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 10–9–10–
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
11. 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
12. 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
13. 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
14.
15.
16. REFERENCES
Harper’s 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)