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UNIT 2: BACTERIAL METABOLISM AND FERMENTATION

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Fermentation and Pasteurization Pasteur showed that microbes are responsible for fermentation Fermentation is the conversion of sugar to alcohol or acid Fermentation is used to make cheese, yogurt, beer and wine Microbial growth is also responsible for spoilage of food Bacteria that use alcohol and produce acetic acid spoil wine by turning it to vinegar (acetic acid) and bacteria that utilize lactose to produce lactic acid transform milk into yogurt

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Figure 1.4 Fermentation and Pasteurization Pasteur demonstrated that these spoilage bacteria could be killed by heat that was not hot enough to evaporate the alcohol in wine Pasteurization is the application of a high heat for a short time

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Figure 5.28 A Nutritional Classification of Organisms

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Figure 5.28 A Nutritional Classification of Organisms

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Figure 5.28 A Nutritional Classification of Organisms

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Nutritional TypeEnergy SourceCarbon SourceExample PhotoautotrophLightCO 2 Oxygenic: Cyanobacteria plants Anoxygenic: Green, purple bacteria PhotoheterotrophLightOrganic compounds Green, purple nonsulfur bacteria ChemoautotrophChemicalCO 2 Iron-oxidizing bacteria ChemoheterotrophChemicalOrganic compounds Fermentative bacteria Animals, protozoa, fungi, bacteria. Metabolic Diversity among Organisms

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Carbohydrate Catabolism The breakdown of carbohydrates to release energy Glycolysis Krebs cycle Electron transport chain

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A Summary of Respiration Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O 2 ). Anaerobic respiration: The final electron acceptor in the electron transport chain is not O 2 (rather an inorgainc molecules containing sulfate, nitrate, nitrite, carbonate, etc..). Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions.

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Glycolysis The oxidation of glucose to pyruvic acid produces ATP and NADH

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Figure 5.12, steps 15 Preparatory Stage of Glycolysis 2 ATP are invested Glucose is split to form 2 glucose-3 -phosphate

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Cellular Respiration Oxidation of molecules liberates electrons for an electron transport chain ATP is generated by oxidative phosphorylation

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Figure 5.12, steps 610 Energy-Generating Stage of Glycolysis 2 glucose-3- phosphate oxidized to 2 pyruvic acid 4 ATP produced 2 NADH produced

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Overall Result of Glycolysis Glucose + 2 ATP + 2 ADP + 2 PO 4 + 2 NAD + 2 pyruvic acid + 4 ATP + 2 NADH + 2H +

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Figure 5.13 Intermediate Step Pyruvic acid (from glycolysis) is oxidized and decarboyxlated

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Acetyl CoA

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The Krebs Cycle

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PathwayEukaryoteProkaryote GlycolysisCytoplasm Intermediate stepCytoplasm Krebs cycleMitochondrial matrixCytoplasm ETCMitochondrial inner membranePlasma membrane Carbohydrate Catabolism

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The Electron Transport Chain A series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chain Energy released can be used to produce ATP by chemiosmosis

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Figure 5.16 Chemiosmotic Generation of ATP

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Figure 5.15 An Overview of Chemiosmosis

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Fermentation Any spoilage of food by microorganisms (general use) Any process that produces alcoholic beverages or acidic dairy products (general use) Any large-scale microbial process occurring with or without air (common definition used in industry)

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Fermentation Scientific definition: Releases energy from oxidation of organic molecules Does not require oxygen Does not use the Krebs cycle or ETC Uses an organic molecule as the final electron acceptor

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Figure 5.11

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Figure 5.18a An Overview of Fermentation

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Fermentation Alcohol fermentation: Produces ethanol + CO 2 Lactic acid fermentation: Produces lactic acid Homolactic fermentation: Produces lactic acid only Heterolactic fermentation: Produces lactic acid and other compounds

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Figure 5.19 Types of Fermentation

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Figure 5.18b End-Products of Fermentation

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Figure 5.23 A Fermentation Test

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Table 5.4 Types of Fermentation

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Table 5.4 Types of Fermentation

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Figure 5.27 Requirements of ATP Production