> What are free radicals?

Free radicals are oxygen atoms that are missing one electron from the pair the atom should have. When an atom is missing an electron from a pair, it becomes unstable and very reactive. That's because a free radical desperately wants to find another electron to fill in the gap, so it grabs an electron from the next atom it gets near.

The trouble is, when a free radical seizes an electron from another atom, the second atom then becomes a free radical, because now it's the one missing an electron. One free radical starts a cascade of new free radicals in our body. The free radicals blunder around, grabbing electrons from our cells-and doing a lot of damage to them at the same time.

Burning of fuel isn't the only thing that can make free radicals in our cells. Some other things include:

The ultraviolet light in sunshine - that's why people who spend too much time in the sun are more likely to get skin cancer and cataracts.

Toxins of all sort, such as: tobacco smoke, the natural chemicals found in our food, the poisonous wastes of our own metabolism, and man-made toxins like air pollution and pesticides.

On average, every cell in our body comes under attack from a free radical once every ten seconds.

Our best protection is to keep our antioxidant levels high.

If you want to understand a bit more about the way free radicals are made you can read the following section.

More on free radicals

To understand free radicals in more detail, we must first understand a bit about cells and molecules.

The body is made up of many different types of cell and cells are made of many different types of molecules. Molecules are made up of one or more atoms of one or more elements joined by chemical bonds and atoms consist of a nucleus, neutrons, protons and electrons.

The number of protons (positively charged particles) in the atom's nucleus determines the number of electrons (negatively charged particles) surrounding the atom.

Electrons are involved in chemical reactions and are the substance that bonds atoms together to form molecules. Electrons surround, or "orbit" an atom in one or more shells. The innermost shell is full when it has two electrons. When the first shell is full, electrons begin to fill the second shell. When the second shell has eight electrons, it is full, and so on.

The most important structural feature of an atom for determining its chemical behavior is the number of electrons in its outer shell. A substance that has a full outer shell tends not to enter into chemical reactions (it is an inert substance). Because atoms seek to reach a state of maximum stability, an atom will try to fill its outer shell by:

gaining or losing electrons to either fill or empty its outer shell, or

sharing its electrons by bonding together with other atoms in order to complete its outer shell.

Atoms often complete their outer shells by sharing electrons with other atoms. By sharing electrons, the atoms are bound together and satisfy the conditions of maximum stability for the molecule.

How are free radicals formed?

Normally, bonds don't split in a way that leaves a molecule with an odd, unpaired electron. But when weak bonds split, free radicals are formed. Free radicals are very unstable and react quickly with other compounds, trying to capture the needed electron to gain stability.

Generally, free radicals attack the nearest stable molecule, taking its electron. When the 'attacked' molecule loses its electron, it becomes a free radical itself, beginning a chain reaction. Once the process is started, it can continue, finally resulting in the disruption of a living cell.

Some free radicals arise normally during metabolism. Sometimes the body's immune system's cells purposefully create them to neutralize viruses and bacteria. However, environmental factors such as pollution, radiation, cigarette smoke and herbicides can also spawn free radicals.

Normally, the body can handle free radicals, but if antioxidants are unavailable, or if the free-radical production becomes excessive, damage can occur. Of particular importance is that free radical damage accumulates with age.

The chain reaction of free radical formation occurs in three stages:

1) Initiation - energy reactions cause the formation of the first free radicals:

2) Propagation - the chain reaction continues and various other free radicals form and become other substances; and

3) Termination - eventually an antioxidant is able to stop the chain reaction.

Free radicals in living cells

Free radicals are present in all living cell and are a part of the cell processes. However excessive free radicals in our cells can attack the cell membranes (the outer coat of the cell). This attack causes cell and tissue damage.

Radicals can also break strands of DNA (the genetic material in the cell). Some of the chemicals known to cause cancer, do so by forming free radicals.

Free-radical theory (Wikipedia)
http://en.wikipedia.org/wiki/Free-radical_theory