Microbial Metabolism Ch 5

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Microbial MetabolismCh 5

• Metabolism is the sum of the chemical reactions
  in an organism.
• Catabolism is the energy-releasing processes.
• Anabolism is the energy-using processes.
  (typically building something)

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Microbial Metabolism

• Catabolism provides the building blocks and
  energy for anabolism.

Figure 5.1
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Amphibolic pathways

• Are metabolic pathways that have both catabolic
  and anabolic functions.
• This is basically all of life

Figure 5.32.1
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Amphibolic pathways
Figure 5.32.2
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• A metabolic pathway is a sequence of
  enzymatically catalyzed chemical reactions in a
  cell.
• A primary metabolic pathway are the reactions
  that do the basic work of the cell. Get food and
  grow
• Metabolic pathways are determined by enzymes.
• Enzymes are encoded by genes.

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Biochemical tests

• Used to identify bacteria.
• Enzymes are genes
• Sum of genes is your organism

Figure 10.8
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Enzymes
Figure 5.2
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Enzymes

• Biological catalysts
• Specific for a chemical reaction not used up in
  that reaction
• Apoenzyme protein
• Cofactor Nonprotein component
• Coenzyme Organic cofactor
• Holoenzyme Apoenzyme cofactor

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Enzymes
Figure 5.3
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Important Coenzymes

• NAD
• NADP
• FAD
• Coenzyme A
• Biotin
• Folic acid
• Many of the vitamins

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Enzymes

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

Figure 5.4
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Factors Influencing Enzyme Activity

• Enzymes can be denatured by temperature and pH

Figure 5.6
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Factors Influencing Enzyme Activity

• Temperature

Figure 5.5a
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Factors Influencing Enzyme Activity

• pH

Figure 5.5b
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Factors Influencing Enzyme Activity

• Substrate concentration

Figure 5.5c
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Factors Influencing Enzyme Activity

• Competitive inhibition

Figure 5.7a, b
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Factors Influencing Enzyme Activity
Sulfa inhibits the enzyme that uses PABA for
synthesis of folic acid
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Factors Influencing Enzyme Activity

• Noncompetitive inhibition

Figure 5.7a, c
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• Feedback inhibition

Figure 5.8
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The Generation of ATP

• ATP is generated by the phosphorylation of ADP.

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The Generation of ATP

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

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The Generation of ATP

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

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Metabolic Pathways
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Carbohydrate Catabolism

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

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Glycolysis

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

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Preparatory Stage
Preparatory Stage
Glucose
1

• 2 ATPs are used
• Glucose is split to form 2 Glyceraldehyde-3-phosph
  ate

Glucose 6-phosphate
2
Fructose 6-phosphate
3
Fructose 1,6-diphosphate
4
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Glyceraldehyde 3-phosphate (GP)
Dihydroxyacetone phosphate (DHAP)
Figure 5.12.1
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Energy-Conserving Stage
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1,3-diphosphoglyceric acid
7

• 2 Glucose-3-phosphate oxidized to 2 Pyruvic acid
• 4 ATP produced
• 2 NADH produced

3-phosphoglyceric acid
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2-phosphoglyceric acid
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Phosphoenolpyruvic acid (PEP)
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Pyruvic acid
Figure 5.12.2
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Glycolysis

• Glucose 2 ATP 2 ADP 2 PO4 2 NAD ? 2
  pyruvic acid 4 ATP 2 NADH 2H

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Alternatives to Glycolysis

• Pentose phosphate pathway
• Uses pentoses and NADPH
• Operates with glycolysis
• Use and production of 5 carbon sugars (na)
• Bacillus subtilis, E. coli, Enterococcus faecalis
• Entner-Doudoroff pathway
• Produces NADPH and ATP
• Does not involve glycolysis
• Pseudomonas, Rhizobium, Agrobacterium

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Cellular Respiration

• Oxidation of molecules liberates electrons for an
  electron transport chain
• ATP generated by oxidative phosphorylation

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Intermediate Step

• Pyruvic acid (from glycolysis) is oxidized and
  decarboyxlated

Figure 5.13.1
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Krebs Cycle

• Oxidation of acetyl CoA produces NADH and FADH2

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Krebs Cycle
Figure 5.13.2
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The Electron Transport Chain

• A series of carrier molecules that are, in turn,
  oxidized and reduced as electrons are passed down
  the chain.
• Energy released can be used to produce ATP by
  chemiosmosis.

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Chemiosmosis
Figure 5.15
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Electron transport and Chemiosmosis
Figure 5.16.2
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Figure 5.14
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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 operations
  under anaerobic conditions.

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Anaerobic respiration
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• Energy produced from complete oxidation of 1
  glucose using aerobic respiration

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• ATP produced from complete oxidation of 1 glucose
  using aerobic respiration
• 36 ATPs are produced in eukaryotes.

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Fermentation

• 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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Fermentation
Figure 5.18b
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Fermentation

• Alcohol fermentation. Produces ethyl alcohol
  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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Fermentation
Figure 5.19
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Fermentation
Production of acid and gas
Figure 5.23
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Lipid Catabolism
Figure 5.20
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Protein Catabolism
Extracellular proteases
Protein
Amino acids
Deamination, decarboxylation, dehydrogenation
Krebs cycle
Organic acid
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Biochemical tests

• Used to identify bacteria.

Figure 10.8
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• Halobacterium uses bacteriorhodopsin, not
  chlorophyll, to generate electrons for a
  chemiosmotic proton pump.

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Chemotrophs

• Use energy from chemicals.
• Chemoheterotroph
• Energy is used in anabolism.

Glucose
NAD
ETC
Pyruvic acid
NADH
ADP P
ATP
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Chemotrophs

• Use energy from chemicals.
• Chemoautotroph, Thiobacillus ferroxidans
• Energy used in the Calvin-Benson cycle to fix CO2.

2Fe2
NAD
ETC
2Fe3
NADH
ADP P
ATP
2 H
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Metabolic Diversity Among Organisms
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Metabolic Pathways of Energy Use

• Polysaccharide Biosynthesis

Figure 5.28
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Metabolic Pathways of Energy Use

• Lipid Biosynthesis

Figure 5.29
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Metabolic Pathways of Energy Use

• Amino Acid and Protein Biosynthesis

Figure 5.30a
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Metabolic Pathways of Energy Use

• Amino Acid and Protein Biosynthesis

Figure 5.30b
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Metabolic Pathways of Energy Use

• Purine and Pyrimidine Biosynthesis

Figure 5.31
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Amphibolic pathways

• Are metabolic pathways that have both catabolic
  and anabolic functions.

Figure 5.32.1
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Amphibolic pathways
Figure 5.32.2