Which free radical is the MOST reactive oxygen species (ROS) and is responsible for initiating lipid peroxidation chain reactions in biological membranes?

• A Superoxide anion (O2•⁻)
• B Hydrogen peroxide (H2O2)
• C Singlet oxygen (1O2)
• D Hydroxyl radical (•OH) ✓

Explanation

The hydroxyl radical (•OH) is the most reactive ROS, generated primarily by the Fenton reaction (Fe2+ + H2O2 → Fe3+ + •OH + OH⁻) and the Haber-Weiss reaction (O2•⁻ + H2O2 → O2 + •OH + OH⁻). •OH has an extremely short half-life (~10⁻⁹ s) and reacts at diffusion-limited rates with virtually all biomolecules. It initiates lipid peroxidation by abstracting a hydrogen atom from polyunsaturated fatty acid side chains, generating a lipid radical that undergoes chain propagation. Vitamin E (alpha-tocopherol) is the primary chain-breaking antioxidant in membranes, donating H• to lipid radicals and terminating the chain.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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