The hydroxyl radical is generated from hydrogen peroxide in tissues with abundant iron. Which reaction describes this mechanism?
- A Fenton reaction: Fe2+ + H2O2 yields Fe3+ + OH- + OH radical ✓
- B Haber-Weiss reaction requiring myeloperoxidase
- C Disproportionation of two superoxide molecules by SOD
- D Nitric oxide combining with superoxide to form peroxynitrite
Correct answer: A. Fenton reaction: Fe2+ + H2O2 yields Fe3+ + OH- + OH radical
Explanation
The Fenton reaction uses ferrous iron to split hydrogen peroxide into hydroxyl ion and the highly reactive hydroxyl radical. Iron availability is why hemorrhage and reperfusion amplify oxidative injury. Option C describes superoxide removal, not hydroxyl generation. Peroxynitrite formation (option D) is a distinct radical-generating reaction but does not involve iron or peroxide splitting. Myeloperoxidase produces hypochlorous acid, not hydroxyl radical, and the uncatalyzed Haber-Weiss reaction is too slow to matter physiologically.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.