Chapter 5 9/26/2010. Interesting facts

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1 Chapter 5 Microbial Metabolism Prof. Johana Meléndez Lectures prepared by Christine L. Case Interesting facts Wine to - vinegar connection wine is a result of microbial fermentation Undesirable microbes contaminated wine producing acids Likely to be Acetobacter or Gluconobacter Gram negative bacteria use to oxidize ethanol into acetic acid 2 Relationship of these to bacterial metabolism? E. coli O157:H7 (causes the most severe food borne disease) looks like the normal E.coli. How can we then differentiate it from the good one? Wine, cheese, alcohol, acids Antibiotics Dead zones (Chesapeake bay article) 3 1

2 Catabolic and Anabolic Reactions Learning Objectives 5-1 Define metabolism, and describe the fundamental differences between anabolism and catabolism. 5-2 Identify the role of ATP as an intermediate between catabolism and anabolism. Catabolic and Anabolic Reactions Metabolism: The sum of the chemical reactions in an organism Catabolism: Provides energy and building blocks for anabolism. (releases energy) Anabolism: Uses energy and building blocks to build large molecules (requires energy) Role of ATP in Coupling Reactions Figure 5.1 2

3 Catabolic and Anabolic Reactions A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell Metabolic pathways are determined by enzymes Enzymes are encoded by genes ANIMATION Metabolism: Overview ** Check Your Understanding Check Your Understanding Distinguish catabolism from anabolism. 5-1 How is ATP an intermediate between catabolism and anabolism? 5-2 Enzyme Learning Objectives 5-3 Identify the components of an enzyme. 5-4 Describe the mechanism of enzymatic action. *Why is enzyme specificity so important? 5-5 List the factors that influence enzymatic activity. * What happens to enzymes exposed to non optimal factors like temperature, ph? 5-6 Distinguish competitive and noncompetitive inhibition. *Compare and contrast between the two types of enzyme regulation 3

4 Enzymes Catalyze the chemical reactions of life can catalyze 10,000 Rx / second Enzymes: an example of catalysts, chemicals that increase the rate of a chemical reaction without becoming part of the products or being consumed in the reaction Names usually end with ase Catalase (breaks down hydrogen peroxide) Lactase-? 10 Energy Requirements of a Chemical Reaction Enzymes lower the energy of activation (Ea) - ( Ea: Amount of energy required to initiate a reaction) Figure 5.2 Components of a Holoenzyme ANIMATION Enzymes: Overview ** ANIMATION Enzymes: Steps in a Reaction Figure 5.3 4

5 The Mechanism of Enzymatic Action Have a unique site to fit the substrate: active site or catalytic site. ( lock and key but flexible) Substrate: reactant molecules E + S ES- E + P Figure 5.4a Enzyme Classification- not to be tested Factors Influencing Enzyme Activity Temperature ph Substrate concentration Inhibitors Factors Influencing Enzyme Activity Temperature and ph denature proteins Figure 5.6 5

6 Effect of Temperature and ph on Enzyme Activity Figure 5.5 Effect of Substrate Concentration on Enzyme Activity Figure 5.5c Enzyme Regulation: Enzyme Inhibitors: Competitive Inhibition ANIMATION Competitive Inhibition** Figure 5.7a b 6

7 Enzyme Inhibitors: Noncompetitive Inhibition ANIMATION Non-competitive Inhibition ** Figure 5.7a, c Roles of enzymes on disease Enzymes can be called toxins or virulence factors Help them avoid host defenses or promote multiplication in tissues S. pyogens (cause throat and skin infections) produces streptokinase that digest blood clots, help entrance to wounds. C. perfringens - has lipase that damages cell membranes, accounts for the tissue death Penicillinase -?? 20 Check Your Understanding Check Your Understanding What is a coenzyme? 5-3 Why is enzyme specificity important? 5-4 What happens to an enzyme below its optimal temperature? Above its optimal temperature? 5-5 What is competitive and non competitive inhibition? How are they similar/ different? Provide an example of the role of enzyme on disease? 7

8 Energy Production Learning Objectives 5-9 List and provide examples of three types of reactions that generate ATP. * Outline the three ways that ATP is generated Explain the overall function of metabolic pathways. * What is the purpose of metabolic pathways? 5-15 Compare and contrast aerobic, anaerobic respiration and fermentation in terms of oxygen use and amount of ATP produced Describe the types of fermentation reactions, and list some products of fermentation Energy generating reactions catabolism Metabolism of nutrients is important to generate ATP (Energy) ATP can be formed by: Respiration Fermentation aerobic anaerobic Photosynthesis Energy release is important for synthesis of molecules 23 Adenosine Triphosphate (ATP) Metabolic Money Temporary energy repository Breaking of phosphates bonds will release free energy Three part molecule Nitrogen base 5-carbon sugar (ribose) Chain of phosphates 24 8

9 The phosphates capture the energy and becomes part of the ATP molecule. Fig The structure of adenosine triphosphate and its partner compounds, ADP and AMP. 25 Catabolism: Energy generating reactions Respiration: transfer of e-, energy is release and stored in high energy bonds. aerobic anaerobic Oxygen is the final e- acceptor Inorganic molecules as the final e- acceptor, NO 3, SO 4 26 Respiration: Carbohydrate catabolism Aerobic respiration: (3 major steps): 1. Glycolysis (2 ATP net) 2. Krebs cycle: Tricarboxylic acid (TCA) (2 ATP net) 3. Electron transport chain (34 ATP net) 38 ATP total output per glucose 27 9

10 Summary of the most common pathways of glucose metabolism for the synthesis of energy. 28 Overview of Respiration and Fermentation Figure 5.11 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. Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions. 10

11 Carbohydrate Catabolism Pathway Eukaryote Prokaryote Glycolysis Cytoplasm Cytoplasm Intermediate step Cytoplasm Cytoplasm Krebs cycle Mitochondrial matrix Cytoplasm ETC Mitochondrial inner membrane Plasma membrane Carbohydrate Catabolism Energy produced from complete oxidation of one glucose using aerobic respiration Pathway ATP Produced NADH Produced FADH 2 Produced Glycolysis Intermediate step 0 2 Krebs cycle Total 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) 11

12 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 An Overview of Fermentation ANIMATION Fermentation Figure 5.18a End-Products of Fermentation Figure 5.18b 12

13 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 Types of Fermentation Figure 5.19 Types of Fermentation Table

14 Energy Production Check your understanding List the three types of reactions that generate ATP. What is the purpose of metabolic pathways? Compare and contrast aerobic, anaerobic respiration and fermentation in terms of oxygen use and amount of ATP produced. How many glucose molecules we need in order to generate 38 ATP through fermentation? 1glucose generates 2 ATP by fermentation Describe the types of fermentation reactions, and list some products of fermentation Biochemical Tests Used to identify bacteria. Biochemical Tests Used to identify bacteria. 14

15 Relationship of these to bacterial metabolism? E. coli O157:H7 (causes the most severe food borne disease) looks like the normal E.coli. How can we differentiate E. coli (good one) from E. coli O157 (bad one)? 43 Metabolic Diversity among Organisms Learning Objective 5-23 Categorize the various nutritional patterns among organisms according to carbon source and mechanisms of carbohydrate catabolism and ATP generation. * This material will be for extra credit on next test A Nutritional Classification of Organisms Troph- food, nourishment Photo- light Figure

16 Metabolic Diversity among Organisms Nutritional Type Energy Source Carbon Source Example Photoautotroph Light CO 2 Oxygenic: Cyanobacteria plants Anoxygenic: Green, purple bacteria Photoheterotroph Light Organic compounds Green, purple nonsulfur bacteria Chemoautotroph Chemical CO 2 Iron-oxidizing bacteria Chemoheterotroph Chemical Organic compounds Fermentative bacteria Animals, protozoa, fungi, bacteria. Almost all the medically important microbes belong to which of the four aforementioned groups? Chemoheterotrophs Chemoheterotrophs can obtain energy and Carbon from the same organic compound. Ex. Pseudomonas can use over 90 organic compounds for source of Energy and Carbon. Can grow in soap dispensers. And respiratory equipment!! 47 16