Xem 1-20 trên 76 kết quả Metabolic reactions
  • A global research community of scientists is teasing out the biochemical mechanisms that regulate normal cellular physiology in a variety of organisms. Much of current research aims to understand the network of molecular reactions that regulate cellular homeostasis, and to learn what allows cells to sense stress and activate appropriate biochemical responses.

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  • Fatty acids are an important energy source, for they yield over twice as much energy as an equal mass of carbohydrate or protein. In humans, the primary dietary source of fatty acids is triacylglycerols. This lecture will describe the metabolism of fatty acids. The two main components of fatty acid metabolism are β oxidation and fatty acid synthesis. Upon completion of this lecture, you will understand that the fatty-acid breakdown reactions of β oxidation result in the formation of reduced cofactors and acetyl-CoA molecules, which can be further catabolized to release free energy.

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  • Methionine (Met) is an essential amino acid and the only sub-strate for synthesis of S-adenosylmethionine (AdoMet) that is the main substrate for multiple intracellular methylases. There are two modes of Met metabolism in liver. In case of its dietary restriction Met can be metabolized via conservative remethylation cycle. In case of Met excess (high [Met]) it is mostly converted to cysteine via transsulfuration pathway.

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  • Nowadays, with over a thousand bacterial genomes sequenced, even greater opportunities have opened for experimental or computational global analysis of metabolism, physiology, and evolution. In particular, the access to comprehensive sets of molecular components (genes, proteins, regulatory signals) is at the basis of the development of novel integrative approaches, aiming at understanding the function of specific sets of these components (operons, regulons, metabolic pathways, protein complexes, etc.) in the context of the whole organism.

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  • Cytochrome P450 monooxygenases (P450s) are a diverse collection of enzymes acting on various endogenous and xenobiotic molecules. Most of them catalyse hydroxylation reactions and one group of possible substrates are fatty acids and their related structures. In this minireview, the signifi-cance of P450s in microbial fatty acid conversion is described.

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  • Several bacteria, including Azotobacter vinelandii, possess an alternative pathway ofl-rhamnose metabolism, which is different from the known bacterial pathway. In a previous article, a gene cluster related to this path-way was identified, consisting of the genes encoding the four metabolic enzymes l-rhamnose-1-dehydrogenase (LRA1), l-rhamnono-c-lactonase (LRA2),

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  • The control properties of biochemical pathways can be described by control coefficients and elasticities, as defined in the framework of metabolic control analysis. The determination of these parameters using the traditional metabolic control analysis relationships is, however, lim-ited by experimental difficulties (e.g. realizing and meas-uring small changes in biological systems) and lack of appropriate mathematical procedures (e.g. when the more practical large changes are made).

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  • Amino acid biosynthesis and central carbon metabolism of Pichia pastoriswere studied using biosynthetically directed fractional 13 C labeling. Cells were grown aerobically in a chemostat culture fed at two dilution rates (0.05 h )1 , 0.16 h )1 ) with glycerol as the sole carbon source. For investigation of amino acid biosynthesis and comparison with glycerol cultivations, cells were also grown at 0.16 h )1 on glucose. Our results show that, firstly, amino acids are synthesized as inSaccharomyces cerevisiae. ...

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  • We describehere anovelmethodology for rapiddiagnosis of metabolic changes,which is basedonprobabilistic equations that relate GC-MS-derived mass distributions in proteino-genic aminoacids toin vivoenzyme activities. Thismetabolic flux ratio analysis by GC-MS provides a comprehensive perspective on central metabolism by quantifying 14 ratios of fluxes through converging pathways and reactions from [1-13 C] and [U-13 C]glucose experiments.

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  • Chapter 17 (part 1) - Amino acid metabolism: Nitrogen assimilation and amino acid biosynthesis. After completing this chapter, students will be able to: Know how different forms of nitrogen get to assimilatable form, know what types of organisms have this enzyme, know the reactions catalyzed by the enzymes below. Know structure of substrates and products, know co-enzymes and co-substrates involved,...

