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metabolism - Metabolism Entire network of chemical...

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1 Metabolism Entire network of chemical reactions carried out by living cells = Catabolism + Anabolism Principles of Biochemistry 3 rd ed. Ch. 11 By Horton Published by Prentice Hall Anabolism and catabolism Biopolymers, including those obtained from food, are catabolized to release energy and either monomeric building blocks or waste products. Anabolic reactions use small molecules and chemical energy thus released in the synthesis of macromoleules and in the performance of cellular work. Solar energy is and important source of metabolic energy in photosynthetic bacteria and plants.
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2 Anabolism and catabolism Catabolism Set of reactions and pathways that lead from foodstuffs to energy and building block release. – Breakdown Anabolism Set of reactions and pathways that lead to synthesis of biopolymers as well as the pathways involved in the performance of cellular work. – Buildup Though it is convenient to simplify metabolism to these two categories, some reactions and pathways seem to fit in both categories (e.g., pentose phosphate pathway) Forms of metabolic pathways (a) The biosynthesis of serine is an example of a linear metabolic pathway. The product of each step is the substrate for the next step. (b) The sequence of reactions in a cyclic pathway forms a closed loop. In the citric acid cycle, an acetyl group is metabolized via reactions that regenerate the intermediates of the cycle. (c) In fatty acid biosynthesis, a spiral pathway, the same set of enzymes catalyze a progressive lengthening of the acyl chain.
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