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Free radicals

Terms in this set (10)

Free radicals are
chemical species with an unpaired electron in their outer orbit.
Physiologic generation of free radicals occurs during
oxidative phosphorylation. 1. Cytochrome c oxidase (complex IV) transfers electrons to oxygen. 2. Partial reduction of 0 2 yields superoxide (0:), hydrogen peroxide (H2 O), and hydroxyl radicals ("OH).
Pathologic generation of free radicals arises with
1. Ionizing radiation-water hydrolyzed to hydroxyl free radical 2. Inflammation-NADPH oxidase generates superoxide ions during oxygendependent killing by neutrophils. 3. Metals (e.g., copper and iron)-Fe2 + generates hydroxyl free radicals (Fenton reaction). 4. Drugs and chemicals-P450 system of liver metabolizes drugs (e.g., acetaminophen), generating free radicals.
Free radicals cause cellular injury via
peroxidation of lipids and oxidation of DNA and proteins; DNA damage is implicated in aging and oncogenesis.
Elimination of free radicals occurs via multiple mechanisms
.1. Antioxidants (e .g., glutathione and vitamins A , C, and E)
Elimination of free radicals occurs via multiple mechanisms
2. Enzymes i. Superoxide dismutase (in mito)_ ii. Glutathione peroxidase (in mitochondria)iii. Catalase (in peroxisomes)
Elimination of free radicals occurs via multiple mechanisms
3. Metal carrier proteins (e.g., transferrin and ceruloplasmin)
the most damaging free radical
(OH) free radical
Carbon tetrachloride (CC1 4 ) and fatty liver mechanism
.Converted to CC13 free radical by P450 system of hepatocytes .Results in cell injury with swelling of RER; consequently, ribosomes detach, impairing protein synthesis. . Decreased apolipoproteins lead to fatty change in the liver
why there is continued rise in cardiac enzymes (e.g., troponin) after reperfusion of infarcted myocardial tissue
Return of blood to ischemic tissue results in production ofO2 -derived free radicals, which further damage tissue.
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