Activated macrophages generate nitric oxide via inducible nitric oxide synthase. The direct microbicidal species formed when nitric oxide combines with superoxide radicals inside the phagolysosome is:
- A Hypochlorous acid
- B Hydroxyl radical
- C Peroxynitrite ✓
- D Nitrogen dioxide radical
Correct answer: C. Peroxynitrite
Explanation
NO produced by iNOS reacts spontaneously with superoxide anion to form peroxynitrite (ONOO-), a potent reactive nitrogen species that damages microbial DNA, proteins, and lipids. Hypochlorous acid arises from the myeloperoxidase halide system, a separate oxygen-dependent pathway, and hydroxyl radical forms from Fenton chemistry rather than the NO-superoxide reaction. Nitrogen dioxide is a minor downstream product, not the primary species formed.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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