Reactive Oxygen Species and Antioxidants
Start with the big picture
ROS include superoxide, hydrogen peroxide, hydroxyl radicals, and singlet oxygen. They arise from sources such as mitochondrial electron-transport-chain leakage, cytochrome P450, xanthine oxidase, NADPH oxidase, and ionizing radiation. Haber–Weiss and Fenton reactions can generate hydroxyl radicals, which contribute to lipid peroxidation, DNA damage, and protein modification. Oxidative stress occurs when ROS generation exceeds antioxidant capacity and is associated with several disease processes and aging. Defenses include superoxide dismutases, catalase, and glutathione peroxidase, supported by glutathione recycling through NADPH. Small-molecule antioxidants have complementary roles: vitamin E interrupts lipid peroxidation chains, while vitamin C scavenges aqueous radicals and helps regenerate vitamin E. The full lesson develops these mechanisms and their clinical context.
What you'll learn
- Identify major reactive oxygen species and their cellular sources.
- Describe how Haber–Weiss and Fenton reactions generate hydroxyl radicals.
- Relate ROS damage to oxidative stress and cellular dysfunction.
- Compare the roles of enzymatic and small-molecule antioxidant defenses.
- Explain how glutathione, NADPH, and selenium support antioxidant enzyme function.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
