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9/26/2010 Chapter 5 Microbial Metabolism Prof. Johana Meléndez Copyright © 2010 Pearson Education, Inc. Lectures prepared by Christine L. Case In...
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9/26/2010

Chapter 5 Microbial Metabolism

Prof. Johana Meléndez

Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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)

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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.

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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)

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Role of ATP in Coupling Reactions

Figure 5.1 Copyright © 2010 Pearson Education, Inc.

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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 ** Copyright © 2010 Pearson Education, Inc.

Check Your Understanding Check Your Understanding  Distinguish catabolism from anabolism. 5-1  How is ATP an intermediate between catabolism and anabolism? 5-2

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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 Copyright © 2010 Pearson Education, Inc.

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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- ?

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Energy Requirements of a Chemical Reaction

•Enzymes lower the energy of activation (Ea) - ( Ea: Amount of energy required to initiate a reaction) Copyright © 2010 Pearson Education, Inc.

Figure 5.2

Components of a Holoenzyme

ANIMATION Enzymes: Overview ** ANIMATION Enzymes: Steps in a Reaction Copyright © 2010 Pearson Education, Inc.

Figure 5.3

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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 Copyright © 2010 Pearson Education, Inc.

Figure 5.4a

Enzyme Classification- not to be tested Factors Influencing Enzyme Activity    

Temperature pH Substrate concentration Inhibitors

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Factors Influencing Enzyme Activity  Temperature and pH denature proteins

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Figure 5.6

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Effect of Temperature and pH on Enzyme Activity

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Figure 5.5

Effect of Substrate Concentration on Enzyme Activity

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Figure 5.5c

Enzyme Regulation: Enzyme Inhibitors: Competitive Inhibition

ANIMATION Competitive Inhibition** Copyright © 2010 Pearson Education, Inc.

Figure 5.7a–b

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Enzyme Inhibitors: Noncompetitive Inhibition

ANIMATION Non-competitive Inhibition ** Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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? Copyright © 2010 Pearson Education, Inc.

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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. 5-10 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. 5-16 Describe the types of fermentation reactions, and list some products of fermentation Copyright © 2010 Pearson Education, Inc.

Energy generating reactions catabolism Metabolism of nutrients is important to generate ATP (Energy) ATP can be formed by: aerobic

Respiration

anaerobic

Fermentation Photosynthesis

Energy release is important for synthesis of molecules

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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

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The phosphates capture the energy and becomes part of the ATP molecule.

Fig. 8.13 The structure of adenosine triphosphate and its partner compounds, ADP and AMP. 25 Copyright © 2010 Pearson Education, Inc.

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, NO3, SO4 26

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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

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Summary of the most common pathways of glucose metabolism for the synthesis of energy.

28 Copyright © 2010 Pearson Education, Inc.

Overview of Respiration and Fermentation

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Figure 5.11

A Summary of Respiration  Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2).  Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycles operates under anaerobic conditions.

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Carbohydrate Catabolism

Pathway

Eukaryote

Prokaryote

Glycolysis

Cytoplasm

Cytoplasm

Intermediate step

Cytoplasm

Cytoplasm

Krebs cycle

Mitochondrial matrix

Cytoplasm

ETC

Mitochondrial inner membrane Plasma membrane

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Carbohydrate Catabolism  Energy produced from complete oxidation of one glucose using aerobic respiration ATP Produced

NADH Produced

FADH2 Produced

Glycolysis

2

2

0

Intermediate step

0

2

Krebs cycle

2

6

2

Total

4

10

2

Pathway

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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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An Overview of Fermentation

ANIMATION Fermentation Copyright © 2010 Pearson Education, Inc.

Figure 5.18a

End-Products of Fermentation

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Figure 5.18b

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Fermentation  Alcohol fermentation: Produces ethanol + CO2  Lactic acid fermentation: Produces lactic acid  Homolactic fermentation: Produces lactic acid only  Heterolactic fermentation: Produces lactic acid and other compounds

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Types of Fermentation

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Figure 5.19

Types of Fermentation

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Table 5.4

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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 Copyright © 2010 Pearson Education, Inc.

Biochemical Tests  Used to identify bacteria.

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Biochemical Tests  Used to identify bacteria.

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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 Copyright © 2010 Pearson Education, Inc.

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

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A Nutritional Classification of Organisms Troph- “food, nourishment” Photo- light

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Figure 5.28

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Metabolic Diversity among Organisms Nutritional Type

Energy Source

Carbon Source

Example

Photoautotroph

Light

CO2

Oxygenic: Cyanobacteria plants Anoxygenic: Green, purple bacteria

Photoheterotroph

Light

Organic compounds

Green, purple nonsulfur bacteria

Chemoautotroph

Chemical

CO2

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? Copyright © 2010 Pearson Education, Inc.

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 Copyright © 2010 Pearson Education, Inc.

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