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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(also benzoquinone, coenzyme Q), any of a series of derivatives of 5-methyl-2,3-dimethoxyquinone having a variable terpenoid side chain attached to the carbon atom in position six. Ubiquinones have from six to ten isoprenoid units (C5H8). The structural formula is

Ubiquinones figure in reactions that supply energy to cells. They are designated by the symbols UQn or CoQn; in the first, n represents the number of carbon atoms, and in the second, the number of isoprenoid units. For example, UQ30 will correspond to CoQ6. Ubiquinones occur as colorless, crystalline substances whose absorption maximum is at 270 micrometers. They are insoluble in water and soluble in organic solvents.

Ubiquinones are present in all organisms; UQ50 predominates in mammals, UQ30–50 in fungi, UQ40 in bacteria, UQ40–45 in protozoa, and UQ45–50 in insects. Plant mitochondria contain UQ40–50 in small quantities, and the chloroplasts in plants contain plastoquinones, which are similar to ubiquinones. Various naph-thoquinones occur in certain bacteria.

The biological role of ubiquinones is based on their ability to participate in reversible oxidation-reduction conversions. Ubiquinones are located in the cytoplasmic membranes of bacteria and in the inner membranes of mitochondria. They participate in the transfer of electrons and hydrogen between flavoproteins and cytochrome b in the respiratory chain.


Skulachev, V. P. Transformatsiia energii v biomembranakh. Moscow, 1972.
Morton, R. A. “Ubiquinones, Plastoquinones, and Vitamins K.” Biological Reviews of the Cambridge Philosophical Society, 1971, vol. 46, no. 1.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
A mitochondrial-targeted ubiquinone modulates muscle lipid profile and improves mitochondrial respiration in obesogenic diet-fed rats.
Coulter et al., "Selective targeting of a redox-active ubiquinone to mitochondria within cells: antioxidant and antiapoptotic properties," The Journal of Biological Chemistry, vol.
Caption: Figure 2: Mitochondria-targeted antioxidants with ubiquinone or plastoquinone antioxidant moiety, that are used in kidney ischemia/reperfusion injury.
Farnesol, nerolidol, and linalool showed stronger inhibitory activity in the biosynthesis of the isoprenic side chain of the benzoquinone ring of ubiquinones in the schizont stage.
Novoselova, "The role of ubiquinones in the regulation of lipid metabolism in rat thymocytes," FEBS Letters, vol.
The endogenous ubiquinones play a key role in one-electron transfers in the mitochondrial inner membrane as well as PTP transition (Fontaine et al.
should be shifted to the left in case of ubiquinone and to the right in case of plastoquinone, in agreement with our observations and also the earlier reports on the long life of pulse-generated ubiquinone radicals in the presence of oxygen [117, 119].
Kucharska et al., "Increased ubiquinone concentration after intracerebroventricularly administered ubiquinol to selected rat brain regions," General Physiology and Biophysics, vol.
Determination of reduced and total ubiquinones in biological materials by liquid chromatography with electrochemical detection.
One of the main functions of complex I is the transport of electrons across the inner mitochondrial membrane via the oxidation of NADH coupled to reduction of ubiquinone (2).