tortora • funke • case...

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


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.


• Catabolism provides the building blocks and energy for anabolism.

Microbial Metabolism

Figure 5.1


• 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.


• 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.


Enzymes

Figure 5.2


• 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


Enzymes

Figure 5.3


• NAD+

• NADP+

• FAD• Coenzyme A

Important Coenzymes


• The turnover number is generally 1-10,000 molecules per second.

Enzymes

Figure 5.4


• 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


• Enzymes can be denatured by temperature and pH

Factors Influencing Enzyme Activity

Figure 5.6


• Temperature


Figure 5.5a


• pH


Figure 5.5b


• Substrate concentration


Figure 5.5c


• Competitive inhibition


Figure 5.7a, b


• Noncompetitive inhibition


Figure 5.7a, c


• Feedback inhibition


Figure 5.8


• RNA that cuts and splices RNA

Ribozymes


• 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


• In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.

Oxidation-Reduction

Figure 5.10


• ATP is generated by the phosphorylation of ADP.

The Generation of ATP


• Substrate-level phosphorylation is the transfer of a high-energy PO4

- to ADP.



• Energy released from the transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP by chemiosmosis.



• 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.



Metabolic Pathways


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

Carbohydrate Catabolism


• The oxidation of glucose to pyruvic acid, produces ATP and NADH.

Glycolysis


• 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


• 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


• Glucose + 2 ATP + 2 ADP + 2 PO4– + 2 NAD+ →

2 pyruvic acid + 4 ATP + 2 NADH + 2H+

Glycolysis


• 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

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