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Measuring Affinity and KD of Drugs

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Questions and Answers

What is the primary method used to measure the affinity of an agonist?

Plotting a dose-response curve for the agonist
Using a radioactive-labeled ligand with isolated cell membranes (correct)
Measuring the physiological response to the agonist
Comparing concentration response curves for agonist and antagonist

What is the relationship between receptor occupancy and physiological response?

Inverse, with response decreasing as occupancy increases
Linear, with a direct correlation between occupancy and response
Hyperbolic, with a maximum response at high occupancy
Sigmoidal, with a threshold occupancy needed for response (correct)

What is the purpose of comparing concentration response curves for agonist and agonist + antagonist?

To measure the affinity of the agonist
To measure the efficacy of the agonist
To determine the receptor occupancy of the agonist
To measure the affinity of the antagonist (correct)

What is the relationship between the logarithmic concentration scale and the receptor occupancy curve?

Sigmoidal, with a threshold log(concentration) needed for occupancy (B) Signup and view all the answers

What is the difference between affinity and efficacy?

Affinity refers to the ability to bind, while efficacy refers to the ability to activate a receptor (C) Signup and view all the answers

What is the primary function of a receptor in relation to an agonist?

To switch from its resting state to its activated state upon binding of the agonist (C) Signup and view all the answers

What is the effect of an antagonist on the fractional occupancy of an agonist?

It decreases the fractional occupancy of the agonist. (A) Signup and view all the answers

What is the purpose of the dose ratio in reversible competitive antagonism?

To determine the concentration of the agonist needed to produce the same response in the presence of the antagonist. (C) Signup and view all the answers

What is the effect of increasing the concentration of an antagonist on the receptor occupancy of an agonist?

It decreases the receptor occupancy of the agonist. (B) Signup and view all the answers

What is the unit of the equilibrium dissociation constant for the antagonist (KB)?

Concentration (D) Signup and view all the answers

What is the effect of the antagonist on the RT in the presence of an agonist?

It increases the RT. (A) Signup and view all the answers

What is the relationship between the dose ratio (r) and the EC50 values in the absence and presence of the antagonist?

r = [A`]/[A] (B) Signup and view all the answers

What is the definition of efficacy in the context of receptor binding?

The ability of a drug to activate a receptor once bound (A) Signup and view all the answers

A drug has an efficacy of 0.5. What type of drug is it?

Partial agonist (D) Signup and view all the answers

What is the term for the minimum amount of drug required to produce a certain biological response?

EC50 (B) Signup and view all the answers

A full agonist can achieve a maximum response without activating all receptors. What is this phenomenon known as?

Receptor reserve (B) Signup and view all the answers

What is the term for the ability of a drug to bind to a receptor?

Affinity (B) Signup and view all the answers

What is the main assumption of the two-state receptor model?

Receptors can adopt an active state even in the absence of an agonist (C) Signup and view all the answers

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