Question 1

Which of the following best describes the principle behind dialysis as used in biochemistry for protein purification?

Accepted Answer

Proteins are retained while small molecules diffuse through a semi-permeable membrane due to size exclusion.

Question 2

During dialysis, which of the following best explains why small ions move out of the dialysis bag while proteins remain inside?

Accepted Answer

The semi-permeable membrane allows only molecules below a certain size to pass through, so small ions diffuse out while proteins are retained.

Question 3

A researcher wants to remove ammonium sulfate from a protein solution after precipitation. Which technique should they use?

Accepted Answer

Dialysis

Question 4

Which equation best describes the rate of diffusion of a solute across a dialysis membrane?

Accepted Answer

$ J = -D \frac{dC}{dx} $

Question 5

If a protein solution is dialyzed against a large volume of buffer, what will happen to the concentration of small ions in the protein solution over time?

Accepted Answer

It will decrease as small ions diffuse out until equilibrium is reached.

Question 6

Which of the following is NOT a typical use of dialysis in a biochemistry laboratory?

Accepted Answer

Separating proteins based on their charge

Question 7

A dialysis bag containing a protein solution is placed in a beaker of pure water. Which direction will water move, and why?

Accepted Answer

Water will move into the bag due to higher protein concentration inside.

Question 8

Which property of the dialysis membrane is most critical for its function in separating proteins from small molecules?

Accepted Answer

Its molecular weight cutoff (MWCO)

Question 9

A protein solution is dialyzed against a buffer with a lower salt concentration. What is the main driving force for the movement of salt ions?

Accepted Answer

Concentration gradient

Question 10

Which of the following scenarios would result in incomplete removal of small molecules during dialysis?

Accepted Answer

Dialyzing against a small volume of buffer that is not changed frequently

Question 11

Which of the following best explains why proteins do not diffuse out of the dialysis bag during the process?

Accepted Answer

Proteins are too large to pass through the pores of the dialysis membrane.

Question 12

A scientist wants to exchange the buffer of a protein solution from phosphate buffer to Tris buffer. Which technique should they use?

Accepted Answer

Dialysis

Question 13

Which of the following would increase the rate of dialysis for small molecules?

Accepted Answer

Increasing the concentration gradient across the membrane

Question 14

If a protein solution is dialyzed against a buffer containing a high concentration of urea, what is a likely outcome?

Accepted Answer

The protein will denature due to urea diffusing into the bag.

Question 15

Which of the following is the best reason for changing the dialysis buffer multiple times during the process?

Accepted Answer

To maintain a high concentration gradient for efficient removal of small molecules.

Dialysis: Principles and Applications in Biochemistry

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