A 3-year-old boy presents with recurrent deep abscesses caused by Serratia marcenscens and Aspergillus pneumonia. Dihydrorhodamine flow cytometry shows no oxidative burst. The enzyme complex defective in this patient's neutrophils transfers electrons from which substrate to molecular oxygen to generate superoxide?

• A Ubiquinol
• B NADH
• C FADH2
• D NADPH ✓

Explanation

Chronic granulomatous disease results from defects in the NADPH oxidase (phagocyte oxidase) complex, which transfers electrons from NADPH to O2 to generate superoxide for microbial killing. The DHR test confirms absent respiratory burst. NADH, FADH2, and ubiquinol are mitochondrial electron carriers, not substrates for phagocyte NADPH oxidase.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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