free radical

free radical
Chem., Biochem.
an atom or molecule that bears an unpaired electron and is extremely reactive, capable of engaging in rapid chain reactions that destabilize other molecules and generate many more free radicals: in the body, deactivated by antioxidants, uric acid, and certain enzyme activities. Cf. diradical.
[1895-1900]

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Molecule containing at least one unpaired electron.

Most molecules contain even numbers of electrons, and their covalent bonds normally consist of shared electron pairs. Cleavage of such bonds produces two separate free radicals, each with an unpaired electron (in addition to any paired electrons). They may be electrically charged or neutral and are highly reactive and usually short-lived. They combine with one another or with atoms that have unpaired electrons. In reactions with intact molecules, they abstract a part to complete their own electronic structure, generating new radicals that go on to react with other molecules. Such chain reactions are particularly important in decomposition of substances at high temperatures and in polymerization. In the human body, oxidized (see oxidation-reduction) free radicals can damage tissues. Antioxidant nutrients (e.g., vitamin C, vitamin E, selenium) may reduce these effects. Heat, ultraviolet radiation, and ionizing radiation (see radiation injury) all generate free radicals. They are magnetic, so their properties can be studied with such techniques as magnetic susceptibility and electron paramagnetic resonance measurements.

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Universalium. 2010.

См. также в других словарях:

  • free radical — n technical an atom or group of atoms with at least one free ↑electron, which combines with other atoms very easily ▪ It is thought that free radicals can damage cells …   Dictionary of contemporary English

  • free radical — n an esp. reactive atom or group of atoms that has one or more unpaired electrons esp one that is produced in the body by natural biological processes or introduced from outside (as in tobacco smoke, toxins, or pollutants) and that can damage… …   Medical dictionary

  • free radical — noun count SCIENCE a molecule that has an extra ELECTRON and can react very easily with other molecules. Free radicals sometimes form in the human body and can cause cancer …   Usage of the words and phrases in modern English

  • free radical — n. an atom or molecule having at least one unpaired electron: free radicals are usually reactive and unstable …   English World dictionary

  • free radical — noun an atom or group of atoms with at least one unpaired electron; in the body it is usually an oxygen molecule that has lost an electron and will stabilize itself by stealing an electron from a nearby molecule (Freq. 2) in the body free… …   Useful english dictionary

  • free radical — UK / US noun [countable] Word forms free radical : singular free radical plural free radicals science a molecule that has an extra electron and can react very easily with other molecules. Free radicals sometimes form in the human body and can… …   English dictionary

  • free radical — laisvasis radikalas statusas T sritis fizika atitikmenys: angl. free radical vok. freies Radikal, n rus. свободный радикал, m pranc. radical libre, m …   Fizikos terminų žodynas

  • free radical — laisvasis radikalas statusas T sritis chemija apibrėžtis Atomas arba grupė, turinti orbitalę su nesuporuotu elektronu. atitikmenys: angl. free radical rus. свободный радикал …   Chemijos terminų aiškinamasis žodynas

  • free radical — free radicals N COUNT: usu pl Free radicals are atoms that contain one or more unpaired electrons. Free radicals are believed to be a cause of ageing, heart disease, and some cancers. [TECHNICAL] …   English dictionary

  • free radical — free′ rad′ical n. biochem. a molecular fragment that bears one or more unpaired electrons and is therefore highly reactive • Etymology: 1895–1900 …   From formal English to slang


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