Free Radical Effects on Membranes

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As would be expected, the cell has defensive mechanisms against this kind of damage. Endogenous antioxidants such as vitamin E, ascorbate, ceruloplasmin, transferrin, and cysteine help protect membranes from oxidant injury. Enzymes such as superoxide dismutase, glutathione peroxidase and catalase neutralize free radicals. Any interference with these protective mechanisms can result in membrane damage by oxidants. Can you envision a mechanism by which vitamin E and selenium deficiency could result in cell injury?

Click here for answer. What is the major component of the cell membrane? Abnormalities in the cytoskeleton result in membrane damage.

The cytoskeleton composed of microfilaments, intermediate filaments and microtubules serves as a structural support system and transport system for the cell. Detachment of the cytoskeleton from the plasma membrane caused by cell swelling or drug intoxication cytochalasin results in membrane "blebs" and ultimately renders the cell membrane much more susceptible to lysis. Damage to the cells energy supply and damage to the cell membrane are only 2 of many mechanisms of cell injury.

We have only covered two of the most important mechanisms of cell injury disruption of the energy supply and membrane damage.

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Direct damage to DNA or the protein synthesis machinery of the cell can also be lethal. We have not discussed all of the possible ways that membranes can be damaged, such as direct injury by viruses, complement, channel blockers and ionophores. It should be apparent that damage to the cell's energy producing machinery and damage to the cell membrane are hopelessly intertwined.

The unifying concept is that no matter what the initial cause of cell injury, somewhere in the progression from normal steady-state to cell death, membrane disfunction, disruption of the cell's energy supply, or both lead to cell death.


Injury to cells relates to the health of the animal. How does cell injury result in a clinically ill or dying patient? Once we understand which organ or organs are failing, and how cells are being injured or killed, we may be able to intervene medically to reverse the process and restore the animal to health. Oxidative stress is associated with damage of proteins, lipids and nucleic acids, according to an article in the Pharmacognosy Review.

Several studies throughout the last few decades have suggested that oxidative stress plays a role in the development of many conditions, including macular degeneration, cardiovascular disease, certain cancers, emphysema, alcoholism, Alzheimer's disease, Parkinson's disease, ulcers and all inflammatory diseases, such as arthritis and lupus. Free radicals are also associated with aging.

Symptoms of oxidative stress

Free radicals can damage DNA's instructional code, causing our new cells to grow incorrectly, leading to aging. According to a article in Methods of Molecular Biology , there are no officially recognized symptoms of oxidative stress.

  • Lipid peroxidation.
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It is not possible to directly measure the amount of free radicals in the body, according to Rice University. According to a article in the American Journal of Clinical Nutrition , there are indirect methods of measuring oxidative stress, usually involving analysis of the byproducts of lipid peroxidation. The article warns that all methods should "should be used with caution because of the lack of accuracy, validity or both. The more recent article in Methods of Molecular Biology states that kits for testing oxidative stress are increasingly available, though their accuracy and validity are still under scrutiny.

Lipid peroxidation

Antioxidants keep free radicals in check. Antioxidants are molecules in cells that prevent free radicals from taking electrons and causing damage. Antioxidants are able to give an electron to a free radical without becoming destabilized themselves, thus stopping the free radical chain reaction.

Just like fiber cleans up waste products in the intestines, antioxidants clean up the free radical waste in the cells," said Wright. Well-known antioxidants include beta-carotene and other carotenoids, lutein, resveratrol, vitamin C, vitamin E, lycopene and other phytonutrients.

Our body produces some antioxidants on its own, but an insufficient amount. Oxidative stress occurs when there is an imbalance of free radicals and antioxidants too many free radicals and too few antioxidants , according to the Pharmacognosy Review. Antioxidants can be acquired through diet.

Antioxidants became well known in the s when scientists began to realize the possible effects of free radicals on cancer development, atherosclerosis and other chronic conditions. They also may have a link to aging, which has been defined as a gradual accumulation of free-radical damage, according to Christopher Wanjek, the Bad Medicine columnist for Live Science.

Fighting Free Radicals: Do You Need Antioxidants?

Substances that generate free radicals can be found in the food we eat, the medicines we take, the air we breathe and the water we drink, according to the Huntington's Outreach Project for Education at Stanford University. These substances include fried foods, alcohol, tobacco smoke, pesticides and air pollutants.

Free radicals are the natural byproducts of chemical processes, such as metabolism. Lauri Wright, a registered dietitian and an assistant professor of nutrition at the University of South Florida, said, "Basically, I think of free radicals as waste products from various chemical reactions in the cell that when built up, harm the cells of the body. Yet, free radicals are essential to life, Wanjek wrote in The body's ability to turn air and food into chemical energy depends on a chain reaction of free radicals.

Free radicals are also a crucial part of the immune system, floating through the veins and attacking foreign invaders. According to Rice University , once free radicals are formed, a chain reaction can occur.

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  5. The first free radical pulls an electron from a molecule, which destabilizes the molecule and turns it into a free radical. That molecule then takes an electron from another molecule, destabilizing it and tuning it into a free radical. This domino effect can eventually disrupt and damage the whole cell. The free radical chain reaction may lead to broken cell membranes, which can alter what enters and exits the cell, according to the Harvard School of Public Health. The chain reaction may change the structure of a lipid, making it more likely to become trapped in an artery. The damaged molecules may mutate and grow tumors.

    Or, the cascading damage may change DNA code. Oxidative stress occurs when there are too many free radicals and too much cellular damage. Oxidative stress is associated with damage of proteins, lipids and nucleic acids, according to an article in the Pharmacognosy Review.