Biomaterial Database

Catechols stimulate ferricyanide reduction in chloroplast photosystem II. 1979

R Barr, and F L Crane

In isolated chloroplasts (Spinacia olearacea), where electron transport to Photosystem I is blocked by the plastoquinone antagonist, dibromothymoquinone, lipophilic catechols in concentrations of 50--150 microM stimulate ferricyanide reduction in Photosystem II and associated O2 evolution. Non-permeating catechols, such as Tiron, are unable to stimulate this reaction. Those quinones, such as 2,5-dimethylbenzoquinone, which act as class III electron acceptors, do not lead to stimulation of ferricyanide reduction in Photosystem II or stimulation fo associatied O2 evolution, when electron transport to Photosystem I is blocked by dibromoquinone. Stimulation of ferricyanide reduction is not observed in Tris-treated chloroplasts, implying that electron donation to Photosystem II by catechols is not responsible for the stimulation. Various mechanisms for this stimulation in class II chloroplasts are discussed.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
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
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
D011794	Quercetin	A flavonol widely distributed in plants. It is an antioxidant, like many other phenolic heterocyclic compounds. Glycosylated forms include RUTIN and quercetrin.	3,3',4',5,7-Pentahydroxyflavone,Dikvertin
D002396	Catechols	A group of 1,2-benzenediols that contain the general formula R-C6H5O2.	Pyrocatechols,o-Dihydroxybenzenes,ortho-Dihydroxybenzenes,o Dihydroxybenzenes,ortho Dihydroxybenzenes
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
D003374	Coumarins	Synthetic or naturally occurring substances related to coumarin, the delta-lactone of coumarinic acid.	1,2-Benzopyrone Derivatives,1,2-Benzopyrones,Coumarin Derivative,Coumarine,1,2-Benzo-Pyrones,Benzopyran-2-ones,Coumarin Derivatives,Coumarines,1,2 Benzo Pyrones,1,2 Benzopyrone Derivatives,1,2 Benzopyrones,Benzopyran 2 ones,Derivative, Coumarin,Derivatives, 1,2-Benzopyrone,Derivatives, Coumarin
D005292	Ferricyanides	Inorganic salts of the hypothetical acid, H3Fe(CN)6.
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