lecture_19legge - Introduction to metabolism Metabolism is...

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10/26/2009 1 Metabolism 10/27/09 Introduction to metabolism Metabolism is the overall process through which living systems acquire and utilize free energy to carry out their functions They couple exergonic reactions of nutrient breakdown to the endergonic processes breakdown to the endergonic processes required to maintain the living state How do living things acquire the energy needed for these functions? Catabolism (degradation): nutrients and cell constituents broken down to salvage components and/or generate energy Anabolism (biosynthesis): biomolecules are synthesized from simpler components Autotrophs – self-feeders (synthesize their own cellular constituents from H 2 O, CO 2 , NH 3 , and H 2 S) Photoautotrophs - acquire free energy from sunlight Chemolithotrophs – obtain free energy from oxidation of inorganic compounds such as NH 3 , H 2 S, or Fe 2+ . Heterotrophs – oxidize organic compounds to make ATP ATP is the energy carrier for most biological reactions Organisms can be classified by the identity of the oxidizing agent. Obligate aerobes: must use O 2 Anaerobes: use sulfate or nitrate Facultative anaerobes: can grow in presence or absence of O 2 (e.g. E. coli ) Obligate anaerobes: poisoned by O 2 Metabolic pathways are series of connected enzymatic reactions that produce specific products. Their reactants, inter- mediates, and products are called metabolites . There are over 2000 known metabolic reactions – see figure to the left. Organizing metabolic reactions See these useful sites below: http://www.genome.jp/kegg/m etabolism.html http://www.genome.jp/kegg/pa thway/map/map01100.html If you click on the “Carbohydrate Metabolism” button, you will get the clickable image on the next slide
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