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Phaeophytin
Pheophytin or phaeophytin is a chemical compound that serves as the first electron carrier intermediate in the electron transfer pathway of Photosystem II (PS II) in plants, and the type II photosynthetic reaction center (RC P870) found in purple bacteria. In both PS II and RC P870, light drives electrons from the reaction center through pheophytin, which then passes the electrons to a quinone (QA) in RC P870 and RC P680. The overall mechanisms, roles, and purposes of the pheophytin molecules in the two transport chains are analogous to each other. Structure In biochemical terms, pheophytin is a chlorophyll molecule lacking a central Mg2+ ion. It can be produced from chlorophyll by treatment with a weak acid, producing a dark bluish waxy pigment. The probable etymology comes from this description, with ''pheo'' meaning ''dusky'' and ''phyt'' meaning ''vegetation''. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosynthetic Pigments
A photosynthetic pigment (accessory pigment; chloroplast pigment; antenna pigment) is a pigment that is present in chloroplasts or photosynthetic bacteria and captures the light energy necessary for photosynthesis. List of photosynthetic pigments (in order of increasing polarity): *Carotene: an orange pigment *Xanthophyll: a yellow pigment * Phaeophytin ''a'':CHLOROPHYLLS JECFA, 1987 a gray-brown pigment * Phaeophytin ''b'': a yellow-brown pigment * Chlorophyll ''a'': a blue-green pigment * Chlorophyll ''b'': a yellow-gr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phaeophytin A
Pheophytin or phaeophytin is a chemical compound that serves as the first electron carrier intermediate in the electron transfer pathway of Photosystem II (PS II) in plants, and the type II photosynthetic reaction center (RC P870) found in purple bacteria. In both PS II and RC P870, light drives electrons from the reaction center through pheophytin, which then passes the electrons to a quinone (QA) in RC P870 and RC P680. The overall mechanisms, roles, and purposes of the pheophytin molecules in the two transport chains are analogous to each other. Structure In biochemical terms, pheophytin is a chlorophyll molecule lacking a central Mg2+ ion. It can be produced from chlorophyll by treatment with a weak acid, producing a dark bluish waxy pigment. The probable etymology comes from this description, with ''pheo'' meaning ''dusky'' and ''phyt'' meaning ''vegetation''. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Carrier
An electron transport chain (ETC) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. The electrons that transferred from NADH and FADH2 to the ETC involves 4 multi-subunit large enzymes complexes and 2 mobile electron carriers. Many of the enzymes in the electron transport chain are membrane-bound. The flow of electrons through the electron transport chain is an exergonic process. The energy from the redox reactions creates an electrochemical proton gradient that drives the synthesis of adenosine triphosphate (ATP). In aerobic respiration, the flow of electrons terminates with molecular oxygen as the final electron acceptor. In anaerobic respiration, other electron acceptors are used, such as sulfate. In an electron transport chain, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
P680
P680, or photosystem II primary donor, is the reaction-center chlorophyll ''a'' molecular dimer associated with photosystem II in plants, algae, and cyanobacteria, and central to oxygenic photosynthesis. Etymology Its name is derived from the word “pigment” (P) and the presence of a major bleaching band centered around 680-685 nm in the flash-induced absorbance difference spectra of P680/ P680+•.Shigeru Itoh, S; Iwaki, M; Tomo, T; Satoh, K (1996). Dibromothymoquinone (DBMIB) replaces the function of QA at 77 K in the isolated photosystem II reaction center (Dl-D2-cytochrome 6559) complex: Difference spectrum of the P680+ (DBMIB") state. Plant Cell Physiol. 37(6): 833-839. Components The structure of P680 consists of a heterodimer of two distinct chlorophyll molecules, referred to as P and P. This “special pair” forms an excitonic dimer that functions as a single unit, excited by light energy as if they were a single molecule. Action and function Excitatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorophyllide
Chlorophyllide ''a'' and Chlorophyllide ''b'' are the biosynthetic precursors of chlorophyll ''a'' and chlorophyll ''b'' respectively. Their propionic acid groups are converted to phytyl esters by the enzyme chlorophyll synthase in the final step of the pathway. Thus the main interest in these chemical compounds has been in the study of chlorophyll biosynthesis in plants, algae and cyanobacteria. Chlorophyllide ''a'' is also an intermediate in the biosynthesis of bacteriochlorophylls. Structures Chlorophyllide ''a'', is a carboxylic acid (R=H). In chlorophyllide ''b'', the methyl group at position 13 ( IUPAC numbering for chlorophyllide ''a'') and highlighted in the green box, is replaced with a formyl group. Biosynthesis steps up to formation of protoporphyrin IX In the early steps of the biosynthesis, which starts from glutamic acid, a tetrapyrrole is created by the enzymes deaminase and cosynthetase which transform aminolevulinic acid via porphobilinogen and hydro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction Center
