Microbial Metabolism

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Chapter 4

• Microbial Metabolism

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Metabolism
Catabolism (????)
Anabolism (????)

• Breakdown of complex organic compounds into
  simpler ones
• Generally hydrolytic reactions (????)
• Exergonic (??)

• Building of complex organic compounds from
  simpler ones
• Involve dehydration synthesis reactions(??/????)
• Endergonic (??)

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Metabolism in perspective
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Enzymes
Catabolism and anabolism are all mediated by
enzymes, which are proteins produced by living
cells that catalyze (??) chemical reactions by
lowering the activation energy (???) required to
start a reaction

• Enzymes have specificity (???)
• Each enzyme catalyzes only one reaction
• Enzymes are very efficient-increase reaction rate
  by 108-1010 times
• Turnover number(???) maximum no. of substrate
  molecules converted to product per second
  (????????????????)

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Enzymatic reaction
Sucrase ???
???
glucose
Sucrose

??
fructose
??
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Enzyme components
??
??
??????
??
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Activation energy
Activation energy amount of energy needed to
disrupt stable molecule so that reaction can take
place
??
??????????
????
?????????
??
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Enzymatic reaction steps
?-?????
????
1. Substrate approaches active site 2.
Enzyme-substrate complex forms 3. Substrate
transformed into products 4. Products
released 5. Enzyme recycled
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Factors Affecting Enzyme Activity
1. Temp 2. pH 3. Substrate concentration 4.
Inhibitors
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Enzyme inhibitor action
Non-competitive Inhibition
Competitive Inhibition
????
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Energy ProductionOxidation-Reduction Reactions
Redox reaction oxidation-reduction pair of
reactions
Oxidation removal of electrons from
molecule Reduction gaining of 1 electrons
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Energy Production
NAD ??????????(??I)
????? ????
NADP ????????????(??II)
??2?H???????
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Energy ProductionATP(?????)
???
??
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Role of ATP in Metabolism
1. ATP is a high-energy molecule a. It breaks
down almost completely b. Removing terminal
phosphate causes large negative change in free
energy c. Releases large amount of energy 2.
ATP is energy currency of the cell 3. ATP has
high phosphate group transfer potential 4. ATP
is a coupling agent in the cell links exergonic
reactions to endergonic reactions
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Energy Production
Three mechanisms of phosphorylation to generate
ATP 1. Substrate-level phosphorylation 2.
Oxidative phosphorylation 3. Photophosphorylation
Substrate level phosphorylation synthesis of
ATP by donation of P on carbon 1 (phosphorylated
organic compound) to ADP.
Oxidative phosphorylation process by which
energy from electron transport is used to make ATP
Photophosphorylation process by which light
energy is used to make ATP
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Carbohydrate Catabolism
Carbohydrate catabolism breakdown of
carbohydrates to produce Energy. There are two
types of carbohydrate catabolism 1
Respiration 2 Fermentation
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Respiration andFermentation
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Glycolysis Initial stage
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Substrate level phosphorylation
Glycolysis ATP producing stage
?1??????4?ATP,????2?ATP,???2?ATP
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Krebs Cycle
Krebs Cycle (TCA cycle, citric acid cycle?????)
series of redox reactions in which potential
energy stored in acetyl CoA (????A)is released
step by step
Krebs cycle produces from every 2 Acetyl CoA 4
CO2 6 NADH 2 FADH2 2 ATP
2 Acetyl CoA 2 carbons each
2 pyruvate 3 carbons each
decarboxylation
FAD ?????????
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Details of Krebs Cycle
When FAD (oxidized form) is reduced, two H atoms
are added directly to produce FADH2 (reduced form)
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Electron Transport Chain
Electron Transport Chain is a series of electron
carriers that transfer electrons from donors
(NADH, FADH2) to electron acceptors (O2)
It is located Bacteria Plasma
membrane Eucaryotes Inner membrane of mitochondria
Oxidative phosphorylation process by which
energy from electron transport is used to make ATP
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Location of electron transport chain in eukaryotes
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Electron Transport Chain
??????
??
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Cytochromes are proteins with iron-containing
porphyrin (heme) prosthetic groups attached to
them
When heme groups (oxidized form) in cyt molecules
are reduced, single electrons are added directly
the central iron atom, converting Fe (oxidized
form) to Fe(reduced form). Heme groups do not
accept protons.
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Electron Transport Chain
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ATP synthase protein complex contains only
channels for proton entry. As protons push in
through channel, the base rotates. Specific
binding sites allow ADP Pi    ATP.
Creation of Proton Motive Force (PMF)
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Electron Transport Chain
Oxidative phosphorylation
1?NADH??3?ATP
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Yield of ATP in Glycolysis Aerobic Respiration
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Glycolytic Pathway(?????) Substrate-level
phosphorylation (ATP) 2 ATP Oxidative
phosphorylation w/ 2 NADH 6 ATP 2 Pyruvate to 2
Acetyl CoA(????????A) Oxidative phosphorylation
w/2 NADH 6 ATP Tricarboxylic Acid Cycle(?????)
Substrate-level phosphorylation (GTP) 2
ATP Oxidative phosphorylation w/ 6 NADH
18 ATP Oxidative phosphorylation w/ 2
FADH2 4 ATP Total 38 ATP
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Anaerobic Respiration
Anaerobic respiration energy-yielding process in
which terminal electron acceptor is oxidized
inorganic compound other than oxygen

