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Pharmacodynamics and Mechanism of Action Flashcards

7 cards from real Pharmacology practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Pharmacodynamics and Mechanism of Action flashcards as text

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

    Answer: Cannot be overcome by increasing agonist concentration

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

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

    Answer: Constitutive activity

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

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

    Answer: Nitric oxide (NO)

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

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

    Answer: A sustained agonist

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

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

    Answer: 50%

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

  6. Which enzyme is directly inhibited by sildenafil, leading to increased cGMP levels and penile erection?

    Answer: Phosphodiesterase type 5 (PDE5)

    Sildenafil inhibits PDE5, which normally degrades cGMP, thereby prolonging cGMP-mediated smooth muscle relaxation and vasodilation.

  7. The term 'biased agonism' refers to a drug that:

    Answer: Selectively activates specific downstream pathways of a receptor over others

    Biased agonists preferentially activate one signaling pathway (e.g., G protein vs. beta-arrestin) over another at the same receptor, enabling pathway-selective pharmacology.