Biomaterial Database

Quinones as mediators of both artificial and cyclic phosphorylation in spinach chloroplasts. 1980

R G Binder, and B R Selman

A new method to prereduce mediators catalyzing cyclic electron transfer in washed, spinach thylakoid membranes was developed. Hydrophilic and lipophilic quinones were tested for their ability to catalyze phosphorylation in both cyclic electron transfer and electron transfer in an artificial transmembrane redox reaction. Quinones varied widely in their ability to catalyze cyclic photophosphorylation, but cyclic phosphorylation in all cases was inhibited by the plastoquinone antagonist dibromothymoquinone. Many of the quinones also catalyzed transmembrane electron transfer to ferricyanide trapped internally within the thylakoid vesicles. In this system, phosphorylation catalyzed by hydrophilic quinones was inhibited by dibromothymoquinone, whereas phosphorylation catalyzed by lipophilic quinones was dibromothymoquinone-insensitive. This is taken as evidence that transmembrane electron transfer catalyzed by hydrophilic quinones is mediated by the endogenous plastoquinone pool within the thylakoid membrane.

UI	MeSH Term	Description	Entries
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D010785	Photophosphorylation	The use of light to convert ADP to ATP without the concomitant reduction of dioxygen to water as occurs during OXIDATIVE PHOSPHORYLATION in MITOCHONDRIA.	Photosynthetic Phosphorylation,Phosphorylation, Photosynthetic,Phosphorylations, Photosynthetic,Photophosphorylations,Photosynthetic Phosphorylations
D010788	Photosynthesis	The synthesis by organisms of organic chemical compounds, especially carbohydrates, from carbon dioxide using energy obtained from light rather than from the oxidation of chemical compounds. Photosynthesis comprises two separate processes: the light reactions and the dark reactions. In higher plants; GREEN ALGAE; and CYANOBACTERIA; NADPH and ATP formed by the light reactions drive the dark reactions which result in the fixation of carbon dioxide. (from Oxford Dictionary of Biochemistry and Molecular Biology, 2001)	Calvin Cycle,Calvin-Benson Cycle,Calvin-Benson-Bassham Cycle,Carbon Fixation, Photosynthetic,Reductive Pentose Phosphate Cycle,Dark Reactions of Photosynthesis,Calvin Benson Bassham Cycle,Calvin Benson Cycle,Cycle, Calvin,Cycle, Calvin-Benson,Cycle, Calvin-Benson-Bassham,Photosynthesis Dark Reaction,Photosynthesis Dark Reactions,Photosynthetic Carbon Fixation
D010944	Plants	Multicellular, eukaryotic life forms of kingdom Plantae. Plants acquired chloroplasts by direct endosymbiosis of CYANOBACTERIA. They are characterized by a mainly photosynthetic mode of nutrition; essentially unlimited growth at localized regions of cell divisions (MERISTEMS); cellulose within cells providing rigidity; the absence of organs of locomotion; absence of nervous and sensory systems; and an alternation of haploid and diploid generations. It is a non-taxonomical term most often referring to LAND PLANTS. In broad sense it includes RHODOPHYTA and GLAUCOPHYTA along with VIRIDIPLANTAE.	Plant
D011809	Quinones	Hydrocarbon rings which contain two ketone moieties in any position. They can be substituted in any position except at the ketone groups.
D002736	Chloroplasts	Plant cell inclusion bodies that contain the photosynthetic pigment CHLOROPHYLL, which is associated with the membrane of THYLAKOIDS. Chloroplasts occur in cells of leaves and young stems of plants. They are also found in some forms of PHYTOPLANKTON such as HAPTOPHYTA; DINOFLAGELLATES; DIATOMS; and CRYPTOPHYTA.	Chloroplast,Etioplasts,Etioplast
D004227	Dithionite	Dithionite. The dithionous acid ion and its salts.	Hyposulfite,Sodium Dithionite,Dithionite, Sodium
D013329	Structure-Activity Relationship	The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.	Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships