Bacteria show an incredible diversity with regards to their use of different energy sources'

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Introduction
Bacteria show an incredible diversity with
regards to their use of different energy sources.
An overview of a hypothetical bacterial
cell Substrates Energy conservation (ATP and
transmembrane potential) Biosynthesis Transport Mo
vement Cell division
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Energy and Carbon Metabolism An overview
Energy
Chemotrophs
Phototrophs
Chemo-lithotrophs Chemo-organotrophs
Carbon metabolism
Heterotroph
Autotroph (CO2)

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Basic principles
The common denominators in energy metabolism are
ATP and transmembrane potentials
Mechanisms for the generation of ATP Substrate
level phosphorylation Respiration Photophosphoryl
ation
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Adenosine-5'-triphosphate (ATP) Figure 8.3
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Oxidation / Reduction (Redox) reactions
Redox reactions Oxidation is the loss of
electrons and reduction is the gain of electrons.
Electrons cannot exist in solution and the loss
of electrons must be coupled to the gain of
electrons. Reduction potential This is a
quantitqtive measure of the tendency for a
substance to give up electrons in biological
systems. It is measured in volts and generally at
pH 7.0. Half reactions Half reaction are a
convenient way of showing the reduced and
oxidized form of a compound. Two half reactions
are coupled to give a redox reaction.
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Half reactions Table 8.1
The number of electrons transferred (n), and the
electrode potential under standard conditions
(E0') compared to the hydrogen half cell.
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Relationship between free energy and reduction
potential
?Go -nF ? Eh ?Go Change in Free energy n
number of electrons in reaction F Faradays
constant ? Eh E (oxidized) - E (reduced)
ATP hydrolysis releases 31.8 kJ / mole so we
need at least this amount of energy to make a
phosphodiesterase bond in ATP.
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Nicotinamide adenine dinucleotide (NAD)
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Respiration and fermentation
Fermentation Energy generation by anaerobic
energy-yielding reactions characterized by
substate level phosphorylation and the absence of
cytochrome-mediated electron transfer. Respiration
Energy generation in which molecular oxygen or
some other oxidant is the terminal electron
acceptor. Among the latter are nitrate, sulfate,
carbon dioxide and fumarate.
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Energy and Carbon Metabolism Fermentative
organisms
Energy
Chemotrophs
Phototrophs
Chemo-lithotrophs Chemo-organotrophs
Carbon metabolism
Heterotroph
Autotroph (CO2)

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Glycolysis
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Substrate level phosphorylation

• There are three basic reactions. 1 and 2 are
  found in most aerobic and anaerobic bacteria
  which grow on sugars. 3 is found mainly in
  anaerobic fermenting bacteria.
• 1. 1,3 bis-phosphoglycerate ADP
  3 phosphoglycerate ATP
• 2. phosphoenol pyruvate ADP
  pyruvate ATP
• 3. acetyl phosphate AMP
  acetate ATP

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An example of substrate level phosphorylation
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Acetyl-coenzyme A (acetyl-CoA) The thioester
bond between the ß-mercaptoethylamine moiety of
CoA and the acetyl groups () is an energy-rich
bond.
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Stickland reaction
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Respiration and fermentation
Fermentation Energy generation by anaerobic
energy-yielding reactions characterized by
substate level phosphorylation and the absence of
cytochrome-mediated electron transfer. Respiration
Energy generation in which molecular oxygen or
some other oxidant is the terminal electron
acceptor. Among the latter are nitrate, sulfate,
carbon dioxide and fumarate.
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Energy and Carbon Metabolism respiration
Energy
Chemotrophs
Phototrophs
Chemo-lithotrophs Chemo-organotrophs
Carbon metabolism
Heterotroph
Autotroph (CO2)

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Energy transducing membranes
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Components of the electron transport chains
Flavo proteins carry two electrons (e-) and two
protons H) Iron sulphide proteins carry one
electron (e-) Quinones carry two electrons (e-)
and two protons H) Cytochromes carry one
electron (e-)
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Flavin nucleotides, components of flavoproteins
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Iron-sulfur groups, components of nonheme iron
proteins
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Coenzyme Q (ubiquinone)
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The heme portion of a cytochrome molecule
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The electron transport chain operating during
aerobic growth in Paracoccus denitrificans.
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The electron transport chain of Thiobacillus
ferrooxidans, which uses Fe2 as an energy source
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The structure of ATP synthase, showing the F0 and
F1 subunits.
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Diversity
In this lecture I have covered basic themes but
at the begining of the lecture I said something
about metabolic diversity. This diversity is
generated from variation in the electron donor
(organic (thousands to choose from) or inorganic
( a few to chose from)) terminal electron
acceptor organic (fermentation) or inorganic
(respiration). Use of light energy in the
phototrophs.