40 Questions
What is the term for the substrate concentration that produces half maximal velocity?
Km
What type of enzyme inhibition can be overcome by high substrate concentration?
Competitive inhibition
What is the effect of a competitive inhibitor on the Kmapp and Vmax of an enzyme?
Kmapp increased, Vmax unaltered
What is the term for the rate of the reaction when all the enzymes are saturated with substrate?
Vmax
What is the purpose of product inhibition in enzyme regulation?
To slow down enzyme activity once enough product is made
What type of inhibition occurs when the product of an enzyme-catalyzed reaction binds to the active site and displaces new substrate?
Competitive inhibition
What is the effect of a competitive inhibitor on the enzyme's ability to attain Vmax?
The enzyme can attain Vmax only if the inhibitor is removed
What is the term for the inhibitor that binds to the active site and prevents product formation?
Non-competitive inhibitor
Where do allosteric effectors bind?
To a site different from the substrate binding pocket
What is the effect of allosteric effectors on enzyme activity?
They increase enzyme activity
What happens to KM in K-type regulation?
It decreases
What type of inhibitor binds to an allosteric site on the protein?
Non-competitive inhibitor
What happens to Vmax in V-type regulation?
It increases
What is the effect of a non-competitive inhibitor on the Km and Vmax of an enzyme?
Km unaltered, Vmax apparent decreased
What are isoenzymes?
Enzymes that catalyze the same reaction but differ in their physical properties
What is the difference between isoenzymes?
Their amino acid sequence
What type of inhibition occurs when an inhibitor binds covalently to a residue within the active site of the enzyme?
Irreversible inhibition
How can isoenzymes be separated from each other?
By electrophoresis
What is the effect of an uncompetitive inhibitor on the Km and Vmax of an enzyme?
Both Km and Vmax are reduced
What is the characteristic of competitive inhibition in Lineweaver-Burk representation?
Only Km is affected
What is the composition of creatine kinase isoenzymes?
A dimer composed of two different polypeptides
What type of inhibitor binds only to the enzyme-substrate complex?
Uncompetitive inhibitor
What is the effect of a non-competitive inhibitor on the enzyme activity at high substrate concentration?
The enzyme activity is decreased
What is the characteristic of non-competitive inhibition in Lineweaver-Burk representation?
Vmax is reduced, Km is unaltered
What happens to enzyme activity when an inhibitor is irreversibly bound?
It is abolished
What type of regulation is not suitable for rapid adaptation?
Enzyme expression
What is the effect of a 10 °C temperature rise on the rate of enzyme-catalyzed reactions?
It doubles the reaction rate
What is the exception to the general rule of enzyme denaturation above 50 °C?
Enzymes from thermophilic bacteria
What is the effect of pH on enzyme activity?
Each enzyme has a specific pH optimum
How can a change in pH affect enzyme activity?
It can affect the binding of substrate, actual catalysis, or the global conformation of the protein
What is the result of an effector binding to the substrate site of an enzyme?
Competitive inhibition
What type of regulation involves the binding of molecules to an enzyme to alter its activity?
Allosteric regulation
What is the composition of Lactate Dehydrogenase (LDH) enzyme?
A combination of two different protein subunits
What is the function of Lactate Dehydrogenase (LDH) isozymes in diagnosis?
To diagnose diseases
What is the role of LDH isozyme in diagnosing myocardial infarction?
To diagnose myocardial infarction
What is the principle of ELISA (enzyme-linked immunosorbant assay)?
Linking an enzyme to an antibody
What is the role of the substrate in ELISA?
To allow for color development
What is the significance of Vmax and KM in enzyme kinetics?
They are used to measure the rate of enzyme reaction
What is the purpose of adding an inhibitor in enzyme kinetics?
To decrease the rate of enzyme reaction
What is the result of an immunological reaction between the antigen and the prepared antibody in ELISA?
The amount of antibody bound to the antigen is proportional to the amount of antigen present
This quiz covers the concepts of enzyme inhibition, regulation of enzyme activity, and uses of enzymes. It is designed for students of Biochemistry 3, Lecture 5.
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