How do free radicals damage cells and tissues

Among the major cellular and extracellular targets for reactive radical species are proteins, unsaturated fatty acyl components of lipids and lipoproteins, and DNA constituents including carbohydrates, as is depicted in Fig. 2.9. 

Recent review articles (Halliwell and Gutteridge, 1984 Slater, 1984  

Kappus, 1985) have concluded that oxygen-derived free radical spe- 

Lipid peroxidation may beinitiated by any primary free radical which has sufficient reactivity to extract a hydrogen atom (Fig. 2.10) from a reactive methylene group of an unsaturated fatty acid. For example, species such as hydroxyl radicals OH, alkoxyl radicals RO peroxyl radicals ROO and alkyl radicals R may be involved. The formation of the initiating species is accompanied by bond rearrangement that results in stabilization by diene conjugate formation. The lipid radical then takes up oxygen to form the peroxyl radical. Peroxyl radicals can 

Lipid hydroperoxides are fairly stable molecules under physiological conditions, but their decomposition is catalysed by transition metals and metal complexes (O Brien, 1969). Both iron(II) and iron(III) are effective catalysts for hydroperoxide degradation, but the former is more so (Halliwell and Gutteridge, 1984). These include complexes of iron salts with low molecular weight chelates, non-haem iron proteins, free haem, haemoglobin, myoglobin. 

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