tortora • funke • case...
TRANSCRIPT
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
MicrobiologyB.E Pruitt & Jane J. Stein
AN INTRODUCTIONEIGHTH EDITION
TORTORA • FUNKE • CASE
Chapter 5, part AMicrobial Metabolism
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Microbial Metabolism
• Metabolism is the sum of the chemical reactions in an organism.
• Catabolism is the energy-releasing processes.• Anabolism is the energy-using processes.
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• Catabolism provides the building blocks and energy for anabolism.
Microbial Metabolism
Figure 5.1
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• 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.
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• The collision theory states that chemical reactions can occur when atoms, ions, and molecules collide.
• Activation energy is needed to disrupt electronic configurations.
• Reaction rate is the frequency of collisions with enough energy to bring about a reaction.
• Reaction rate can be increased by enzymes or by increasing temperature or pressure.
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Enzymes
Figure 5.2
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• Biological catalysts• Specific for a chemical reaction; not used up in that
reaction• Apoenzyme: protein• Cofactor: Nonprotein component
• Coenzyme: Organic cofactor• Holoenzyme: Apoenzyme + cofactor
Enzymes
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Enzymes
Figure 5.3
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• NAD+
• NADP+
• FAD• Coenzyme A
Important Coenzymes
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• The turnover number is generally 1-10,000 molecules per second.
Enzymes
Figure 5.4
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• 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
Enzyme Classification
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• Enzymes can be denatured by temperature and pH
Factors Influencing Enzyme Activity
Figure 5.6
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• Temperature
Factors Influencing Enzyme Activity
Figure 5.5a
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• pH
Factors Influencing Enzyme Activity
Figure 5.5b
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• Substrate concentration
Factors Influencing Enzyme Activity
Figure 5.5c
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• Competitive inhibition
Factors Influencing Enzyme Activity
Figure 5.7a, b
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Factors Influencing Enzyme Activity
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• Noncompetitive inhibition
Factors Influencing Enzyme Activity
Figure 5.7a, c
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• Feedback inhibition
Factors Influencing Enzyme Activity
Figure 5.8
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• RNA that cuts and splices RNA
Ribozymes
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• Oxidation is the removal of electrons.• Reduction is the gain of electrons.• Redox reaction is an oxidation reaction paired with a
reduction reaction.
Oxidation-Reduction
Figure 5.9
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• In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.
Oxidation-Reduction
Figure 5.10
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• ATP is generated by the phosphorylation of ADP.
The Generation of ATP
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• Substrate-level phosphorylation is the transfer of a high-energy PO4
- to ADP.
The Generation of ATP
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• Energy released from the transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP by chemiosmosis.
The Generation of ATP
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• Light causes chlorophyll to give up electrons. Energy released from the transfer of electrons (oxidation) of chlorophyll through a system of carrier molecules is used to generate ATP.
The Generation of ATP
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Metabolic Pathways
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• The breakdown of carbohydrates to release energy• Glycolysis• Krebs cycle• Electron transport chain
Carbohydrate Catabolism
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• The oxidation of glucose to pyruvic acid, produces ATP and NADH.
Glycolysis
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• 2 ATPs are used• Glucose is split to
form 2 Glucose-3-phosphate
Preparatory Stage
Figure 5.12.1
PreparatoryStage
Glucose
Glucose6-phosphate
Fructose6-phosphate
Fructose1,6-diphosphate
Dihydroxyacetonephosphate (DHAP)
Glyceraldehyde3-phosphate(GP)
1
2
3
4
5
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• 2 Glucose-3-phosphate oxidized to 2 Pyruvic acid
• 4 ATP produced• 2 NADH produced
Energy-Conserving Stage
Figure 5.12.2
1,3-diphosphoglyceric acid
3-phosphoglyceric acid
2-phosphoglyceric acid
Phosphoenolpyruvic acid(PEP)
6
7
8
9
10
Pyruvic acid
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• Glucose + 2 ATP + 2 ADP + 2 PO4– + 2 NAD+ →
2 pyruvic acid + 4 ATP + 2 NADH + 2H+
Glycolysis
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• Pentose phosphate pathway:• Uses pentoses and NADPH• Operates with glycolysis
• Entner-Doudoroff pathway: • Produces NADPH and ATP• Does not involve glycolysis• Pseudomonas, Rhizobium, Agrobacterium
Alternatives to Glycolysis