Pharmacology Pharmacodynamics and Mechanism of Action 3

Question 1

An irreversible antagonist differs from a competitive antagonist primarily because it:

Accepted Answer

Cannot be overcome by increasing agonist concentration

Answer

Irreversible antagonists form covalent bonds with the receptor, so increasing agonist concentration cannot fully displace them or restore maximal response.

Question 2

Which term describes the concept that a receptor can adopt an active conformation spontaneously, independent of agonist binding?

Accepted Answer

Constitutive activity

Answer

Constitutive (basal) activity occurs when receptors spontaneously adopt an active conformation without agonist binding, producing measurable effects.

Question 3

Nitroglycerin exerts its vasodilatory effect by serving as a source of which signaling molecule?

Accepted Answer

Nitric oxide (NO)

Answer

Nitroglycerin is bioconverted to nitric oxide, which activates soluble guanylyl cyclase to increase cGMP, causing smooth muscle relaxation.

Question 4

A drug that causes receptor desensitization through phosphorylation of the receptor by G protein-coupled receptor kinases (GRKs) is most likely:

Accepted Answer

A sustained agonist

Answer

GRKs phosphorylate activated GPCRs after sustained agonist exposure, leading to beta-arrestin recruitment and receptor desensitization.

Question 5

In a quantal dose-response curve, the ED50 represents the dose that produces the desired effect in what percentage of the population?

Accepted Answer

50%

Answer

ED50 in a quantal dose-response relationship is the dose producing the specified effect (e.g., analgesia) in 50% of the test population.

Pharmacology Practice Test

Pharmacology Practice Test

Pharmacology Pharmacodynamics and Mechanism of Action 3