Image Caption : superoxide ion - With one unpaired electron, the superoxide ion is a free radical. Free radicals are highly unstable molecules that can damage cells. Free radicals are produced in the course of normal metabolic processes (some free radicals, in fact, play useful roles in the body), but they can also be produced by exposure to environmental contaminants, tobacco smoke, radiation or UV light on the skin.
The action of free radicals depends on the transfer of electrons from one molecule to another. Free radicals steal electrons from molecules in cells, in the process causing cell damage that may lead to conditions such as the inflammation of vessel walls (which can cause plaque buildup) and damage to cellular DNA which can lead to cancer. Free radical damage may also play a role in the development of degenerative diseases such as Alzheimer`s, Parkinson`s and rheumatoid arthritis. The gradual accumulation of free radicals over time is believed by many to be responsible for the process of aging.
In this model, oxygen atoms are red.
Highly reactive molecules with an unsatisfied electron valence pair. Free radicals are produced in both normal and pathological processes. They are proven or suspected agents of tissue damage in a wide variety of circumstances including radiation, damage from environment chemicals, and aging. Natural and pharmacological prevention of free radical damage is being actively investigated.
National Center for Biotechnology Information, U.S. National Library of Medicine
What are free radicals?
Free radicals are highly reactive atoms formed when oxygen interacts with certain molecules. They try to "steal" electrons from atoms in body tissues, and in doing so can damage cellular components such as cell membranes and DNA, and lead to heart disease, cancer, and other diseases.
Free radicals are formed in the normal processes of energy metabolism, but they are also created by environmental pollution, cigarette smoke, and toxic chemicals. To prevent free radical damage, your body has several enzyme systems that scavenge free radicals. Problems start when the body is inundated by so many free radicals that it can't cope with them all. Micronutrients, such as vitamin E, beta-carotene, and vitamin C, in addition to the thousands of phytochemicals now being discovered in many fruits and vegetables, can aid the body in eliminating damaging free radicals.
The Free Radical Theory
The free radical theory on aging was originally proposed in the 1950s, and still remains under debate. Generally speaking, the free radical theory of aging suggests that accumulated cellular damage from oxidative stress contributes to the physiological and anatomical effects of aging. There are two significantly different versions of this theory: one states that the aging process itself is a result of oxidative damage, and the other states that oxidative damage causes age-related disease and disorders. The latter version of the theory is more widely accepted than the former. However, many lines of evidence suggest that oxidative damage does contribute to the aging process. Research has shown that reducing oxidative damage can result in a longer lifespan in certain organisms such as yeast, worms, and fruit flies. Conversely, increasing oxidative damage can shorten the lifespan of mice and worms. Interestingly, a manipulation called calorie-restriction (moderately restricting the caloric intake) has been shown to increase life span in some laboratory animals. It is believed that this increase is at least in part due to a reduction of oxidative stress. However, a long-term study of primates with calorie-restriction showed no increase in their lifespan. A great deal of additional research will be required to better understand the link between reactive oxygen species and aging.
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