Question 1:
What is the main principle behind isoelectric focusing?
Explanation: The correct answer is B) Separation based on charge. The main principle behind isoelectric focusing is the separation of charged molecules based on their isoelectric point (pI). The molecules migrate in a pH gradient within a gel or capillary until they reach a region where the pH matches their pI. At the pI, the molecules have no net charge, causing them to stop migrating and form distinct bands.
Question 2:
What is the pH of the anode in isoelectric focusing?
Explanation: The correct answer is B) Basic. In isoelectric focusing, the pH at the anode (positive electrode) is typically set to be basic. This establishes an acidic-to-basic pH gradient across the gel or capillary, allowing the migration of acidic molecules towards the anode. The pH gradient facilitates the separation of molecules based on their pI values.
Question 3:
Which type of gel is commonly used in isoelectric focusing?
Explanation: The correct answer is B) Polyacrylamide gel. Polyacrylamide gel is commonly used in isoelectric focusing. It provides a stable matrix for the separation of charged molecules based on their pI values. The polyacrylamide gel is cast with a pH gradient, allowing the migration and separation of molecules based on their different pI values.
Question 4:
What is the purpose of ampholytes in isoelectric focusing?
Explanation: The correct answer is A) Establishing the pH gradient. Ampholytes are small molecules with a range of pI values that are added to the gel or capillary in isoelectric focusing. They establish the pH gradient across the separation medium, covering the entire range of pH values. This pH gradient helps create the conditions necessary for the migration and separation of analytes based on their pI values.
Question 5:
What is the detection method commonly used in isoelectric focusing?
Explanation: The correct answer is D) Staining with Coomassie Brilliant Blue. After isoelectric focusing, proteins are typically visualized by staining the gel with Coomassie Brilliant Blue or other protein stains. Coomassie Brilliant Blue binds to proteins and forms a blue-colored complex, allowing the detection and quantification of protein bands based on their intensity in the gel.
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