Microbiology Introduction Chapter 5 PDF

Microbiology an Introduction Twelfth Edition Chapter 5 Microbial Metabolism Copyright © 2016 Pearson Education, Inc. All Rights Reserved Dental Plaque Consists of Bacteria Copyright © 2016 Pearson Ed...

Microbiology an Introduction Twelfth Edition Chapter 5 Microbial Metabolism Copyright © 2016 Pearson Education, Inc. All Rights Reserved Dental Plaque Consists of Bacteria Copyright © 2016 Pearson Education, Inc. All Rights Reserved Big Picture: Metabolism (1 of 2) Metabolism is the buildup and breakdown of nutrients within a cell These chemical reactions provide energy and create substances that sustain life Copyright © 2016 Pearson Education, Inc. All Rights Reserved Big Picture pg. 108 Copyright © 2016 Pearson Education, Inc. All Rights Reserved Big Picture: Metabolism (2 of 2) Although microbial metabolism can cause disease and food spoilage, many pathways are beneficial rather than pathogenic Copyright © 2016 Pearson Education, Inc. All Rights Reserved Big Picture pg. 109 Copyright © 2016 Pearson Education, Inc. All Rights Reserved Catabolic and Anabolic Reactions (2 of 3) Catabolism: breaks down complex molecules; provides energy and building blocks for anabolism; exergonic Anabolism: uses energy and building blocks to build complex molecules; endergonic Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.1 The role of ATP in Coupling Anabolic and Catabolic Reactions Copyright © 2016 Pearson Education, Inc. All Rights Reserved Catabolic and Anabolic Reactions (3 of 3) Metabolic pathways are sequences of enzymatically catalyzed chemical reactions in a cell Metabolic pathways are determined by enzymes Enzymes are encoded by genes Copyright © 2016 Pearson Education, Inc. All Rights Reserved Collision Theory The collision theory states that chemical reactions occur when atoms, ions, and molecules collide Activation energy is the collision energy required for a chemical reaction to occur Reaction rate is the frequency of collisions containing enough energy to bring about a reaction – Reaction rate can be increased by enzymes or by increasing temperature, pressure, or concentration Copyright © 2016 Pearson Education, Inc. All Rights Reserved Enzymes and Chemical Reactions (1 of 2) Catalysts speed up chemical reactions without being altered Enzymes are biological catalysts Enzymes act on a specific substrate and lower the activation energy Copyright © 2016 Pearson Education, Inc. All Rights Reserved Enzymes and Chemical Reactions (2 of 2) Substrate contacts the enzyme’s active site to form an enzyme-substrate complex Substrate is transformed and rearranged into products, which are released from the enzyme Enzyme is unchanged and can react with other substrates Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.3a The Mechanism of Enzymatic Action Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.3b The Mechanism of Enzymatic Action Copyright © 2016 Pearson Education, Inc. All Rights Reserved Enzyme Specificity and Efficiency Enzymes have specificity for particular substrates Turnover number is the number of substrate molecules an enzyme converts to a product per second – Generally 1 to 10,000 Copyright © 2016 Pearson Education, Inc. All Rights Reserved Naming Enzymes Names of enzymes usually end in ase; grouped based on the reaction they catalyze Oxidoreductase: oxidation-reduction reactions Transferase: transfer functional groups Hydrolase: hydrolysis Lyase: removal of atoms without hydrolysis Isomerase: rearrangement of atoms Ligase: joining of molecules; uses ATP Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.4 Components of a Holoenzyme Copyright © 2016 Pearson Education, Inc. All Rights Reserved Factors Influencing Enzyme Activity (1 of 2) Temperature pH Substrate concentration Inhibitors Copyright © 2016 Pearson Education, Inc. All Rights Reserved Factors Influencing Enzyme Activity (2 of 2) High temperature and extreme pH denature proteins If the concentration of substrate is high (saturation), the enzyme catalyzes at its maximum rate Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.6 Denaturation of a Protein Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.5a Factors that Influence Enzymatic Activity, Plotted for a Hypothetical Enzyme (a) Temperature. The enzymatic activity (rate of reaction catalyzed by the enzyme) increases with increasing temperature until the enzyme, a protein, is denatured by heat and inactivated. At this point, the reaction rate falls steeply. Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.5b Factors that Influence Enzymatic Activity, Plotted for a Hypothetical Enzyme (b) pH. The enzyme illustrated is most active at about pH 5.0. Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.5c Factors that Influence Enzymatic Activity, Plotted for a Hypothetical Enzyme (c) Substrate concentration. With increasing concentration of substrate molecules, the rate of reaction increases until the active sites on all the enzyme molecules are filled, at which point the maximum rate of reaction is reached. Copyright © 2016 Pearson Education, Inc. All Rights Reserved Inhibitors (1 of 2) Competitive inhibitors fill the active site of an enzyme and compete with the substrate Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.7a-b Enzyme Inhibitors Copyright © 2016 Pearson Education, Inc. All Rights Reserved Unnumbered Figure pg. 115 Copyright © 2016 Pearson Education, Inc. All Rights Reserved Inhibitors (2 of 2) Noncompetitive inhibitors interact with another part of the enzyme (allosteric site) rather than the active site in a process called allosteric inhibition Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.7a-c Enzyme Inhibitors Copyright © 2016 Pearson Education, Inc. All Rights Reserved Feedback Inhibition End-product of a reaction allosterically inhibits enzymes from earlier in the pathway Copyright © 2016 Pearson Education, Inc. All Rights Reserved Figure 5.8 Feedback Inhibition Copyright © 2016 Pearson Education, Inc. All Rights Reserved Ribozymes RNA that function as catalysts by cutting and splicing RNA Copyright © 2016 Pearson Education, Inc. All Rights Reserved