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Free Radical Theory

• During aging, damage produced by free radicals

cause cells and organs to stop functioning.

•

The free radical theory of aging was conceivedby Denham Harman in the 1950s, when prevailing

scientific opinion held that free radicals were too

unstable to exist in biological systems, and before

anybody had invoked free radicals as a cause of degenerative diseases.

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Free Radical Theory

The free radical “grabs” a electron from any

molecule it its vicinity.

It does this because electrons like to exist inpairs.

When it “grabs” an electron from anothermolecule, it damages the other molecule.

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Free Radical Theory

• Some of the molecules that may be damaged by freeradicals are fats, proteins, and DNA (both in thenucleus and in mitochondria).

• If membrane fats are attacked, then you get thebreakdown of the cell membrane. If it is a red bloodcell membrane, you get hemolysis.

• If proteins are attacked, you get the breakdown of proteins, which may result in the loss of biological

function and the accumulation of “catastrophic”compounds.

• If DNA is attacked, you will get a mutation that maycause aging or cancer.

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 Free Radicals

As the free radical (green) attacks the membrane it

can release another type free radical (blue).

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Damaged membrane

The free radical (blue) attacks the DNA releasing another

free radical (purple).

mitochondrion

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Free Radical Theory

• Free radicals do not go unchecked. The body has a

multi-layed defense system that reacts and detoxifies

the damaging radicals.

• Defenses include: – Natural antioxidants in the body, such as bilirubin.

 – Enzymes such as superoxide dismutase (SOD), catalase, &

glutathione peroxidase.

 – Dietary antioxidants such as beta carotene, and the

vitamins C and E.

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Free Radical Theory

• Under normal conditions, your naturaldefense mechanisms prevent most of theoxidative damage from occurring.

• The free radical theory of aging proposes that,little-by-little, small amounts of damage

accumulate and contribute to deterioration of tissues and organs.

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anti-oxidant

molecule

repaired

membranedamaged

DNA

The anti-oxidant molecule destroys the damaging free radical. Themembrane repairs itself, but the DNA remains damaged, impairing the

cells function. In addition, the anti-oxidant molecule now has an

unpaired electron and thus becomes a new radical.

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Free Radical Theory

For example, when Vitamin E “scavenges” free

radicals, it becomes a free radical and may be more

carcinogenic than the original free radical.

This is the reason why taking high doses of vitamin E

SUPPLEMENTS appears to INCREASE cancer risk in aperson, not decrease cancer risk.

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Free Radical Theory

• Not all free radicals cause damage.

• You use free radicals as part of your immunologicalresponse system.

 –

Macrophages engulf bacteria – Free radical reactions produced inside the macrophage

oxidize and kill bacteria.

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