Question 1

Which two properties are used to separate proteins in two-dimensional (2D) gel electrophoresis?

Accepted Answer

Isoelectric point (pI) and molecular weight (MW)

Question 2

During the first dimension of 2D electrophoresis, proteins are separated based on their:

Accepted Answer

Isoelectric point ($pI$)

Question 3

What is the role of sodium dodecyl sulfate (SDS) in the second dimension of 2D gel electrophoresis?

Accepted Answer

It denatures proteins and imparts a uniform negative charge

Question 4

A protein spot on a 2D gel is found at a high $pI$ and low molecular weight. What does this indicate about the protein?

Accepted Answer

It is basic and small

Question 5

If two proteins have identical molecular weights but different isoelectric points, how will they appear on a 2D gel?

Accepted Answer

They will be aligned horizontally but at different positions along the $pI$ axis

Question 6

Which of the following best describes the order of separation in 2D gel electrophoresis?

Accepted Answer

First by isoelectric point, then by molecular weight

Question 7

A researcher runs a 2D gel and observes two spots at the same $pI$ but different molecular weights. What does this suggest?

Accepted Answer

The proteins have the same isoelectric point but different sizes

Question 8

Why is it important to use a denaturing agent like SDS in the second dimension of 2D electrophoresis?

Accepted Answer

To ensure proteins are separated solely by molecular weight

Question 9

Which of the following statements about 2D gel electrophoresis is FALSE?

Accepted Answer

It separates proteins only by their molecular weight

Question 10

A protein sample is subjected to 2D gel electrophoresis. After the first dimension, the proteins are equilibrated in SDS before the second dimension. What is the main reason for this step?

Accepted Answer

To impart a uniform negative charge and denature the proteins

Question 11

If a protein is not denatured before the second dimension of 2D electrophoresis, what is the most likely outcome?

Accepted Answer

It may not migrate according to its true molecular weight

Question 12

Which of the following is a real-world application of 2D gel electrophoresis?

Accepted Answer

Comparing protein expression profiles in healthy vs. diseased tissues

Question 13

A 2D gel shows two spots with the same molecular weight but different $pI$ values. What could explain this observation?

Accepted Answer

Post-translational modifications altering the charge of the protein

Question 14

Which of the following best explains why 2D gel electrophoresis can resolve thousands of proteins from a single sample?

Accepted Answer

It separates proteins by two independent properties: $pI$ and $MW$

Question 15

A protein with a $pI$ of 5.0 and a molecular weight of 50 kDa is run on a 2D gel. Where would you expect to find it?

Accepted Answer

At the position corresponding to $pI = 5.0$ and $MW = 50,000$ Da

Question 16

Which of the following is NOT a limitation of 2D gel electrophoresis?

Accepted Answer

It cannot separate proteins by their amino acid sequence

Question 17

In a clinical laboratory, 2D gel electrophoresis is used to compare serum proteins from patients with and without a disease. What is the most likely goal of this experiment?

Accepted Answer

To identify disease-specific protein biomarkers

Question 18

Which step in 2D gel electrophoresis ensures that proteins are separated by their isoelectric point?

Accepted Answer

Isoelectric focusing

Question 19

A protein sample is subjected to 2D gel electrophoresis, and a spot is observed at $pI = 7.0$ and $MW = 25,000$ Da. If the same protein undergoes phosphorylation, where would you expect the new spot to appear?

Accepted Answer

At a lower $pI$ but similar $MW$

Question 20

Which of the following best describes the principle of isoelectric focusing used in 2D gel electrophoresis?

Accepted Answer

Proteins migrate in a pH gradient until they reach a pH equal to their $pI$

2D Electrophoresis: Principles and Applications in Protein Analysis

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