporation
• Removing suspended particulates from a liquid
• Changing pH of formulation
• Drying wet granules

Correct Answer: Removing suspended particulates from a liquid

Q23. Which parameter is most critical when scaling up a centrifugation process from lab to production?

• Tube color match
• Maintaining equivalent RCF and residence time
• Using same brand of tubes
• Using identical rpm only

Correct Answer: Maintaining equivalent RCF and residence time

Q24. Which type of centrifugation separates particles primarily by buoyant density rather than size?

• Rate-zonal centrifugation
• Isopycnic (equilibrium) centrifugation
• Filtration
• Differential scanning

Correct Answer: Isopycnic (equilibrium) centrifugation

Q25. The sedimentation coefficient s is influenced by which of the following?

• Particle mass, shape, and frictional coefficient
• Only particle color
• Only the rotor speed
• Only the buffer pH

Correct Answer: Particle mass, shape, and frictional coefficient

Q26. Which practice improves recovery of small particles during centrifugation?

• Use lower RCF and longer time (rate-zonal)
• Always use maximum rpm for minimum time
• Use no balancing
• Omit temperature control

Correct Answer: Use lower RCF and longer time (rate-zonal)

Q27. What is a Svedberg unit a measure of?

• Mass of a particle
• Sedimentation coefficient reflecting sedimentation rate
• Volume of a suspension
• Electrical charge of macromolecules

Correct Answer: Sedimentation coefficient reflecting sedimentation rate

Q28. In blood sample preparation, centrifugation is used to separate plasma from cells. Which is correct for standard clinical separation?

• High-speed ultracentrifugation for 24 hours
• Moderate RCF for short time to avoid hemolysis
• No centrifugation; allow to stand overnight
• Use magnetic separation instead

Correct Answer: Moderate RCF for short time to avoid hemolysis

Q29. Which measure reduces rotor corrosion and extends life span?

• Rinsing with saline only
• Regular cleaning, proper lubrication, and avoiding corrosive chemicals
• Storing rotor wet
• Using stronger fasteners than recommended

Correct Answer: Regular cleaning, proper lubrication, and avoiding corrosive chemicals

Q30. What is the main difference between preparative and analytical centrifugation?

• Preparative isolates large quantities; analytical measures properties
• Preparative measures sedimentation coefficient; analytical isolates compounds
• There is no difference
• Preparative always uses lower speeds than analytical

Correct Answer: Preparative isolates large quantities; analytical measures properties

Q31. When calculating RCF for a swinging-bucket rotor, which radius should be used?

• Radius to the top of the bucket
• Effective radius to the sample mid-point or bottom as specified by manufacturer
• Radius of the centrifuge casing
• Radius to the rotor handle

Correct Answer: Effective radius to the sample mid-point or bottom as specified by manufacturer

Q32. What is the effect of increasing medium viscosity on centrifugation?

• Faster sedimentation
• Slower sedimentation and reduced resolution for small particles
• No effect
• Accelerated separation for all particle sizes

Correct Answer: Slower sedimentation and reduced resolution for small particles

Q33. Which of the following is a common indicator of rotor fatigue or damage?

• Unusual vibration or noise at low speeds
• Improved separation efficiency
• Lower room temperature
• Faster acceleration times

Correct Answer: Unusual vibration or noise at low speeds

Q34. Why are sealed buckets or safety cups used in clinical centrifuges?

• To increase rpm beyond rotor limits
• To contain aerosols and biohazards in case of tube breakage
• To increase the rotor radius artificially
• To allow mixing of samples during run

Correct Answer: To contain aerosols and biohazards in case of tube breakage

Q35. Which parameter should be controlled to prevent denaturation of temperature-sensitive proteins during centrifugation?

• pH only
• Temperature (use refrigerated rotor)
• Tube color
• Number of tubes

Correct Answer: Temperature (use refrigerated rotor)

Q36. Which type of centrifugal separation is preferred for purifying viruses by density?

• Gel filtration
• Isopycnic density gradient centrifugation (e.g., CsCl gradient)
• Simple filtration
• Thin-layer chromatography

Correct Answer: Isopycnic density gradient centrifugation (e.g., CsCl gradient)

Q37. What corrective action is appropriate if a centrifuge displays an imbalance error at start?

