40 Questions
What is the term for the increase or decrease in binding affinity of other sites due to the binding of an effector molecule?
Allosterism
What type of allosteric modulator is a substrate for its target enzyme?
Homotropic
What is the term for the increase in binding affinity of other molecules due to the binding of one molecule?
Positive cooperativity
What is the term for the decrease in binding affinity of other molecules due to the binding of one molecule?
Negative cooperativity
What type of allosteric modulator is not a substrate for its target enzyme?
Heterotropic
What is the term for the regulation of an enzyme's activity by a substance that binds at a second site?
Allosteric regulation
What is the term for a protein that has its biological activity affected by the binding of other substances?
Allosteric enzyme
What is the term for the inhibition of an enzyme's activity by a substance that binds at a second site?
Negative allosterism
What is the example of an enzyme that is regulated by both its substrate and other molecules?
Hemoglobin
What is the term for the regulation of an enzyme's activity by a substrate?
Homotropic regulation
What is the primary mechanism by which allosteric control regulates enzyme activity?
Conformational changes induced by effector binding
What is the most common type of reversible covalent modification?
Phosphorylation
What is the term for the process by which an enzyme is activated by cleavage of non-active protein?
Proteolytic activation
What is the characteristic exhibited by allosteric enzymes?
Cooperativity
What is the term for the binding of small molecules to an enzyme at sites other than the active site?
Allosteric control
What is the result of effector binding to an allosteric enzyme?
Conformational changes in the enzyme
What is the term for the changes that occur when a binding site of a protein or receptor is activated or deactivated?
Cooperativity
What is the primary difference between allosteric and proteolytic activation?
Binding of small molecules vs. cleavage of non-active protein
What is the term for the attachment of a phosphate group to a protein?
Phosphorylation
What is the characteristic of allosteric enzymes that allows them to exhibit cooperativity?
Multiple binding sites
What does the enzyme CTP synthetase catalyze?
The ATP-dependent transfer of the amide nitrogen from glutamine to the C-4 position of UTP
What type of regulation is used by feedback inhibition?
Allosteric regulation
What is the organization of the ATCase catalytic unit?
6 subunits organized into 2 trimers
How many models are used to explain allosterism and cooperativity?
Two
What is the name of the model proposed by Wyman, Monod, and Changeux in 1965?
The Concerted Model
What is the main feature of the Sequential Model?
The binding of substrate induces a conformational change from the T form to the R form
What is unique to the Sequential Model of behavior?
Negative cooperativity
What is the main difference between the Concerted Model and the Sequential Model?
The Concerted Model has all subunits in the same conformation, while the Sequential Model has subunits in different conformations
What is the induced-fit model of substrate binding?
A model where the enzyme is flexible and the active site reshapes to fit the substrate
What is the function of allosteric activators in the Concerted Model?
To bind to and stabilize the R (active) form
What is the principle behind the induced-fit protocol of substrate binding?
The active site adjusts to fit the substrate.
What is the result of substrate binding to one subunit of an enzyme?
The binding sites of other subunits are more receptive to substrate.
What is the purpose of phosphorylation in enzyme activity?
To activate or deactivate the enzyme.
What is the term for the inactive precursor of an enzyme that is converted to its active form by proteolysis?
Proenzyme.
What is the role of a coenzyme in an enzymatic reaction?
To take part in the reaction and be regenerated for further reaction.
What is the function of NAD+ in redox reactions?
To accept electrons from the reaction.
What is the effect of substrate binding to an enzyme on its activity?
It increases the activity of the enzyme.
What is the term for the process of adding or removing a phosphate group from an enzyme?
Phosphorylation.
What is the result of phosphorylation on a serine, threonine, or tyrosine residue?
It creates a phosphate ester.
What is the purpose of a zymogen?
To be stored in an inactive form and later activated.
Test your knowledge of biological control methods, including allosteric control and reversible covalent modification, which affect enzyme activity.
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