1. 1. Prepared by : Deepa Devkota Roll no :07 Human Biology 7th batch Free radicals and reactive oxygen species
2. 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
3. 3. Types of free radicals 1. Superoxide, O2 - 2. Hydrogen peroxide, H2O2 3. Hydroxyl radical, OH- 4. Singlet oxygen, 1O2 5. Hydroperoxy radical, HOO- 6. Lipid peroxide radical, ROO- 7. Nitric oxide, NO- 8. peroxynitrite, ONOO-
4. 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
5. 5. Antioxidants 1. Enzymatic antioxidants Superoxide dismutase,catalase,glutathione peroxidase,glutathione reductase 2.Nutrient antioxidants - carotene, tocopherol,ascorbic acid 3.Metabolic antioxidants Bilirubin,uric acid,ceruloplasmin,ferritin,transferrin,al bumin,glutathione
6. 6. Reactive oxygen species Major oxygen metabolites produced by one electron reduction of oxygen
7. 7. Hydroxyl radicals are the most potent ROS
8. 8. Lipid peroxidation by hydroxyl radical
9. 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. 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. 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. 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)