Question 1

Which of the following best describes the principle behind 'salting out' in protein purification?

Accepted Answer

High salt concentration competes with proteins for water molecules, decreasing protein solubility and causing precipitation.

Question 2

During the 'salting out' process, why does the addition of salt cause proteins to precipitate?

Accepted Answer

Salt ions compete for water molecules, reducing the hydration shell around proteins and promoting aggregation.

Question 3

Which salt is most commonly used in the 'salting out' technique for protein purification?

Accepted Answer

Ammonium sulfate

Question 4

What is the effect of increasing salt concentration on protein-protein interactions during 'salting out'?

Accepted Answer

It strengthens protein-protein interactions, leading to precipitation.

Question 5

Which of the following equations best represents the relationship between protein solubility ($S$) and salt concentration ($[Salt]$) during 'salting out'?

Accepted Answer

$S \propto \frac{1}{[Salt]}$

Question 6

In a protein purification experiment, a researcher adds ammonium sulfate to a solution containing several proteins. Which protein will precipitate first?

Accepted Answer

The protein with the lowest solubility at the given salt concentration.

Question 7

Why is ammonium sulfate preferred over sodium chloride for 'salting out' proteins?

Accepted Answer

Ammonium sulfate is less likely to denature proteins due to its high solubility and gentle ionic strength.

Question 8

A protein solution is subjected to increasing concentrations of salt. At low salt concentrations, protein solubility increases. What is this phenomenon called?

Accepted Answer

Salting in

Question 9

Which of the following best explains why 'salting out' can be used to purify a specific protein from a mixture?

Accepted Answer

Different proteins have different solubilities at various salt concentrations, allowing selective precipitation.

Question 10

Which statement is FALSE regarding the mechanism of 'salting out'?

Accepted Answer

Salting out increases protein solubility indefinitely.

Question 11

A researcher wants to purify a protein using 'salting out'. Which step should be performed after precipitation?

Accepted Answer

Centrifuge the solution to collect the precipitated protein.

Question 12

Which of the following is NOT a consequence of adding excess salt during 'salting out'?

Accepted Answer

Protein solubility will increase indefinitely.

Question 13

In the context of 'salting out', what does the term 'hydration shell' refer to?

Accepted Answer

The layer of water molecules surrounding a protein, stabilizing its solubility.

Question 14

Which of the following graphs best represents the relationship between protein solubility and salt concentration during 'salting in' and 'salting out'?

Accepted Answer

A curve that increases at low salt concentration ('salting in') and decreases at high salt concentration ('salting out').

Question 15

Which of the following is a practical application of 'salting out' in biochemistry?

Accepted Answer

Purification of proteins from cell lysates.

Question 16

A solution contains two proteins, A and B. Protein A precipitates at 40% ammonium sulfate, while protein B precipitates at 60%. How can you selectively purify protein A?

Accepted Answer

Add ammonium sulfate to reach 40%, collect the precipitate, and remove the supernatant.

Question 17

Which of the following statements about 'salting out' is TRUE?

Accepted Answer

It is a reversible process; proteins can be redissolved by removing the salt.

Question 18

What is the main reason that 'salting out' is effective for protein purification?

Accepted Answer

Different proteins have unique solubility profiles at different salt concentrations.

Question 19

Which of the following steps is NOT involved in the 'salting out' process?

Accepted Answer

Heating the solution to denature proteins.

Question 20

In a 'salting out' experiment, what would happen if the salt concentration is too low?

Accepted Answer

Proteins remain soluble and do not precipitate.

Salting Out: Protein Solubility and Purification

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