Riboflavin deficiency produces cheilosis, glossitis, and corneal vascularization. Which electron transport chain complex directly contains a flavoprotein requiring riboflavin-derived FAD?

• A Complex I (NADH dehydrogenase)
• B Complex II (succinate dehydrogenase) ✓
• C Complex III (cytochrome bc1)
• D Complex IV (cytochrome c oxidase)

Explanation

Succinate dehydrogenase, Complex II, is a flavoprotein containing covalently bound FAD that transfers electrons from succinate to ubiquinone. Complex I uses FMN, which is also riboflavin-derived, but the classic examined flavoprotein of the respiratory chain is Complex II. Complexes III and IV contain iron-sulfur centers, cytochromes, and copper, with no flavin requirement, eliminating those options.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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