Hydrogen Oxygen Species ( Ros )

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BACKGROUND Oxygen is abundant in the atmosphere and it is essential for various biochemical processes such as energy production and “biological processes such as metabolic regulation, metabolic energy control, and activation or inactivation of biomolecules, signal transduction, cell exchange, endothelium related vascular functions and gene expression” in most living organisms. Oxidation is the major reaction involved during these processes and it often results in the formation of free radicals as oxygen can oxides other molecules. These free radicals are highly unstable and reactive due to the presence of unpaired orbitals (Magder, 2006). . 2.1. Reactive Oxygen Species (ROS) “Reactive oxygen species (ROS) are radicals or chemical species that partake in reactions that involve gaining or loss of electron (radical reactions) but are not true radicals in that they do not have unpaired electrons”. ROS include non-radical ROS such as hydrogen peroxide (H2O2), and hypochlorous acid (HOCl), ozone (O3) and singlet oxygen (1O2) while radical ROS consist of super oxide anion radicals (O2●-) and hydroxyl radical species (●OH). Besides oxygen-based radicals, reactive nitrogen species(RNS) such as nitric oxide (NO) and nitrogen dioxide (NO2) and peroxynitrile also exist (Magder, 2006). 2.1.1. Formation of ROS Free radicals formation involves the breakage of a chemical bond in molecules such that each fragment keeps one electron, by cleavage of a radical to give another radical and, also
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