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1. Prepared by : Deepa Devkota Roll no :07 Human Biology 7th
batch Free radicals and reactive oxygen species
2. FREE RADICALS highly reactive molecular species with an
unpaired electron, persists only for very short duration(of the
order of 10910 12 sec) Collide with another molecule and either
abstract or donate an electron to achieve stability
4. Antioxidants:the scavengers of free radicals Present in low
concentration that significantly delays or inhibits oxidation of
substrate antioxidant sacrifices itself by becoming oxidized,one
antioxidant molecule can react with a single free radical
6. Reactive oxygen species Major oxygen metabolites produced by
one electron reduction of oxygen
7. Hydroxyl radicals are the most potent ROS
8. Lipid peroxidation by hydroxyl radical
9. Biological effects of free radicals DNA: chemical changes
that if not repaired can inherited to daughter cells Proteins:
Oxidative damage to sulfhydryl group and tyrosine residues in
protein can lead to formation of oxygen radicals by non enzymatic
reactions formation of proteins that are recognized as non self by
immune system leading to cross reaction causing autoimmune
diseases
10. Biological effects of free radicals Chemical modification
of protein or lipids in plasma low density lipoprotein leads to
abnormal LDL which arenot recognized by livers LDL receptors
Modified LDL is taken by macrophage scavenger receptor,forms lipid
engorged macrophages(LEM), infiltrate under blood vessel
endothelium Killing of LEM by high content of unesterified
cholesterol forming atherosclerotic plaques
11. Free radicals and diseases Respiratory diseases: destroy
endothelium and cause lung edema Cigarette smoke contains free
radicals and promotes the production of more free radicals Diabetes
mellitus: Destruction of islets results in pathogenesis Cataract
Male infertility: reduce sperm motility and viability Ageing
process Others: Parkinsons disease Alzheimers disease multiple
sclerosis, liver cirrhosis
12. REFERENCES Harpers illustrated biochemistry,28th edition
Marks Dawn B. ,basic medical biochemistry, a clinical approach
sciencedirect.com/science/article/pii/S0891584900 002525(retrieved
on 17th january,2015)
slideshare.net/guest371c9f/free-radicals(retrieved on 15th january
2015)