• Major electron acceptors Nitrate, sulfate, CO2,
  Iron
• Anaerobic respiration produces less ATP
• Anaerobic respiration is more efficient than
  fermentation
• Uses ETC oxidative phosphorylation in absence
  of O2

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Fermentation
Fermentation energy-yielding process in which
organic molecules serve as both e donors and e
acceptors. It
1. releases energy from organic molecules 2.
does not require oxygen, but sometimes can occur
in its presence 3. does not require use of the
Krebs cycle or ETC 4. uses organic molecule as
final electron acceptor (pyruvic acid or its
derivatives) 5. produces small amounts of ATP 6.
is needed to recycle NAD
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Examples of Fermentation
Alcoholic fermentations ethanol and CO2 Lactic
acid fermentations lactic acid (lactate) Formic
acid fermentation mixed acids or butanediol
ethanol (??) lactic acid (??lactate) mixed acids
(???)or butanediol (???) Formic acid (??/??)
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Fermentation
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Nutritional Patterns
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Nutritional Requirements
1. Photolithotrophic autotrophs photolithoautotro
ph (????) Light Inorganic H source CO2 carbon
source 2. Photoorganotrophic heterotrophs photoorg
anoheterotroph (????) Light energy Organic H
source Organic carbon source 3.
Chemolithotrophic autotrophs chemolithoautotroph
(????) Chemical energy source Inorganic H
source CO2 Carbon source 4. Chemoorganotrophic
heterotrophs chemoorganoheterotroph
(????) Chemical energy source Organic H
source Organic carbon source
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Nutritional Requirements
If an organism uses light as an energy source,
organic substances for an electron source and
organic substances for a carbon source, what is
it called?
Carbon sources Auto Hetero
Energy sources Photo Chemo
Hydrogen sources Litho Organo
Photoorganoheterotroph
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AnabolismMetabolic Pathways of Energy Use
1. Polysaccharide biosynthesis 2. Lipid
biosynthesis 3. Amino acid biosynthesis 4.
Protein biosynthesis 5. Purine pyrimidine
biosynthesis
Primary use of lipids in cells component of
bacterial membranes
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Use of Energy in Biosynthesis
Anabolism the creation of order by the
synthesis of complex molecules from simpler ones
with the input of energy Turnover the
continual degradation and resynthesis of cellular
constituents Most ATP is used in protein
synthesis Anabolism requires a lot of energy
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Construction of Cells
Cells
Organelles(???)
Supramolecular systems
Macromolecules
Monomers
Inorganic molecules