A photosynthetic reaction center is a complex of several proteins, pigments and other co-factors that together execute the primary energy conversion reactions of photosynthesis. Molecular excitations, either originating directly from sunlight or transferred as excitation energy via light-harvesting antenna systems, give rise to electron transfer reactions along the path of a series of protein-bound co-factors. These co-factors are light-absorbing molecules (also named chromophores or pigments) such as chlorophyll and pheophytin, as well as quinones. The energy of the photon is used to excite an electron of a pigment. The free energy created is then used, via a chain of nearby electron acceptors, for a transfer of hydrogen atoms (as protons and electrons) from H2O or hydrogen sulfide towards carbon dioxide, eventually producing glucose. These electron transfer steps ultimately result in the conversion of the energy of photons to chemical energy. Transforming light energy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorophyll
Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to absorb energy from light. Chlorophylls absorb light most strongly in the blue portion of the electromagnetic spectrum as well as the red portion. Conversely, it is a poor absorber of green and near-green portions of the spectrum. Hence chlorophyll-containing tissues appear green because green light, diffusively reflected by structures like cell walls, is less absorbed. Two types of chlorophyll exist in the photosystems of green plants: chlorophyll ''a'' and ''b''. History Chlorophyll was first isolated and named by Joseph Bienaimé Caventou and Pierre Joseph Pelletier in 1817. The presence of magnesium in chlorophyll was discovered in 1906, and was that element's first detection in living tissue. After initial work done by German ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosystem
Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII. PSII will absorb red light, and PSI will absorb far-red light. Although photosynthetic activity will be detected when the photosystems are exposed to either red or far-red light, the photosynthetic activity will be the greatest when plants are exposed to both wavelengths of light. Studies have actually demonstrated that the two wavelengths together have a synergistic effect on the photosynthetic activity, rather than an additive one. Each photosystem has two parts: a reaction center, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored in carbohydrate molecules, such as sugars and starches, which are synthesized from carbon dioxide and water – hence the name ''photosynthesis'', from the Greek ''phōs'' (), "light", and ''synthesis'' (), "putting together". Most plants, algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies most of the energy necessary for life on Earth. Although photosynthesis is performed differently by different species, the process always begins when energy from light is absorbed by proteins called reaction centers that contain green chlorophyll (and other colored) pigments/chromoph ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cytochrome
Cytochromes are redox-active proteins containing a heme, with a central Fe atom at its core, as a cofactor. They are involved in electron transport chain and redox catalysis. They are classified according to the type of heme and its mode of binding. Four varieties are recognized by the International Union of Biochemistry and Molecular Biology (IUBMB), cytochromes a, cytochromes b, cytochromes c and cytochrome d. Cytochrome function is linked to the reversible redox change from ferrous (Fe(II)) to the ferric (Fe(III)) oxidation state of the iron found in the heme core. In addition to the classification by the IUBMB into four cytochrome classes, several additional classifications such as cytochrome o and cytochrome P450 can be found in biochemical literature. History Cytochromes were initially described in 1884 by Charles Alexander MacMunn as respiratory pigments (myohematin or histohematin). In the 1920s, Keilin rediscovered these respiratory pigments and named them the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photosystem2
Photosystems are functional and structural units of protein complexes involved in photosynthesis. Together they carry out the primary photochemistry of photosynthesis: the absorption of light and the transfer of energy and electrons. Photosystems are found in the thylakoid membranes of plants, algae, and cyanobacteria. These membranes are located inside the chloroplasts of plants and algae, and in the cytoplasmic membrane of photosynthetic bacteria. There are two kinds of photosystems: PSI and PSII. PSII will absorb red light, and PSI will absorb far-red light. Although photosynthetic activity will be detected when the photosystems are exposed to either red or far-red light, the photosynthetic activity will be the greatest when plants are exposed to both wavelengths of light. Studies have actually demonstrated that the two wavelengths together have a synergistic effect on the photosynthetic activity, rather than an additive one. Each photosystem has two parts: a reaction center, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteriochlorophylls
Bacteriochlorophylls (BChl) are photosynthetic pigments that occur in various phototrophic bacteria. They were discovered by C. B. van Niel in 1932. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanobacteria. Organisms that contain bacteriochlorophyll conduct photosynthesis to sustain their energy requirements, but do not produce oxygen as a byproduct. They use wavelengths of light not absorbed by plants or cyanobacteria. Replacement of with protons gives bacteriophaeophytin (BPh), the phaeophytin form. BacterioChlorophyll a.svg, bacteriochlorophyll ''a'' BacterioChlorophyll b.svg, bacteriochlorophyll ''b'' BacterioChlorophyll c.svg, bacteriochlorophyll ''c'' BacterioChlorophyll d.svg, bacteriochlorophyll ''d'' BacterioChlorophyll e.svg, bacteriochlorophyll ''e'' Bacteriochlorophyll f.svg, bacteriochlorophyll ''f'' BacterioChlorophyll g.svg, bacteriochlorophyll ''g'' Structure Bacteriochlorophylls ''a'', ''b'', and ''g'' are ba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
