Intracellular iron overload potentiates oxidative injury in many diseases. Which reaction accounts for the generation of the most reactive oxygen species capable of initiating lipid peroxidation in membranes?

• A Conversion of superoxide to hydrogen peroxide by superoxide dismutase
• B Reduction of hydrogen peroxide to water by catalase
• C Production of hypochlorous acid by myeloperoxidase in phagolysosomes
• D Reaction of hydrogen peroxide with ferrous iron to produce the hydroxyl radical ✓

Explanation

The Fenton reaction, in which ferrous iron reacts with hydrogen peroxide to yield hydroxyl radicals and hydroxide ions, generates the hydroxyl radical, the most reactive and damaging of the reactive oxygen species. Hydroxyl radicals initiate lipid peroxidation by abstracting protons from unsaturated fatty acids in membranes, propagating chain reactions of membrane destruction. Superoxide dismutase and catalase are protective antioxidant enzymes. Myeloperoxidase-derived HOCl is a bactericidal agent in neutrophils, not the principal membrane-damaging radical.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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