Question 1

Which of the following factors does NOT directly affect the sedimentation rate of a particle during centrifugation?

Accepted Answer

Temperature of the rotor

Question 2

During centrifugation, particles move toward the bottom of the tube primarily because:

Accepted Answer

The centrifugal force overcomes the buoyant force

Question 3

Which equation best describes the sedimentation coefficient $s$ in terms of mass $m$, frictional coefficient $f$, and the buoyant force (where $\rho$ is the density of the solvent and $v$ is the partial specific volume)?

Accepted Answer

$s = \frac{m(1-\rho v)}{f}$

Question 4

A researcher wants to isolate mitochondria from a cell homogenate. Which centrifugation technique should be used for the initial separation?

Accepted Answer

Differential centrifugation

Question 5

In differential centrifugation, why are multiple spins at increasing speeds used?

Accepted Answer

To sequentially pellet particles of decreasing size and density

Question 6

Which of the following best explains why the pellet forms at the bottom of the tube during centrifugation?

Accepted Answer

Centrifugal force causes denser particles to move outward and sediment

Question 7

A student performs differential centrifugation and finds that the supernatant still contains nuclei. What is the most likely reason?

Accepted Answer

The centrifugation time or speed was insufficient to pellet the nuclei

Question 8

Which of the following is the main purpose of differential centrifugation?

Accepted Answer

To separate cell fractions and organelles with similar $s$ values

Question 9

If a particle has a higher mass and a lower frictional coefficient, what will happen to its sedimentation coefficient $s$?

Accepted Answer

$s$ will increase

Question 10

Which of the following statements about the sedimentation coefficient $s$ is TRUE?

Accepted Answer

$s$ depends on both the mass and the frictional coefficient of the particle

Question 11

A scientist is using differential centrifugation to isolate lysosomes. After the first spin, which fraction is most likely to contain the lysosomes?

Accepted Answer

Supernatant after removing nuclei and mitochondria

Question 12

Which of the following would increase the rate at which a particle sediments during centrifugation?

Accepted Answer

Increasing the rotor speed

Question 13

Why is it important to keep samples cold during differential centrifugation?

Accepted Answer

To prevent protein denaturation and preserve organelle integrity

Question 14

Which of the following best describes the relationship between centrifugal force ($F_c$), mass ($m$), angular velocity ($\omega$), and radius ($r$) in centrifugation?

Accepted Answer

$F_c = m \omega^2 r$

Question 15

A sample is spun at a higher speed in a centrifuge. What is the expected effect on the sedimentation of particles?

Accepted Answer

Particles will sediment more rapidly

Differential Centrifugation: Principles and Applications in Biochemistry

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