Question 1

Which of the following best describes the main goal of protein purification?

Accepted Answer

To isolate a batch of the same exact protein molecule.

Question 2

A typical protein purification strategy consists of sequential use of several techniques. Which of the following is the correct order for purifying a protein such as TFAM?

Accepted Answer

Extraction $$\rightarrow$$ Dialysis $$\rightarrow$$ Salting Out $$\rightarrow$$ Differential Centrifugation $$\rightarrow$$ Chromatography.

Question 3

During protein extraction, which process is used to break open cells into fragments to release all contents into solution?

Accepted Answer

Homogenization

Question 4

A microbiologist wants to study a new version of beta-galactosidase (lacZ) from E. coli cells. What is the first step in purification?

Accepted Answer

Homogenize the cells to extract lacZ for a later attempt at purification.

Question 5

Centrifugation separates particles in a mixed solution based on which of the following properties?

Accepted Answer

Mass, shape, and density of the particle & solvent.

Question 6

What is the main purpose of differential centrifugation in protein purification?

Accepted Answer

To separate organelles using precise spinning velocities.

Question 7

Which statement best explains the basis of 'salting out' in protein purification?

Accepted Answer

Too many salt ions can deprive proteins of $$H_2O$$ solvent, leading to protein precipitation.

Question 8

Salting out consists of adding __________ in order to __________.

Accepted Answer

Ammonium sulfate; alter the solubility of proteins.

Question 9

Dialysis is a technique used to:

Accepted Answer

Remove salts from a protein solution.

Question 10

Which of the following is a procedure using membrane bags to separate molecules based on molecular size?

Accepted Answer

Dialysis

Question 11

In column chromatography, which statement is true regarding the stationary phase?

Accepted Answer

The stationary phase is a solid material that is immobile during chromatography.

Question 12

Which of the following techniques directly allows for effective separation/purification of a target protein?

Accepted Answer

Column chromatography

Question 13

A scientist is purifying a protein and uses the following steps: Extraction $$\rightarrow$$ Salting Out $$\rightarrow$$ Differential Centrifugation $$\rightarrow$$ Chromatography. What is the main reason for using chromatography last?

Accepted Answer

Chromatography is most effective when the sample size is small.

Question 14

Which property is most important for the sedimentation coefficient ($$S) in $$centrifugation?

Accepted Answer

The greater the $$S$$, the faster the movement of the particle to the bottom to form a pellet.

Question 15

After salting out, a protein solution is placed in a dialysis bag and immersed in a salt solution. What happens to the salts and small molecules?

Accepted Answer

Salts and small molecules diffuse out of the bag through the pores.

Question 16

Which of the following best describes the mobile phase in column chromatography?

Accepted Answer

A liquid material that is mobile and moves during chromatography.

Question 17

Which step in protein purification is most likely to remove unwanted small molecules and salts after salting out?

Accepted Answer

Dialysis

Question 18

Which of the following is NOT a direct effect of adding ammonium sulfate during salting out?

Accepted Answer

Perfectly purifying a protein of interest.

Question 19

A protein solution contains a high concentration of salt after salting out. Which technique should be used next to remove the salt and retain the protein?

Accepted Answer

Dialysis

Question 20

Which of the following statements is true regarding the interaction of proteins with the stationary phase in column chromatography?

Accepted Answer

Proteins with the strongest affinity to the stationary phase are eluted last.

Protein Purification Techniques: Principles and Applications

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