Week 5: Protein Techniques 2

Question 1

What is SDS-PAGE used for?

Answer 1

Separation of proteins by size

SDS-PAGE allows accurate determination of mass.

Question 2

What does SDS stand for?

Answer 2

Sodium dodecyl sulfate

SDS is a detergent that denatures proteins.

Question 3

How does SDS affect proteins in SDS-PAGE?

Answer 3

Denatures proteins and provides a uniform charge-to-mass ratio

1 molecule of SDS binds for every two amino acids.

Question 4

What is the isoelectric point (pI) of a protein?

Answer 4

The pH at which a molecule has no net charge

It depends on the relative amounts of acidic and basic side chains.

Question 5

What is the purpose of isoelectric focusing?

Answer 5

Separation of proteins based on their isoelectric point

Proteins migrate to their isoelectric point in a pH gradient.

Question 6

What is two-dimensional gel electrophoresis?

Answer 6

A technique combining isoelectric focusing and SDS-PAGE for high-resolution separation

First separates proteins by isoelectric point, then by size.

Question 7

What technique is used for protein purification by size?

Answer 7

Gel-filtration chromatography

Proteins are separated based on their size.

Question 8

What technique is used for protein purification based on charge?

Answer 8

Ion-exchange chromatography

Proteins are separated based on their net charge.

Question 9

What technique is used for protein purification based on binding affinity?

Answer 9

Affinity chromatography

It separates proteins based on their specific interactions.

Question 10

What is the role of a glass-Teflon homogenizer in protein purification?

Answer 10

Preparation of a cell extract

It helps in breaking down cells to release proteins.

Question 11

True or False: DNA and RNA can be separated by size using agarose gels.

Answer 11

True

Agarose gels are specifically used for nucleic acid separation.

Question 12

What is the migration of proteins in gel electrophoresis based on?

Answer 12

Charge and size

Proteins migrate in an electrical field through the gel.

Question 13

Fill in the blank: The first step in two-dimensional gel electrophoresis is _______.

Answer 13

Isoelectric focusing

Question 14

What is the primary purpose of gel electrophoresis?

Answer 14

To separate nucleic acids and proteins

This technique is crucial in molecular biology for analyzing biomolecules.