Chapter 5
Metabolism of Microorganisms
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Metabolism in the cell
Figure 5.1
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Biosynthesis in a cell
• Composition of cell
–
–
–
–
–
–
–
–
–
protein
RNA
DNA
Lipid
Lipopolysacharide
Peptidoglycan
Glycogen
Small molecules
Ions
Figure 5.2
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Transport into the cell
• Outer membrane
– pass through porin
• small size
• concentration gradient
• Cell wall
– mesh-like
– diffuse through
• Cell membrane
– transporters
Figure 5.3
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Oxidation/Reduction Reactions
• Reducing power used in
metabolism
– Oxidation
• loss of electrons
– Reduction
• gain of electrons
– reactions linked
Figure 5.5
• one molecule reduced
• one molecule oxidized
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ATP: Biological Energy
• Adenosine
triphosphate
– negative charged
phosphates repel
– high energy bonds
hold together
– breaking bond to
remove phosphate
releases energy
• ATP
– high energy
• ADP
– low energy
Figure 5.6
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Substrate level phosphorylation
• ADP obtains phosphate
from metabolic
intermediate
– molecule which has a
high energy bond
• ATP is formed
Figure 5.7
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Glycolysis
• Start
– 6-carbon sugar
(glucose)
• Energy input
– two phosphorylations
– 2 ATP used for each
glucose
• Cleave
– two 3-carbon
molecules
Figure 5.9
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Glycolysis
• Reductions
– two NAD+ are reduced
– produce electron
carriers
• Substrate level
phosphorylation
– 2 ATP produced for
every glucose
Figure 5.9
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Glycolysis
• Dehydration
– water removed
• Substrate level
phosphorylation
– 2 more ATP produced
• End products
– 2 pyruvates
– 3-carbon molecules
Figure 5.9
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Tricarboxylic Acid Cycle
• TCA or Krebs cycle
• Cycle
– intermediates change
from one form to
another
• Converts Pyruvate to
– CO2
– Reducing power
• NADH
• FADH2
• used in electron transport
for additional ATP
synthesis
– ATP
Figure 5.10
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Pentose Phosphate Pathway
• Production of necessary
precursors
– Ribose-5-phosphate
– Erythrose-4-phosphate
• Production of electron
carriers
– NADPH
Figure 5.11
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Chemiosmosis
• Electron transport chain
• Generating a Proton gradient
– protons pumped across membrane
– occurs as electrons are transported from one
carrier to another
– high concentration outside of membrane
Figure 5.8
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Chemiosmosis
• Generating ATP
– Gradient drives ATPase
• synthesis of ATP from ADP and phosphates
– Electron acceptor drives electron transport
• Oxygen (aerobic respiration)
• Sulfates, Nitrate, Fumarate (anaerobic respiration)
Figure 5.8
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Biosynthesis
• Construct small molecules
– Building blocks for macromolecules
• Uses products of catabolism
– Precursor metabolites
– ATP
– Reducing power
Figure 5.12
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Polymerization and Assembly
• Formation of
macromolecules
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–
–
–
–
DNA
RNA
Proteins
Polysaccharides
Peptidoglycan
• Assembly of cellular
structure
– Self-assembly—
spontaneous
– Enzyme-catalyzed
Figure 5.13
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Anaerobic metabolism
• Anaerobic respiration
– Electron transport
– Final electron acceptor other than oxygen
• Fermentation
– Substrate-level phosphorylation
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Fermentation
• No chemiosmosis
• Energy from
glycolysis
• Conversion of
pyruvate to other
product
– lactic acid
– ethanol
– mixed acids
Figure 5.14
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Classification by nutrition
• Heterotrophs
– Definition: Different feeders
– Organic compounds as source of carbon
• Autotrophs
– Definition: self-feeders
– CO2 as source of carbon
• Chemotrophs
– Definition: chemical feeders
– Energy and reducing power from chemical reactions
• Phototrophs
– Definition: light feeders
– Energy and reducing power from light energy
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Photosynthesis
• Synthesis of
precursor
metabolites
• From CO2
• Calvin-Benson
Cycle
Figure 5.15
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Photosynthesis
• Anoxygenic
photosynthesis
– Cyclic
photophosphorylation
– light energy activates
electron
– electron transport chainproton gradient
– produces ATP
Figure 5.16
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Photosynthesis
• Oxygenic photosynthesis
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–
–
–
Noncyclic
two levels of electron activation by light
water is source of electron
results in O2 production
Figure 5.17
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Regulation of metabolism
• Purpose
– Ensure optimal amount of end products
– Increase cell’s efficiency
• Types of Metabolic regulation
– Enzyme regulation
• Gene regulation
• Activity regulation
– allosteric activation
– feedback inhibition
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Enzyme regulation
• Allosteric activation
– product binds
enzyme at
allosteric site
– inactivates
enzyme
Figure 5.18
Figure 5.20
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Enzyme regulation
• Feedback inhibition
– multiple steps in
metabolic pathway
– end product inhibits
enzyme earlier in
pathway
Figure 5.17
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