Title: Chapter 5 Microbial Metabolism
1Chapter 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
2Bacterial 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
3The Complexity of Metabolism!
4Energy 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
5Cellular Metabolism
6Metabolic Pathway a series of chemical reactions
- If one metabolic step is blocked ?
- Specific enzymes facilitate each step
7Metabolic pathways may be cyclical
8Oxidation-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
9Redox Reactions
-
- Lose an electron
- Lose a hydrogen
- Gain an oxygen
-
- Gain an electron
- Gain a hydrogen
- Lose an oxygen
10Electron Carriers
- Electrons ultimately transferred to terminal
electron acceptor
11Electron Carriers NADH, NADPH and FADH2
Reduced NADH
Oxidized NAD
Oxidized NAD
12ATP
- Recall ATP
- ATP contains high-energy phosphate bonds
13The formation and breakdown of ATP
14ATP 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
15Enzymes
- 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
16Enzymes reduce the activation energy of a reaction
17Induced-fit model of enzyme-substrate interaction
18The process of enzyme action
Substrate (Fructose 1,6-bisphosphate)
P
1
19Enzymes 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
20Environmental 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
21Enzyme 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
22Competitive Inhibition
Figure 5.10
23Allosteric Regulation
-
regulatory molecule that binds to enzyme outside
of active site and changes enzyme activity - - Can
24How 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
25Figure 5.12
26Enzyme Inhibition
27Burning glucose ? getting energy