T y p e s o f ch e m ica l re a ctio n s
All chemical reactions change reactants into products, but do so in different ways.
In our bodies, several processes can gener-
ate free radicals:
Exposure to ultraviolet radiation in sunlight
or to X-rays.
Some normal chemical reactions that occur
during metabolic processes.
Certain harmful substances, such as carbon
tetrachloride (a solvent used in dry cleaning).
Carbon tetrachloride can strip electrons away from other
molecules and produce free radicals.
The buildup of fatty ma-
terials in blood vessels.
stances that inactivate
Among the many disorders and diseases linked
to oxygen-derived free radicals are cancer,
, Alzheimer's disease, emphysema,
diabetes mellitus, cataracts, macular degener-
ation, rheumatoid arthritis, and deterioration
associated with aging. Consuming more
is thought to slow the pace of damage
caused by free radicals. Important dietary anti-
oxidants include selenium, zinc, beta-carotene,
and vitamins C and E. Red, blue, and purple fruits and
vegetables contain high levels of antioxidants.
30 CHAPTER 2