About Free Radicals

By Jon Barron

What is a Free Radical?

A free radical is an especially reactive atom or group of atoms that has one or more unpaired electrons. If you remember your high school chemistry, you will remember that electrons come in pairs. When one electron is lost from that pair, it makes the atom “highly reactive” as it looks to replace that lost electron anywhere it can. In your body, those replacement electrons come from cells in your body–destroying those cells in the process. Free radicals put your body in a state of oxidative stress in which your body is no longer able to maintain a balance between the appearance of reactive oxygen species and its ability to detoxify those free radicals or to repair the resulting damage. That’s why free radicals function as cellular killers that wreak havoc by damaging DNA, altering biochemical compounds, corroding cell membranes, and destroying cells outright.

Another way to think of free radicals is as ravenous molecular sharks–sharks so hungry that in little more than a millionth of a second, they can be making a frenzied attack on a healthy neighboring cellular molecule. A single free radical can destroy an enzyme, a protein molecule, a strand of DNA, or an entire cell. Even worse, that one free radical can unleash, in a fraction of a second, a torrential chain reaction that produces a million or more additional killer free radicals–each out hunting for living cells to destroy like a herd of sharks in a mindless feeding frenzy.

Types of Free Radicals

There are different types of free radicals in the body. They each work in different areas of the body and on different cells or even different parts of cells. Four particularly destructive ones are:

  • Superoxide Radical. This radical tries to steal its much-needed electron from the mitochondria of the cell. When mitochondria are destroyed, the cell loses its ability to convert food to energy. It dies.
  • Hydroxyl radical. This free radical attacks enzymes, proteins, and the unsaturated fats in cell membranes.
  • Lipid Peroxyl Radical. This radical unleashes a chain reaction of chemical events that can so totally compromise the cellular membrane that the cell bursts open, spews its contents, and dies.
  • Singlet Oxygen. Not technically a free radical, this metabolite can nevertheless wreak havoc on the body. It’s listed here because it functions like a free radical and because it is controlled by antioxidants.

Free Radicals and Cancer

The connection between free radicals and cancer has been recognized for decades, but the underlying mechanisms have steadily become more apparent. For example, recently, it is becoming increasingly clear that metabolic oxidative free radical reactions are altered in cancer cells vs. normal cells. The current consensus is that cancer cells may exist in a chronic state of metabolic oxidative stress which may represent a significant underlying mechanism contributing to that cell’s malignancy. A unifying goal of the investigators in the Free Radical Cancer Biology Program, out of the University of Iowa Hospitals & Clinics, is to utilize a comprehensive understanding of redox biology to develop new biochemical techniques for improving cancer therapy by taking advantage of fundamental differences in the oxidative metabolism between cancerous cells and normal cells.


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