Free radicals and reactive oxygen species

Free Radicals and reactive oxygen species

1. Prepared by : Deepa Devkota Roll no :07 Human Biology 7 th 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 10 –9 –10 –12 sec) Collide with another molecule and either abstract or donate an electron to achieve stability

3. Types of free radicals 1. Superoxide, O 2 - 2. Hydrogen peroxide, H 2 O 2 3. Hydroxyl radical, OH - 4. Singlet oxygen, 1 O 2 5. Hydroperoxy radical, HOO - 6. Lipid peroxide radical, ROO - 7. Nitric oxide, NO - 8. peroxynitrite , ONOO -

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, o ne antioxidant molecule can react with a single free radical So there must be a constant need to replenish its resources

5. Antioxidants Enzymatic antioxidants Superoxide dismutase,catalase,glutathione peroxidase,glutathione reductase 2.Nutrient antioxidants β - carotene, α tocopherol,ascorbic acid 3.Metabolic antioxidants Bilirubin,uric acid,ceruloplasmin,ferritin,transferrin,albumin,glutathione

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 radic al

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 liver’s 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: Parkinson’s disease Alzheimer’s disease multiple sclerosis, liver cirrhosis muscular dystrophy.

12. REFERENCES Harper’s illustrated biochemistry,28 th edition Marks Dawn B. ,basic medical biochemistry, a clinical approach sciencedirect.com/science/article/ pii /S0891584900002525(retrieved on 17 th january,2015) slideshare.net/guest371c9f/free-radicals(retrieved on 15 th january 2015)