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  • Sterol regulatory element-binding proteins 1 and 2 (SREBP-1 and SREBP-2) are important regulators of genes involved in cholesterol and fatty acid metabolism, but have also been implicated in the regulation of the cell cycle and have been associated with the pathogenesis of type 2 diabetes, atherosclerosis and obesity, among others.

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  • Amongst a wide variety of different biochemical reactions in cellular car-bon metabolism, thiamin diphosphate-dependent enzymes catalyze the oxi-dative decarboxylation of 2-keto acids. This type of reaction typically involves redox coupled acyl transfer to CoA or phosphate and is mediated by additional cofactors, such as flavins, iron-sulfur clusters or lipoamide swinging arms, which transmit the reducing equivalents that arise during keto acid oxidation to a final electron acceptor.

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  • We show that cytochrome P450scc (CYP11A1) in either a reconstituted system or in isolated adrenal mitochondria can metabolize vita-min D3. The major products of the reaction with reconstituted enzyme were 20-hydroxycholecalciferol and 20,22-dihydroxycholecalciferol, with yields of 16 and 4%, respectively, of the original vitamin D3 substrate. Tri-hydroxycholecalciferol was a minor product, likely arising from further metabolism of dihydroxycholecalciferol.

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  • Erythrocytic stages of the malaria parasitePlasmodium fal-ciparumrely on glycolysis for their energy supply and it is unclear whether they obtain energy via mitochondrial res-piration albeit enzymes of the tricarboxylic acid (TCA) cycle appear to be expressed in these parasite stages. Isocitrate dehydrogenase (ICDH) is either an integral part of the mitochondrial TCA cycle or is involved in providing NADPH for reductive reactions in the cell.

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  • This chapter presents the following content: An organism’s metabolism transforms matter and energy, subject to the laws of thermodynamics, the free-energy change of a reaction tells us whether the reaction occurs spontaneously, ATP powers cellular work by coupling exergonic reactions to endergonic reactions,...and another contents.

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  • As discussed in Section I, no prior study examines the relation between corporate governance mechanisms and the likelihood of an earnings restatement. A few studies examine the consequences of earnings restatements. William Kinney and Linda McDaniel analyze the stock price reaction for a sample of 73 firms that restated earnings between 1976 and 1985.18 They find that, on average, stock returns are negative between issuance of erroneous quarterly statements and its corrections.

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  • IN CHAPTER 5 WE DISCUSSED plants’ requirements for mineral nutrients and light in order to grow and complete their life cycle. Because living organisms interact with one another and their environment, mineral nutrients cycle through the biosphere. These cycles involve complex interactions, and each cycle is critical in its own right. Because the amount of matter in the biosphere remains constant, energy must be supplied to keep the cycles operational. Otherwise increasing entropy dictates that the flow of matter would ultimately stop.

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  • The production of free radicals (ROS) is an unavoidable consequence of life in an aerobic environment. Free radicals produced from the metabolic activities of oxygen attack biological membranes and lipoproteins via oxidation in a process called lipid perioxidation. This attack damages cells and lipids often in a chain reaction with carbon-based molecules such as polyunsaturated fatty acids (PUFA) in a reaction with molecular oxygen. This creates oxidative stress and damage to tissues. Free radicals also damage chromosomal DNA.

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  • LIFE ON EARTH ULTIMATELY DEPENDS ON ENERGY derived from the sun. Photosynthesis is the only process of biological importance that can harvest this energy. In addition, a large fraction of the planet’s energy resources results from photosynthetic activity in either recent or ancient times (fossil fuels). This chapter introduces the basic physical principles that underlie photosynthetic energy storage and the current understanding of the structure and function of the photosynthetic apparatus (Blankenship 2002). The term photosynthesis means literally “synthesis using light.

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  • Early metabolic steps, including glycolysis and the activity of the pyruvate dehydrogenase complex, yield a two-carbon fragment called an acetyl group, which is linked to a large cofactor known as coenzyme A (or CoA). It is during the citric acid cycle that acetyl-CoA is oxidized to the waste product, carbon dioxide, along with the reduction of the cofactors NAD+ and ubiquinone

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