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.
Photophosphorylation is the light powered production of energy-rich adenosine triphosphate (ATP) during photosynthesis. ATP is formed by phosphorylation of adenosine diphosphate (ADP) in a reaction that stores energy in the bond linking ADP with an added phosphoryl group. Light provides the needed energy and in the process is converted into chemical energy. The chemical energy stored in ATP is used to synthesize sugars and other biochemical products of photosynthesis. In green plants the process takes place in a plant organelle called the chloroplast. The primary light-absorbing pigment is called chlorophyll, and is the substance responsible for the plant's green color. Based on the type of electron flow involved there are two types of photophosphorylation, cyclic and non-cyclic. In cyclic photophosphorylation the electron associated with a chlorophyll molecule is excited by a light photon but than returns to the original chlorophyll molecule from which it was emitted, whereas in the non-cyclic process electrons are transferred from an emitting to an accepting chlorophyll molecule. In either case, intermediate electron carriers mediate the flow and capture the energy lost by the electron in returning to an unexcited state. The intricate energy conversion process requires a precise structural organization of thylakoid membranes in the interior of the chloroplast to successfully couple electron flow to the ATP producing process. Any disruption of the elaborate thylakoid structure leads to an uncoupling of electron flow from ATP production, and photosynthesis is no longer possible.