Carbon dioxide fixation chloroplasts

Ozone causes both quantitative and qualitative changes in carbon dioxide fixation patterns. Wilkinson and Bames, using carbon dioxide-found a reduction in radioactivity in soluble sugars and increases in free amino acids and sugar phosphates in white pine after a 10-min exposure to ozone at 0.10 ppm. Miller observed a decrease in carbon dioxide-fixation in ponderosa pines that correlated with loss of chlorophyll, after exposure to ozone at 0.30-0.35 ppm. The Hill reaction rates of chloroplasts isolated from healthy and ozone-injured ponderosa pine indicated that both light and dark reactions of the chloroplasts from ozone-injured plants were depressed. Barnes found depressed photosynthesis and stimulated respiration in seedlings of four pine species of the southeastern United States after exposure to ozone at 0.15 ppm. 

These are involved in a wide range of electron-transfer processes and in certain oxidation-reduction enzymes, whose function is central to such important processes as the nitrogen cycle, photosynthesis, electron transfer in mitochondria and carbon dioxide fixation. The iron-sulfur proteins display a wide range of redox potentials, from +350 mV in photosynthetic bacteria to —600 mV in chloroplasts. 

Chloroplasts of higher plants are saucer-shaped, and from 4 to 10 ym in diameter and 1 to 3 ym thick. The chlorophyll is concentrated in bodies within the chloroplasts called grana, which are about 0.4 ym in diameter. Under the electron microscope, the grana appear as highly organized, precisely stacked lamellae, to which the chlorophyll is bound, imbedded in a stroma matrix. The light and associated electron transport reactions take place in the lamellae, whereas enzymes involved in carbon dioxide fixation are located in the stroma. 

Where does carbon dioxide fixation take place in the cell The chloroplast has a highly organized structure. How does this structure help make photosynthesis possible ... 

Karube I, Aizawa K, Ikeda S et al. Carbon dioxide fixation by immobilized chloroplasts. Biotechnol Bioeng 1979 21 253-260. 

Catharanthus roseus, Digitata lanata, and Morinda citrifolia plant cells have been immobilized in calcium alginate gels and applied to the production and transformation of natural products.Chloroplasts of Brassica campestris L copolymerized with acrylamide have been used to investigate carbon dioxide fixation by the immobilized cells, whose fixation activity was 65% that of free cells but which were more stable than free cells to alkaline conditions and high temperature. 

Study of carbon dioxide fixation by the living immobilized cells Study of properties of active immobilized chloroplasts... 

Superoxide radicals are inevitably photoproduced in chloroplasts, and hydrogen peroxide is formed from superoxide. Hydrogen peroxide not only inhibits the enzymes for the cycle of carbon dioxide fixation, but also produces the hydroxyl radical by metal-catalyzed Haber-Weiss reaction (1). AsA peroxidase takes an important part in scavenging hydrogen peroxide in chloroplasts (1), which lack catalase and glutathione peroxidase (2). We have purified two types of AsA peroxidase from tea leaves (3), and one of them (isoz3nne II) is localized in chloroplasts (4, Chen and Asada, unpublished). 

Arnon and his collaborators (11,15) have reported that whole spinach chloroplasts, prepared in 0.5 M glucose or 0.35 M NaCl, are able to carry out not only the Hill reaction (f.c., the photolysis of water in the presence of artificial hydrogen acceptors) but also photosynthetic phosphorylation and carbon dioxide fixation. Both these processes are light-dependent and strongly inhibited by o-phenanthroline, which interferes with the photochemical reaction. Their early results are shown in Table V. These important findings... 

The isolation of chloroplasts capable of performing all of the reactions normally regarded as photosynthetic including the fixation of carbon dioxide, the evolution of oxygen and the synthesis of sugars and polysaccharides unequivocally demonstrates that the site of photosynthesis is the chloroplast. Experiments involving the fractionation of chloroplasts have further shown that the dark reactions associated with carbon dioxide fixation are located in the stroma of the chloroplast and the light reactions , electron transport and photophosphorylation, takes place in the lamellar systems. 

Chloroplasts in plant cells are surrounded by a double membrane and have an internal membrane system of thylakoid vesicles that are stacked up to form grana. The thylakoid vesicles contain chlorophyll and are the site of photosynthesis. Carbon dioxide (C02) fixation takes place in the stroma, the soluble matter around the thylakoid vesicles. 

Calvin cycle (aka Calvin-Benson Cycle or Carbon Fixation) Series of biochemical, enzyme-mediated reactions during which atmospheric carbon dioxide is reduced and incorporated into organic molecules, eventually some of this forms sugars. In eukaryotes, this occurs in the stroma of the chloroplast. 

As a result, oxaloacetate (OAA, C4-compound) is formed unlike the case of the Calvin-Benson cycle in which 3-phosphoglycerate (C3-compound) is formed. The pathway in the fixation of carbon dioxide by the catalysis of PEP-carboxylase is observed in sugar cane, corn, etc., and is called the Hatch-Slack pathway (Hatch et al., 1967). The plants having the Hatch-Slack pathway have chloroplasts both in mesophyll cells and in vascular bundle sheath cells, and the Hatch-Slack pathway occurs in the mesophyll cells. Oxaloacetate formed by the fixation of carbon dioxide in the mesophyll cells is reduced to malate. Malate thus formed moves to the vascular bundle sheath cells and releases carbon dioxide there. Carbon dioxide released is fixed by the catalysis of Rubisco, and the organic compounds are formed through the Calvin-Benson cycle. (Fig. 6.3). 

Robert Hill demonstrated in 1937 that the oxidation of H2O to O2 and CO2 fixation into carbohydrates are separate processes (Hill 1937). He observed O2 evolution by chloroplast suspensions when artificial electron acceptors, other than CO2, are used. This reaction, which Hill called the chloroplast reaction , later became known as the ""Hill reaction . This, and the postulate of Warburg that the fixation of carbon dioxide is energy consuming but independent of hght, was confirmed by Ruben, Kamen and his coworkers in 1939-1941 after the isotope technique had found its way to biochemistry (Ruben 1939, Ruben et al. 1941). In 1945 Melvin Calvin commenced research to determine the pathway by which CO2 becomes fixed into carbohydrate. 

The specific rate of sugar production in the chloroplast q thus is a direct measure of the rate of photosynthesis and is equivalent to the specific rate of oxygen (O2) production or carbon dioxide (CO2) fixation, which are also used as measures of photosynthesis. The superscript c is used to denote that these reactions take place in the chloroplast. 

Within the research arena of the higher plants (crop plants) much more work has been done on resolving the spectral dependency of the efficiency oflight use in photosynthesis (Evans, 1987 McCree, 1971). The most recent study is the one of Hogewoning et al (2012) who measured the maximal yield of carbon dioxide (CO2) fixation in cucumber leaves as a function of wavelength. CO2 frxation in the chloroplasts is equivalent to sugar... 

Vishniac, W. and Ochoa, S. (1953) Fixation of carbon dioxide coupled to photochemical reduction of pyridine nucleotides by chloroplast preparations. J. Biol. Chem. 195, 75-93. 

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