The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
All other sections in this Literature Study Guide are owned and copyrighted by BookRags, Inc.
The chemical compound quinone, or 1,4-benzoquinone, is a unicyclic, or ring phenolic compound. Quinone is a derivative of benzene, with two hydrogens replaced by two oxygens, each double bonded to a ring carbon (Figure 1). Quinone exists as yellow crystals, with a sharp odor similar to chlorine bleach. The chemical formula for quinone is C6H4O2, and its molecular weight is 108.1 grams per mole. Quinone is used as a chemical intermediate of complex reactions, an inhibitor of polymerization, a photographic chemical, an oxidizing agent, and a tanning agent. Benzoquinone and napthoquinone dyes also exist.
When a quinone cyclic molecule is the active portion of a larger molecule, it is referred to as being a quinone functional group. Quinone functional groups have powerful biological activity and are found in the most basic life-sustaining chemical reactions. For example, quinone functional groups are part of molecules perticipating in both cellular respiration and photosynthesis. Ubiquinone, or coenzyme Q, is a ubiquitous electron-shuttling molecule found in nearly all cells. Coenzyme Q is an essential electron and proton carrier that functions in the production of biochemical energy during respiration in aerobic organisms. It also has antioxidant and membrane stabilizing properties that serve to prevent the damage to cells by free radicals that results from normal metabolic processes. The structure of coenzyme Q consists of a quinone ring attached to a larger side chain molecule. Similarly, in photosynthesis, chlorophyll and the quinones are joined together by a protein and other molecules to form the photosynthetic reaction center, where energy from sunlight is converted into chemical energy.