Within neutrophil phagolysosomes, the enzyme myeloperoxidase amplifies microbial killing. Its reaction uses hydrogen peroxide and chloride ion to generate which halogenating species?

• A Singlet oxygen
• B Hypochlorous acid (HOCl) ✓
• C Hydroxyl radical
• D Chloramine gas

Explanation

Myeloperoxidase, a heme enzyme abundant in neutrophil azurophilic granules, catalyses H2O2 plus chloride to hypochlorous acid, the same active agent as household bleach. HOCl is a far stronger bactericidal oxidant than hydrogen peroxide alone and also forms chloramines with amines. Hydroxyl radical arises from the Fenton reaction, a separate iron-catalysed process, which is the key distractor to exclude.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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