ubiquinone

u·bi·qui·none

U0001550 (yo͞o′bĭ-kwĭ-nōn′, -kwĭn′ōn′)n. Any of a family of fat-soluble quinone compounds that are found in the membranes of eukaryotic cells, especially in mitochondria, and serve as electron carriers in cellular respiration and other processes. Also called coenzyme Q.

[Blend of ubiquitous (from its widespread distribution) and quinone.]

ubiquinone

(juːˈbɪkwɪˌnəʊn) n (Biochemistry) another name for coenzyme Q

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Noun

ubiquinone - any of several quinones found in living cells and that function as coenzymes that transfer electrons from one molecule to another in cell respirationcoenzyme Qbiochemistry - the organic chemistry of compounds and processes occurring in organisms; the effort to understand biology within the context of chemistrycoenzyme - a small molecule (not a protein but sometimes a vitamin) essential for the activity of some enzymesbenzoquinone, quinone - any of a class of aromatic yellow compounds including several that are biologically important as coenzymes or acceptors or vitamins; used in making dyes

Ubiquinone

(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 UQ_n or CoQ_n; 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, UQ_30–50 in fungi, UQ₄₀ in bacteria, UQ_40–45 in protozoa, and UQ_45–50 in insects. Plant mitochondria contain UQ_40–50 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.

REFERENCES

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.

V. V. ZUEVSKII

ubiquinone

coenzyme

[ko-en´zīm] an organic molecule, usually containing phosphorus and some vitamins, sometimes separable from the enzyme protein; a coenzyme and an apoenzyme must unite in order to function (as a holoenzyme).coenzyme A a coenzyme essential for carbohydrate and fat metabolism; among its constituents are pantothenic acid and a terminal SH group, which forms linkages with various acids, e.g., acetic acid (acetyl CoA) and fatty acids (acyl CoA); abbreviated CoA.coenzyme Q any of a group of related quinones occurring in the lipid fraction of mitochondria and serving, along with the cytochromes, as an intermediate in electron transport; they are similar in structure and function to vitamin K₁.

u·bi·qui·none

(ū'bi-kwī'nōn, ū-bik'wi-nōn), A 2,3-dimethoxy-5-methyl-1,4-benzoquinone with a multiprenyl side chain; a mobile component of electron transport.
See also: coenzyme Q.

ubiquinone

(yo͞o′bĭ-kwĭ-nōn′, -kwĭn′ōn′)n. A quinone compound that serves as an electron carrier between flavoproteins and in cellular respiration.

coenzyme Q10

A factor present in mitochondria which extracts energy from foods. It has acquired a reputation among fringe nutritionists as being effective in detoxifying patients with an overdose of environmental pollutants; it is also claimed to be beneficial in treating hypertension, obesity, periodontal disease, preventing cancer, increasing longevity and revitalising the immune system.

u·bi·qui·none

(yū'bi-kwi'nōn) A 2,3-dimethoxy-5-methyl-1,4-benzoquinone with a multiprenyl side chain; a mobile component of electron transport.
See also: coenzyme Q

ubiquinone

coenzyme Q

a type of QUINONE that can be reversibly reduced. It functions as an electron carrier in ELECTRON TRANSPORT SYSTEMS.

ubiquinone

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ubiquinone

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REFERENCES

ubiquinone

coenzyme

u·bi·qui·none

ubiquinone

coenzyme Q10

u·bi·qui·none

ubiquinone

coenzyme Q

ubiquinone

Synonyms for ubiquinone

noun any of several quinones found in living cells and that function as coenzymes that transfer electrons from one molecule to another in cell respiration

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