Bacterial Metabolism
Chapter 6
Objectives for today
• This is a big, complicated topic
• What process produces ATP?
• What is the purpose of the Coenzymes?
– Where are these produced?
• How is metabolism different between
prokaryotes and eukaryotes?
Some Definitions
• Electron Carriers:
– Compounds that can accept electrons (and
protons) to drive the production of ATP
– Compounds can easily transfer their electrons
to other molecules
• NAD+, NADP+, FAD
• Reduced form: NADH, NADPH, FADH2
More Definitions
• Redox Reactions (Reduction/Oxidation)
– Oxidation: Loss of electrons
– Reduction: Gain of electrons
• ATP Adenosine Triphosphate
Metabolism
• The sum total of ALL
chemical reactions
within a cell
– Catabolic
• Creates ATP
– Anabolic
• Uses ATP
• Creates other
biomolecules
Energy is the capacity to do work
• Potential energy:
stored energy
• Kinetic energy: energy
of motion
Organisms obtain energy from
different sources
• Photosynthetic organisms obtain energy
from…
• Chemoorganotrophs obtain energy from…..
Chemoorganotrophs
depend on
photosynthetic
organisms
What promotes chemical
reactions in biological systems?
ENZYMES
Enzymes bind substrate and generate a
product, enzyme is unchanged
Some enzymes require a cofactor to bind
substrate
How does this relate to
metabolism?
Coenzymes carry electrons
These are a class of enzymes
Factors that influence an enzyme: Temperature
• What happens as
temperature increases?
• What is the optimum
temperature?
• What would happen if
you put a mesophilic
organism in a
thermophilic
environment?
Factors that influence an enzyme: pH
• What pH do most
enzymes function
optimally?
Enzyme inhibitors
• Inhibit the binding of the substrate to the
active site
– Competitive inhibition
– Non-Competitive Inhibition
Competitive Inhibition
Sulfa drugs can block PABA binding interfering with folic acid
synthesis
Non-competitive Inhibition
Oxidation/reduction reactions
These are especially important for coenzymes
Biological Oxidation
ATP is made in catabolic
reactions and used in anabolic
reactions
Ways cells make ATP
• Substrate level phosphorylation
– Uses energy from breaking down chemicals
– Energy used to add phosphate groups
• Oxidative phosphorylation
– Uses energy from proton motive force
– Uses gradient created in ETS
• Photophosphorylation
– Uses energy created from photons
Types of Bacterial Metabolism
• Fermentation
• Respiration
– Aerobic Respiration
– Anaerobic Respiration
• Photosynthesis
Keep in mind…glucose becomes
many different things
Fermentation
• The incomplete breakdown of glucose with
an organic compound serving as the final
electron acceptor
• Only pathway operating is glycolysis
The big picture:
This process results in
the conversion of 1
glucose molecule into
2 pyruvate molecules
that will be used in the
TCA cycle,
fermentation, etc
Fermentation
Lactic Acid
Ethanol
Lactic Acid Bacteria
Saccharomyces produces ethanol
Fermentation products can vary
Aerobic Respiration
• The COMPLETE breakdown of glucose to
CO2 and H2O with an inorganic compound
serving as the final electron acceptor
Remember the pathways in
aerobic respiration are…
• Glycolysis
– Some use Pentose Phosphate Pathway instead
• TCA cycle
• Electron transport chain
Glycolysis:
Creates Pyruvate
Uses 2 ATP molecules
and you gain 4 (net 2)
This process generates ATP,
FADH2 and NADH with CO2
being the bi-product
http://www.youtube.com/watch?v=WXHpTHb1MQM
What is made as a result of the
TCA cycle?
• ATP
• Reducing power
– NADH, NADPH, FADH2
– Provides Hydrogen gradient in ETC
• Precursor metabolites made from alphaketoglutarate and oxaloacetate
Electron Transport Chain
• Found in the cytoplasmic membrane
• Contains electron carriers
– Flavoproteins (FAD)
• Synthesized from vitamins
– Iron-sulfur proteins
– Quinones
• Lipid soluble electron carriers
– Cytochromes
• Iron centered molecules
Model for energy release in ETC
ETC in eukaryotes
http://www.youtube.com/watch?v=xbJ0nbzt5Kw
http://www.youtube.com/watch?v=3y1dO4nNaKY
ETC in prokaryotes
ATP yield from aerobic respiration
Comparison of three types of
metabolism
Remember we are focusing on
catabolic reactions
• Generate ATP for later use by cell
• Generate precursors for other pathways
• Need to re-oxidize coenzymes for continual
use
Precursor metabolites
Eukaryotes
• ATP production is pretty much the same in
your cells as it is in prokaryotes
– Except all of it is done in the mitochondria
Image Credit: imgkid.com
Summary
• Remember, when we’re talking about
electron transport it’s really about moving
hydrogen ions around to create gradients
• Those gradients are used to create ATP as
ions travel through pours (ATP Synthase)
towards equilibrium