Aspirin's irreversible inhibition of platelet COX-1 is clinically significant because platelets lack which cellular organelle, preventing recovery of COX activity?

• A Nucleus (anucleate) ✓
• B Mitochondria
• C Endoplasmic reticulum
• D Lysosomes

Explanation

Mature platelets are anucleate — they lack a nucleus and therefore cannot synthesise new protein, including COX-1. When aspirin irreversibly acetylates the serine residue at the COX-1 active site, the platelet cannot replace the enzyme. Inhibition lasts for the platelet's entire lifespan (7–10 days). New platelets must be released from megakaryocytes before thromboxane A2 synthesis is restored, which is why antiplatelet effects persist for nearly the full platelet lifespan.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.