Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 Chapters 8-10 Metabolisms

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2 An Overview of Metabolism metabolism –total of all chemical reactions occurring in cell catabolism –breakdown of larger, more complex molecules into smaller, simpler ones –energy is released and some is trapped and made available for work anabolism –synthesis of complex molecules from simpler ones with the input of energy

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 3 Sources of energy Figure 9.1 electrons released during oxidation of chemical energy sources must be accepted by an electron acceptor microorganisms vary in terms of the acceptors they use

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 Electron acceptors for chemotrophic processes Figure 9.2 exogenous electron acceptors

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 5 Chemoorganotrophic metabolism fermentation –energy source oxidized and degraded using endogenous electron acceptor –often occurs under anaerobic conditions –limited energy made available

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 6 Chemoorganotrophic metabolism aerobic respiration –energy source degraded using oxygen as exogenous electron acceptor –yields large amount of energy, primarily by electron transport activity

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 7 Chemoorganotrophic metabolism anaerobic respiration –energy source oxidized and degraded using molecules other than oxygen as exogenous electron acceptors –can yield large amount of energy (depending on reduction potential of energy source and electron acceptor), primarily by electron transport activity

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 8 Overview of aerobic catabolism three-stage process –large molecules (polymers)  small molecules (monomers) –initial oxidation and degradation to pyruvate –oxidation and degradation of pyruvate by the tricarboxylic acid cycle (TCA cycle)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 9 Figure 9.3 many different energy sources are funneled into common degradative pathways ATP made primarily by oxidative phosphory- lation

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 10 Two functions of organic energy sources oxidized to release energy supply carbon and building blocks for anabolism –amphibolic pathways function both as catabolic and anabolic pathways Figure 9.4

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 11 The Breakdown of Glucose to Pyruvate Three common routes –glycolysis –pentose phosphate pathway –Entner-Doudoroff pathway

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 12 The Glycolytic Pathway also called Embden-Meyerhof pathway occurs in cytoplasmic matrix of both procaryotes and eucaryotes

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 13 Figure 9.5 addition of phosphates “primes the pump” oxidation step – generates NADH high-energy molecules – used to synthesize ATP by substrate-level phosphorylation

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 14 Summary of glycolysis glucose + 2ADP + 2P i + 2NAD +  2 pyruvate + 2ATP + 2NADH + 2H +

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 15 The Entner-Doudoroff Pathway yield per glucose molecule: –1 ATP –1 NADPH –1 NADH Figure 9.8 reactions of glycolytic pathway reactions of pentose phosphate pathway

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 18 Fermentations oxidation of NADH produced by glycolysis pyruvate or derivative used as endogenous electron acceptor ATP formed by substrate-level phosphorylation Figure 9.9

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 19 Figure 9.10 homolactic fermenters heterolactic fermenters food spoilage yogurt, sauerkraut, pickles, etc. alcoholic fermentation alcoholic beverages, bread, etc.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 20 methyl red test – detects pH change in media caused by mixed acid fermentation

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 21 Butanediol fermentation Voges-Proskauer test – detects intermediate acetoin Methyl red test and Voges- Proskauer test important for distinguishing pathogenic members of Enterobacteriaceae

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 22 Fermentations of amino acids Stickland reaction –oxidation of one amino acid with use of second amino acid as electron acceptor Figure 9.11

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 23 Procaryotic ETCs located in plasma membrane some resemble mitochondrial ETC, but many are different –different electron carriers –may be branched –may be shorter –may have lower P/O ratio

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 24 ETC of E. coli Figure 9.15 branched pathway upper branch – stationary phase and low aeration lower branch – log phase and high aeration

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 25 ETC of Paracoccus denitrificans - aerobic Figure 9.16a

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26 ETC of P. denitrificans - anaerobic Figure 9.16b example of anaerobic respiration

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 27 Reserve Polymers used as energy sources in absence of external nutrients –e.g., glycogen and starch cleaved by phosphorylases (glucose) n + P i  (glucose) n-1 + glucose-1-P glucose-1-P enters glycolytic pathway –e.g., PHB PHB    acetyl-CoA acetyl-CoA enters TCA cycle

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 28 Peptidoglycan Synthesis complex multi-stage process –first forms peptidoglycan repeat unit in cytoplasm involves use of uridine diphosphate and bactoprenol as carriers –repeat unit then transported across membrane by bactoprenol –repeat unit attached to growing peptidoglycan chain –cross-links formed by transpeptidation

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 30 Figure 10.28

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 32 Figure bactoprenol attached to N-acetylmuramic acid (NAM)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 33 Figure 10.29

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