Chapter 13
Lecture Outline
Energetics and Catabolism
Building the Cell

Catabolism
 Breaking

down molecules for energy
Anabolism
 Using
energy to build cell components
 Reducing entropy, creating order

Metabolism
 Balance
between catabolism and anabolism
 Central biochemical pathways used for both

TCA cycle, glycolysis, pentose phosphate shunt
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Metabolism
Sunlight
(Major energy
source today)
Reduced geological
compounds (rocks,
inorganic compounds)
(Reduced) biological
macromolecules (Energy source
for animals)
(starch, fats)
(First energy
source)
Phototrophy
Lithotrophy
Organotrophy
ANABOLISM
CATABOLISM
Energy
Long-term
energy storage
Short-term
energy storage
ATP
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Biosynthesis
Carbon,
nitrogen,
water
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Catabolism Always Generates Heat

Illustrated in microbial composting
Actinomycetes digest wood
and newspaper
Thermophiles take over
compost digestion at 50 -60°C
Refresher

Carbon source for biomass
 Auto Hetero-

Energy source
 Photo Chemo Litho Organo-

Electron source
 Litho Organo-
Phototroph
Only in archaea
Chemotroph
Electron Transfer

Major source of cell energy
 Passage


Requires electron donor, electron acceptor
Electron transport found in all cells
 Different

of electrons releases energy
donors, acceptors
Electron energy can be stored
 Reduced
chemicals
 Concentration gradient
 Phosphorylation of chemicals
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Energy Carriers
ATP
 NADH
 NADPH
 FADH2

Catabolism: The Microbial Buffet

Microbes have great catabolic diversity
 Electron donors
 Lithotrophy: inorganic molecules
Chemotrophy
 Organotrophy: organic molecules
 Phototrophy: use light energy to reduce compounds, then
use these as electron donor
 Electron acceptors
 Respiration: inorganic molecules are terminal electron
acceptors



Aerobic: oxygen
Anaerobis: other inorganic compounds, e.g. nitrate
Fermentation: organic molecules are terminal electron
acceptors
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Organotrophy

Wide range of organic compounds digested
 Polysaccharides

Converted to glucose
 Lipids

Converted to acetyl-CoA

And glycerol
 Amino
acids
 Aromatic compounds

Converted to acetyl-CoA
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Glucose metabolism
Fermentation
Respiration
Glucose Metabolism
Glucose  pyruvate
 Three pathways

 EMP

Many bacteria,
archaea, eukaryotes
 ED

Enteric bacteria
 PPS
Glucose metabolism
Fermentation
Respiration
Fermentation

Completes glucose metabolism
 Glucose

NADH is reduced




Must be reoxidized to NAD+ + H+
Pyruvate product builds up


is oxidized
Must be eliminated
In the absence of oxygen
Pass electrons back to pyruvate or to AcetylCoA produced from pyruvate
Convert pyruvate into other products
 Useful
for cell, or easy to eliminate
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Fermentation Examples

S. cerevisiae (baker’s yeast)
 Decarboxylate

CO2 produced causes bread to rise
 Reduce

buildup, reoxidized when O2 present
E. coli
 Mixed

acetaldehyde to ethanol
Vertebrate muscles
 Lactate

pyruvate
fermentation produces formate, acetate
Propionibacterium
 CO2
produced makes holes
Microbiology: An Evolving Science
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in cheese
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Swiss Cheese (Emmentaler)
Fermentation product of
Propionibacterium freudenreichii
Lactate
Propionate, acetate, and CO2
Glucose metabolism
Fermentation
Respiration
Respiration

Complete oxidation of pyruvate/acetylCoA to CO2
and H2O
 Pyruvate
= glycolysis product
 AcCoA = lipid oxidation product



Utilizes TCA (tricarboxylic acid) cycle
Typically with inorganic electron acceptor
Respiration produces more energy than
fermentation
 Maximal
38 ATPs
 Fermentation up to 2 ATPs

conducted only when no inorganic acceptor present
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Aromatic Catabolism

Bacteria can degrade many compounds
 Pseudomonas,

Rhodococcus
Aromatic compounds converted to pyruvate
 Allows
growth in wide range of environments
 Used for bioremediation
Cleaning up oil spills
 Cleaning industrial sites
 Degrading toxic compounds

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As a Whole Bacteria Can Metabolize
Almost Any Compound
Extracellular
polysaccharides
Bacterium CJ2
Catabolizes the pollutant napthalene
Concept Quiz
What do fermentation and the TCA cycle
have in common?
They both oxidize pyruvate.
b. They both produce energy.
c. They both eliminate waste pyruvate.
a.
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