Topic overview

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Antioxidant defense combines enzymes that catalytically convert reactive oxygen species with non-enzymatic compounds that scavenge radicals or interrupt oxidative chain reactions. Superoxide dismutase converts superoxide to hydrogen peroxide, which catalase or glutathione peroxidase can further decompose. Glutathione supports peroxide removal and detoxification, while glutathione reductase uses NADPH to restore its reduced form. Vitamins E and C contribute complementary protection: vitamin E acts in lipid environments, and vitamin C can help regenerate it. The lesson also relates antioxidant systems to required trace elements and clinical examples, including vitamin deficiencies and increased acetaminophen toxicity when glutathione is depleted. Together, these systems illustrate how the balance between reactive oxygen species and antioxidant capacity matters in health and disease.