Refleks va uning turlari Reja Oliy nerv faoliyatini o’rganishda I. M. Sechenovning «Bosh miya reflekslari»

is only possible because of the high reactivity of oxygen. The same
process may create other reactive forms of oxygen that are not radicals
(e. g., hydrogen peroxide), some of which are even more reactive and so
aggressive that they can extract electrons from other molecules. The result
is new radicals that oxidize other molecules as they try to become
stabilized, producing damage to cellular structures:
_ Damage to DNA in the chromosomes may entail mutations in the
genes or uncontrolled cell division (cellular degeneration or cancer
production).
_ Oxidized LDL (see Chapter 6: Plasma Proteins) in the blood are
deposited preferentially in damaged vascular walls (arteriosclerosis);
antioxidants prevent the oxidation.
_ Cell membranes are damaged when fatty acids in phospholipids are
oxidized to peroxides (peroxidation of lipids). Premature senility may
ensue (increased cell death, deposition of the products of oxidation).
Antioxidants protect the cell membrane from oxidation and so prevent
death of the cell or impairment of cellular function by the products
of oxidation.
Extreme physical exertion and acute inflammation, as well as products
that damage the environment (e. g., ozone, nitric oxide) and ultraviolet
and radioactive radiation, lead to increased formation of free radicals
during cell metabolism (oxidative stress).
Active Substances in Plants
As well as vitamins, minerals, trace elements, and fiber, fruit and vegetables
contain a number of substances that protect them from dangerous