Oxygen, chlorine, ozone, and peroxide compounds are
examples of oxidizing agents.
oxidoreductase An ENZYME of EC class 1, which
catalyzes an oxidation-reduction reaction.
oxygen One of the most important elements for bio-
logical systems and for other processes such as reacting
with other substances to release energy. One tree can
produce enough oxygen in one week to meet the
demands of a person’s daily oxygen need. Oxygen is
needed in oxidation-reduction reactions within cells.
Cellular respiration is the process that releases energy
by breaking down food molecules in the presence of
oxygen. Atomic symbol is O; atomic number is 8.
oxygen-evolving complex (OEC) The ENZYMEthat
catalyzes the formation of O 2 in PHOTOSYNTHESIS.
Contains a CLUSTERof probably four manganese ions.
ozone (O 3 ) A form of oxygen containing three
atoms instead of the common two formed by high-
energy ultraviolet radiation reacting with oxygen.
Ozone accounts for the distinctive odor of the air after
a thunderstorm or around electrical equipment, first
reported as early as 1785; ozone’s chemical constitu-
tion was established in 1872. The ozone layer in the
upper atmosphere blocks harmful ultraviolet radiation
that normally causes skin cancer. Ozone is an oxidizer
and disinfectant, and it forms hydrogen peroxide when
mixed with water. The Earth’s ozone layer protects all
life from the sun’s harmful radiation, but human activi-
ties have damaged this shield. The United States, in
cooperation with more than 140 other countries, is
phasing out the production of ozone-depleting sub-
stances in an effort to safeguard the ozone layer.
See alsoOXYGEN.ozonolysis The oxidation of an organic material by
ozone. The process of treating an organic compound
with ozone that splits a double bond in a hydrocarbon
chain and forms an ozonide (an unstable intermediate);
used to locate double bonds in molecules and to deter-
mine the structure of unsaturated fatty acids.206 oxidoreductase