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Micronutrients 2

4 Pages

Course Code
NUTR 3210
Genevieve Newton

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Micronutrients 2 Reactive Oxygen Species • Molecules that contain oxygen which are ‘reactive’ can react with, and do damage, to molecules in the body • They are formed as a consequence of the reactions of energy metabolism, which involve redox reactions in an aerobic environment (continuous leakage of electrons from ETC) • Transfer of a single electron to O2  superoxide anion radical • Superoxide anion radical can react with a single electron to form hydrogen peroxide (superoxide dismutases) • Hydrogen peroxide ideally will react with glutathione in the reaction catalyzed by glutathione peroxidase to form water, but it can also react with a single electron to form the hydroxyl radical which is really reactive and can cause cell death and cancer. Vitamin E • A family of 8 compounds (4 tocopherols and 4 tocotrienols), but only alpha-tocopherol contributes to the RDA since it is the only one that properly fits the tocopherol transfer protein (TTP) • Acts as a single electron donor (from OH group) • Several possible stereoisomers of alpha- tocopherol  only the RRR (natural) form fits the TTP perfectly • The main role of vitamin E is as a chain breaking antioxidant in lipid peroxidation  it can react with a PUFA (polyunsaturated fatty acid) peroxyradical to form a tocopherol radical and a PUFA hydroperoxide •If the hydroxyl radical forms, it picks up another hydrogen atom from a PUFA (or other molecules, but we’ll only look at this one) •Hydroxyl radical becomes water, and stable. PUFA becomes PUFA radical. It’s very reactive. It reacts with water to become PUFA peroxyradical, which is more stable. •If vitamin E isn’t present, PUFA peroxyradical reacts with another PUFA to form PUFA hydroperoxide and other PUFA radical (chain reaction): • If vitamin E is present, tocopherol can donate an electron to PUFA peroxyradical to form PUFA hydroperoxide and Vitamin E radical which is pretty stable. • The vitamin E radical is stable but will either dimerize, form a quinone, or possibly be regenerated to active (non-radical) vitamin E by vitamin C (?) •PUFA hydroperoxide can be converted to
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