• Ignore and force start
• Stop and re-balance tubes by mass
• Increase rpm until error clears
• Remove rotor completely

Correct Answer: Stop and re-balance tubes by mass

Q38. Which factor is most important for achieving a tight pellet of cells?

• Low RCF and short time
• Appropriate high RCF and sufficient time
• Use of colored tubes
• Leaving tubes open during run

Correct Answer: Appropriate high RCF and sufficient time

Q39. Centrifugal clarification of fermentation broth in pharma production aims to:

• Separate cells/biomass from the culture supernatant
• Increase broth pH
• Sterilize the broth by heat
• Add nutrients to the broth

Correct Answer: Separate cells/biomass from the culture supernatant

Q40. Which statement about rotor speed limits is correct?

• Using higher than rated rpm is safe if balanced
• Never exceed manufacturer-specified maximum rpm for a rotor
• Rotor speed limits are only suggestions
• Speed limits depend only on tube type

Correct Answer: Never exceed manufacturer-specified maximum rpm for a rotor

Q41. What is the effect of particle shape on sedimentation?

• Shape has no effect
• Non-spherical particles have higher frictional coefficients and sediment more slowly
• All shapes sediment at the same rate as spheres of equal mass
• Only spherical particles can be centrifuged

Correct Answer: Non-spherical particles have higher frictional coefficients and sediment more slowly

Q42. Which of the following is a common gradient medium for nucleic acid separations in ultracentrifugation?

• Polyethylene glycol
• Cesium chloride (CsCl)
• Silicone oil
• Acetone

Correct Answer: Cesium chloride (CsCl)

Q43. What does the term ‘pellet’ refer to in centrifugation?

• The rotor hub
• The aggregated material collected at the bottom of the tube
• The supernatant liquid
• The color change in the sample

Correct Answer: The aggregated material collected at the bottom of the tube

Q44. Which practice ensures reproducible centrifugation results?

• Consistently using the same RCF, time, temperature, and rotor configuration
• Randomizing runtimes each experiment
• Changing buffer composition unpredictably
• Varying rotor type without recording conditions

Correct Answer: Consistently using the same RCF, time, temperature, and rotor configuration

Q45. In a clinical lab, which centrifuge feature helps reduce aerosol formation?

• Open-top rotor
• Sealed safety buckets and lids
• Higher rpm without lids
• Omitting balancing steps

Correct Answer: Sealed safety buckets and lids

Q46. Which equation qualitatively relates sedimentation velocity to particle radius (for small spherical particles in laminar flow)?

• Stokes’ law: velocity proportional to radius squared
• Stokes’ law: velocity proportional to radius
• Ohm’s law
• Arrhenius equation

Correct Answer: Stokes’ law: velocity proportional to radius

Q47. What is the primary use of a refrigerated ultracentrifuge in pharmaceutical research?

• Drying powders
• Isolating temperature-sensitive macromolecules without denaturation
• Heating samples to accelerate reactions
• Colorimetric assays

Correct Answer: Isolating temperature-sensitive macromolecules without denaturation

Q48. For separating subcellular organelles, what strategy is typically used?

• Single short low-speed spin only
• Sequential differential centrifugation with increasing RCF
• Only filtration techniques
• Direct ultrafiltration without centrifugation

Correct Answer: Sequential differential centrifugation with increasing RCF

Q49. Why is it important to use manufacturer-approved tubes and adapters for specific rotors?

• To match color schemes
• To ensure mechanical fit, balance, and safety at rated speeds
• Because they are cheaper
• To improve sample taste

Correct Answer: To ensure mechanical fit, balance, and safety at rated speeds

Q50. When recovering a delicate protein complex after centrifugation in a gradient, the best approach is:

• Vortex the tube to mix layers
• Carefully fractionate the gradient and analyze fractions
• Pour off supernatant quickly
• Heat the tube to 50°C to speed recovery

Correct Answer: Carefully fractionate the gradient and analyze fractions

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com