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Chapter 5 Microbial Metabolism

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Enzymes catalyze reactions by lowering the of the reaction. Without enzymes reactions would still occur but rate would be very slow. Ch 5 ... – PowerPoint PPT presentation

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Title: Chapter 5 Microbial Metabolism


1
Chapter 5 Microbial Metabolism
  • Harvesting energy
  • Principles of metabolism
  • Redox reactions
  • ATP
  • Enzymes
  • Glycolysis
  • Transition step
  • TCA cycle
  • Respiration
  • Fermentation
  • Catabolism of non-glucose compounds
  • Photosynthesis

2
Bacterial Metabolism is important to us
  • Clostridium acetobutylicum metabolic waste
    products are acetone and butanol
  • Lactococcus and Lactobacillus added to milk and
    cheese
  • Metabolic processes unique to prokaryotes ?
    potential antimicrobial targets

3
The Complexity of Metabolism!
4
Energy the power to do work
  • Cells do not create energy but convert energy to
    useful forms
  • energy gained by
    breaking the bonds of a compound
  • Cells release energy from compounds

  • release energy

  • require energy input

5
Cellular Metabolism
6
Metabolic Pathway a series of chemical reactions
  • If one metabolic step is blocked ?
  • Specific enzymes facilitate each step

7
Metabolic pathways may be cyclical
8
Oxidation-Reduction (Redox) Reactions
  • Harvesting energy requires series of coupled
    oxidation-reduction reactions ?
  • During catabolism electrons transferred from
  • Reduced electron carriers
    ? bonds contain a form of usable energy

9
Redox Reactions
  • Lose an electron
  • Lose a hydrogen
  • Gain an oxygen
  • Gain an electron
  • Gain a hydrogen
  • Lose an oxygen

10
Electron Carriers
  • Electrons ultimately transferred to terminal
    electron acceptor

11
Electron Carriers NADH, NADPH and FADH2
Reduced NADH
Oxidized NAD
Oxidized NAD
12
ATP
  • Recall ATP
  • ATP contains high-energy phosphate bonds

13
The formation and breakdown of ATP
14
ATP Synthesis 3 ways to make ATP

  • use chemical energy
    released from an exergonic reaction to make ATP

  • use energy from proton motive force
    (created by an electrochemial gradient) to make
    ATP

  • use energy from the sun to drive formation
    electrochemical gradient ? drives formation of
    proton motive force

Substrate-level phosphorylation
15
Enzymes
  • Enzymes neither consumed nor permanently changed
    during a reaction
  • Enzymes catalyze reactions by lowering the
    of the
    reaction
  • Without enzymes reactions would still occur but
    rate would be very slow

16
Enzymes reduce the activation energy of a reaction
17
Induced-fit model of enzyme-substrate interaction
18
The process of enzyme action
Substrate (Fructose 1,6-bisphosphate)
P
1
19
Enzymes dont always work alone
  • any non-protein component
    that assists an enzyme
  • organic cofactors that
    assists an enzyme
  • One coenzyme may assist many different enzymes
  • Most coenzymes synthesized from vitamins

20
Environmental Influence on Enzymes
  • Enzymes have
  • Temperature, pH, salt concentration
  • may grow in extreme
    environmental conditions
  • May require high salt, acid, near-boiling
    temperatures

Boiling Hot Spring
Optimum Temperature
Optimum pH
21
Enzyme Inhibition
  • Inhibitors may be used as antimicrobials
  • Always reversible with enough substrate
  • Ex. sulfa antibiotics bind an enzyme in the folic
    acid synthesis pathway ? inhibit enzyme activity
  • May be reversible or irreversible
  • Ex. mercurochrome (antimicrobial containing
    mercury) oxidizes amino acid cysteine so
    proteins can no longer function

22
Competitive Inhibition
Figure 5.10
23
Allosteric Regulation

  • regulatory molecule that binds to enzyme outside
    of active site and changes enzyme activity
  • - Can

24
How is enzyme activity regulated in a pathway?
  • end product of
    pathway allosterically inhibits enzyme earlier in
    pathway
  • ? enzyme can be activated when end product levels
    drop

25
Figure 5.12
26
Enzyme Inhibition
27
Burning glucose ? getting energy
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