Chapter10Fall2005 - Chapter 10 Introduction to Metabolism metabolism sum total of all chemical reactions in living cells catabolic reactions

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Chapter 10 - Introduction to Metabolism metabolism - sum total of all chemical reactions in living cells catabolic reactions - degrade macromolecules and other molecules to release energy anabolic reactions - used to synthesize macromolecules for cell growth, repair, and reproduction Can divide metabolism into 4 groups: carbohydrates, lipids, amino acids, nucleotides. within each group are a set of pathways arbitrarily set start and end points for ease of learning and reference pathways can take different forms: 1) linear - product of one reaction is substrate for another e.g. glycolysis 2) cyclic - regeneration of intermediates e.g. Krebs cycle 3) spiral - same set of enzymes is used repeatedly e.g. fatty acid synthesis, β -oxidation each pathway may have branch points for metabolites to enter or leave Why have metabolic reactions with so many steps? 1) energy input and output can be controlled - energy transfer occurs in discrete steps as it it transferred to acceptors a little at a time 2) enzymes can catalyze only a single step of a pathway 3) provides opportunities to establish control points, which are essential for cell function Methods of Metabolic Pathway Regulation 1) feedback inhibition product of pathway controls its own rate of synthesis occurs in the first committed step E 1 E 2 E 3 A -----> B -----> C -----> D advantage is obvious --> prevention of intermediate accumulation 2) feed forward activation (positive feedback) metabolite produced early in pathway activates an enzyme later in pathway also prevents accumulation of intermediates
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7 E 1 E 2 E 3 E 4 A -----> B -----> C -----> D -----> E 3) allosteric activators and inhibitors 4) covalent modification addition of phosphoryl groups via protein kinases
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This note was uploaded on 08/02/2009 for the course BIOCHEMIST 100 taught by Professor Crew during the Spring '05 term at North Alabama.

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Chapter10Fall2005 - Chapter 10 Introduction to Metabolism metabolism sum total of all chemical reactions in living cells catabolic reactions

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