38 Questions
What is a common characteristic of proteins that can be exploited to separate them from one another?
Their size, shape, charge, hydrophobicity, and affinity for other molecules
What happens to the electrophoretic movement of larger molecules when an electric field is applied to a solution containing protein molecules?
Their movement is delayed relative to that of smaller molecules
What is the direction of movement of negatively charged proteins in an electric field?
Towards the anode
What is the purpose of the detergent SDS in SDS-PAGE?
To denature protein molecules and mask their intrinsic charge
What is the basis of protein separation in SDS-PAGE?
Molecular weight
What is the function of the gel in Gel Electrophoresis?
To act as a sieve and separate proteins based on their size
What is the ratio of SDS molecules to amino acids in a protein molecule?
One SDS molecule for every two amino acids
What is the purpose of a pH gradient in isoelectric focusing?
To determine the isoelectric point of proteins
Why do proteins stop migrating in isoelectric focusing?
Because they reach a pH equal to their isoelectric point
What is the purpose of staining in gel electrophoresis?
To detect proteins in a gel
Which of the following stains is 50 times more sensitive than Coomassie brilliant blue?
Silver stain
What is the purpose of an immunoblot (Western blot) in gel electrophoresis?
To specifically detect a protein in the presence of many other proteins
What is the term for the pH at which a protein has no net charge?
Isoelectric point
Why do proteins migrate in an electric field?
Because they have a net charge
What is the purpose of blocking the unoccupied binding sites on the nitrocellulose with casein?
To prevent non-specific binding of the antibody
What is the function of the enzyme-linked goat anti-rabbit antibody in immunoblotting?
To catalyze a colorimetric reaction
What is the term for the process of separating proteins based on their isoelectric points in the first dimension and molecular masses in the second dimension?
2D-SDS-PAGE
What is the term for any molecule that induces production of antibodies when introduced in the body of an animal?
Antigen
What is the purpose of the rabbit antibody in immunoblotting?
To bind to the protein of interest
What is the term for the method of separating proteins based on their molecular masses using sodium dodecyl polyacrylamide sulfate?
SDS-PAGE
What is the component of an antibody that binds to the antigen?
Variable region
What does ELISA stand for?
ENZYME-LINKED IMMUNOSORBENT ASSAY
What is the purpose of the enzyme in ELISA?
To convert a colorless substrate to a colored product
When was ELISA developed?
1970
What can ELISA be used to detect?
Either antigens or antibodies
What is immobilized on a solid support in ELISA?
Antibody
What is the role of the second antibody in ELISA?
To covalently link to an assayable enzyme
What is the purpose of incubating with a protein-containing sample in ELISA?
To allow antigen-antibody binding
What is the result of the enzyme converting the substrate in ELISA?
A colored product
What is the use of ELISA in estimating?
Nanograms to picograms
What is the benefit of using ELISA?
It is a powerful method
What is the main purpose of enzyme assays?
To study enzyme kinetics and enzyme inhibition
Under what conditions are enzyme assays typically performed?
At optimal pH, temperature, and ionic strength
What is the significance of measuring enzyme activity in serum?
It is an indicator of tissue damage
What is the purpose of adding high concentrations of substrate in enzyme assays?
To ensure the enzyme is working at its maximum level
What is the diagnostic significance of enzyme assays in metabolic disease?
It detects specific enzymes that are absent or present at lower levels
What is the role of ions or cofactors in enzyme assays?
They are necessary for enzyme action
What is the significance of elevated levels of a specific enzyme in serum?
It is an indicator of tissue damage caused by a disease
This quiz covers various methods for analyzing proteins, including gel electrophoresis, immunological techniques, and enzyme assays.
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