Free-Radical Damage

Free-Radical Damage

Write A Short Note On Free Radical Injury.
Answer:

Free radicals are chemical species with an unpaired electron in their outer orbit. These free radicals react with both inorganic and organic molecules, which are present in membranes and nucleic acids.

Free radical damage

“Understanding free radicals: Causes and effects”

Causes Of Free Radical Injury

Free radical generation is induced by

• Absorption of radiant energy, i.,e. UV rays, X-rays.
• Enzymatic metabolism of exogenous chemical/drugs, i.e. CCl₄ to CCl^–₃
• Reduction—oxidation reaction processes that occur during normal metabolism, i.e.,.e. formation of superoxide anion (O₂^–). Hydrogen peroxide (H₂O₂) hydroxyl ion (OH^–).
• Reactions involving transition metals, i.e., iron (Fenton reaction), copper, etc.
• Reactions involving nitric oxide (NO,) which acts as a free radical and can be converted to highly reactive peroxynitrite anion (ONOO^– as well as NO₂ and NO₃^–.

Effects of free radicals

“Importance of reducing free-radical damage for health”

Effects Of Free Radical Injury

The hydroxyl radical is the most reactive species. It may produce membrane damage by the following mechanisms:

• Lipid peroxidation: Polyunsaturated fatty acids of the membrane are attacked repeatedly and severely by oxygen-derived free radicals to yield highly destructive polyunsaturated fatty acid radicals, i.,e. lipid hydroperoxy radicals and lipid hydroperoxides. This reaction is termed as lipid peroxidation. Lipid peroxidation is propagated to other si,tes causing widespread membrane damage and destruction of organelles.
• Oxidation of proteins: Oxygen-derived free radicals cause cell injury by oxidation of protein macromolecules of cells, cross-linking of labile amino acids, as well as by fragmentation of polypeptides directly. The result is the degradation of cytosolic neutral proteases and cell destruction.
• DNA damage: Free radicals cause breaks in the single strands of nuclear and mitochondrial DNA. This results in cell injury, and it may also cause malignant transformation of cells.
• Cytoskeletal damage: Reactive oxygen species are also known to interact with cytoskeletal elements and interfere in mitochondrial aerobic phosphorylation and thus cause ATP depletion.

Antioxidants and free radicals

“Emerging research on antioxidants and free-radical damage”

The antioxidants are used to inactivate the free radicals.

Inactivation Of Free Radicals

Inactivation of free radicals is done by:

• Antioxidants, i.e., vitamins A, C, E, and β carotene.
• Iron and copper-binding proteins, i.e., transferrin, ferritin. lactoferrin, ceruloplasmin
• Enzymes such as catalase, superoxide dismutase, and glutathione peroxidase.