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Question 1:

What is the purpose of SDS-PAGE in protein analysis?

A) Determining protein concentration
B) Separating proteins based on size
C) Analyzing protein structures
D) Identifying protein-protein interactions

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Explanation: The correct answer is B) Separating proteins based on size. SDS-PAGE is commonly used in protein analysis to separate proteins based on their molecular weight or size. By denaturing the proteins with sodium dodecyl sulfate (SDS) and subjecting them to electrophoresis in a polyacrylamide gel matrix, proteins can be separated and visualized based on their migration distance in the gel.

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Question 2:

What is the role of SDS in SDS-PAGE?

A) Stabilizing the gel matrix
B) Enhancing protein detection
C) Reducing disulfide bonds
D) Denaturing the proteins

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Explanation: The correct answer is D) Denaturing the proteins. SDS (Sodium Dodecyl Sulfate) plays a crucial role in SDS-PAGE by denaturing the proteins. It binds to proteins and coats them with a negative charge in proportion to their mass, leading to uniform charge-to-mass ratio. This allows the proteins to be separated based on their size during electrophoresis.

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Question 3:

What is the purpose of a stacking gel in SDS-PAGE?

A) Increasing separation resolution
B) Denaturing the proteins
C) Concentrating the protein samples
D) Reducing the gel porosity

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Explanation: The correct answer is A) Increasing separation resolution. A stacking gel is used in SDS-PAGE to enhance the resolution of protein separation. It has a higher concentration of acrylamide compared to the separating gel, creating a sieving effect. The stacking gel allows for the focused stacking of proteins into a narrow zone, improving the separation efficiency during electrophoresis.

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Question 4:

What is the purpose of a reducing agent in SDS-PAGE?

A) Stabilizing the gel matrix
B) Enhancing protein detection
C) Breaking disulfide bonds
D) Denaturing the proteins

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Explanation: The correct answer is C) Breaking disulfide bonds. A reducing agent is used in SDS-PAGE to break disulfide bonds in proteins. Common reducing agents like dithiothreitol (DTT) or β-mercaptoethanol reduce the disulfide bonds, helping to unfold and denature proteins before electrophoresis. This ensures that the separation is based solely on the molecular weight of the proteins.

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Question 5:

Which stain is commonly used to visualize proteins in an SDS-PAGE gel?

A) Coomassie Brilliant Blue
B) Ethidium Bromide
C) SYBR Green
D) Silver stain

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Explanation: The correct answer is A) Coomassie Brilliant Blue. Coomassie Brilliant Blue is a commonly used stain to visualize proteins in an SDS-PAGE gel. It binds to proteins and forms a blue-colored complex, allowing the detection and quantification of protein bands. Other staining methods, such as silver stain or fluorescent dyes, can also be used for protein visualization in SDS-PAGE.