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Free Radicals in Biological Systems
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13618 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
4 / 1988 |
2,354 Words |
| Author
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Karen A. Taylor and Michael G. Simic
Michael G. Simic is a research biochemist specializing in free
radical processes. Karen A. Taylor is a biologist at the
International Life Sciences Institute in Washington, D.C. |
Free radicals are highly reactive, unstable, and short-lived chemical species that, if not controlled, may have devastating effects on biological systems. Free radicals are by-products of certain energy-releasing electron-transfer processes in which oxygen is vital. Yet because oxygen is essential to the lives of most organisms, most living creatures balance precariously between life and death. This balance is maintained by an amazing array of mechanisms that defend against potentially deadly free radicals.
Part II of this three-part series examines free radical processes and their consequences in living systems.
Part I introduced the basic concept of free radicals and surveyed the history and development of the field (see THE WORLD & I, March 1988).
Part III will explore recent discoveries of free radical activity and appropriate treatment in many tissue-damaging traumas caused by disease or injury (forthcoming in THE WORLD & I, May 1988).
On September 13, 1987, two men scavenged a sealed canister containing radioactive cesium-137 (137Cs) from an abandoned radiotherapy clinic in Goiania, Brazil, and sold it to the owner of a junkyard. Thus began a series of events that resulted in the worst radiation accident since Chernobyl. After a workman broke open the shielding around the cesium source, the junkyard owner, unaware of the nature of the contents, was so intrigued by the glowing blue powder that he distributed it to family and friends. Some children even rubbed the luminescent powder on their bodies. Within days, a total of 244 people had been exposed to the radioactive cesium, with the most seriously affected individuals receiving doses between 100 and 800 rad--doses high enough to cause acute radiation sickness and, in four cases, death.
Like the victims at Chernobyl, these four victims died when free radicals generated by radiation reacted destructively in their bodies.
What do radiation exposure, cancer, atherosclerosis, heart disease, and the process by which fats become rancid have in common? All these biologically damaging phenomena involve free radical reactions. To the best of present scientific understanding, free radicals most frequently damage biological systems by altering the genetic material, DNA, or by disrupting cellular membranes. Damage from free radicals may be blocked by certain enzymes and vitamins that
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