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How We Produce Free Radicals.* How we produce free radicals* Atoms are most stable in the ground state; an atom is considered to be "ground" when every electron in the outer shell has a complimentary electron that spins in the opposite direction. When free radicals steal an electron from a surrounding compound or molecule a new free radical is formed in its place. In turn the newly formed radical then looks to return to its ground state by stealing electrons with antiparallel spins from cellular structures or molecules; thus the chain reaction continues and can be "thousand of events long." The electron transport chain (ETC), which is found in the inner mitochondrial membrane, uses oxygen to generate energy in the form of adenosine triphosphate (ATP). Oxygen acts as the terminal electron acceptor within the ETC. This is how we produce free radicals. Research suggests that from 2% to 5% of the total oxygen we use during both rest and exercise, has the ability to form the highly damaging superoxide radical. Polyunsaturated fatty acids (PUFAs) are abundant in cell membranes and in low-density lipoproteins (LDL). The PUFAs allow cell membranes to remain fluid. To produce free radicals, a free radical prefers to steal electrons from the lipid membrane of a cell, starting a free radical attack on the cell known as lipid peroxidation. Reactive oxygen species target the carbon-carbon double bond of polyunsaturated fatty acids. The double bond on the carbon weakens the carbon-hydrogen bond allowing for easy dissociation of the hydrogen by a free radical. A free radical will steal the single electron from the hydrogen associated with the carbon at the double bond. In turn this leaves the carbon with an unpaired electron and so becomes a free radical. In an effort to stabilize, the carbon-centered free radical molecular shuffle occurs. The newly arranged molecule is called a conjugated diene (CD). The CD then very easily reacts with oxygen to form a peroxy radical. The peroxy radical steals an electron from another lipid molecule in a process called propagation; this process then continues in a chain reaction and goes on to produce free radicals. When oxygen is energetically excited one of the electrons can jump to empty orbital creating unpaired electrons. Singlet oxygen can then transfer the energy to a new molecule and act as a catalyst for free radical formation. The molecule can also interact with other molecules leading to the formation of a new free radical. This is how we produce free radicals! If all that information is a bit hard to digest; to my understanding, to put it simply, is that free radicals are part of every day living; at times our activities lead us to produce free radicals at a much greater rate than our system can deal with, and sometimes our environment, and choices of foods we eat lead us to produce more free radicals. How we manage to live our lives in this modern world, and how we perceive the importance of making changes in our lives to deal with free radical damage, all comes down to knowledge; if we know the facts, we are empowered to make choices that influence how we feel, and how healthy we actually are, without adding more stress in our lives! Free radicals have been implicated as playing a role in cardiovascular disease, cancer, Alzheimer's disease, and Parkinson's disease. Free radicals formed throughout the day may exceed the protective ability of our antioxidant defense system, making us more susceptible to disease and injury; apart from the antioxidants we get in our foods, there may be a need for antioxidant supplementation. FATIGUE Exercise to produce free radicals? Free radical attack on a membrane usually damages a cell to the point that it must be removed by the immune system, and if the free radicals produced are not controlled in the muscle during exercise a large quantity of muscle could easily be damaged. So far we have only seen the negatives associated with free radical production, however, free radicals produced naturally by the body have beneficial effects that cannot be overlooked. The immune system is the main body system that uses free radicals; invading bacteria, viruses, or damaged tissue are marked with free radicals by the immune system, and this allows the offending material to be removed. Because of this, some people question the need for antioxidant supplementation, as they believe supplementation can actually decrease the effectiveness of the immune system. ANTIOXIDANT DEFENSES Antioxidant means "against oxidation." Antioxidants work to protect lipids from peroxidation by radicals. Antioxidants are effective because they are willing to give up their own electrons to free radicals. When a free radical gains the electron from an antioxidant it no longer needs to attack the cell, and the chain reaction of oxidation is broken. After donating an electron, an antioxidant becomes a free radical. Antioxidants in this state are not harmful because they have the ability to accommodate the change in electrons without becoming reactive. The human body has an elaborate antioxidant defense system. Antioxidants are manufactured in the body, and can also be found in the foods we eat, such as fruits, vegetables, seeds, nuts, meats, and oil. There are two lines of antioxidant defense in the cell. The first line, found in the fat-soluble cellular membrane consists of vitamin E, beta-carotene, and coenzyme Q (10). Of these, vitamin E is considered the most potent chain breaking antioxidant within the membrane of the cell. Inside the cell, water soluble antioxidant scavengers are present. These include vitamin C, glutathione peroxidase, superoxide dismutase (SD), and catalase.
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