Transcript Microbial Metabolism

Microbial Metabolism
Supplemental instruction
Fall 2010
For Dr. Wright’s Bio 7/27 Class
Designed by Pyeongsug Kim ©2010 [email protected]
Metabolism: try the practice questions. Also, we talked about aerobic respiration, anaerobic respiration, and fermentation. Compare and contrast them as
follows:
Which types of organisms (obligate aerobes, anaerobes, facultative anaerobes, aerotolerant organisms):
Utilize glycolysis (and which can’t)
Utilize the Krebs cycle (and which can’t)
Utilize an electron transport chain/oxidative phosphorylation (and which can’t)
Can use a fermentation pathway (and which can’t)
Which p[athway produces the most ATP? Which produces the least?
Name an electron carrier used in each pathway (for one pathway, there is only one choice)
Metabolism
: All body’s process that transform energy.
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Microbial metabolism
-Chemical reaction used for
biosynthetic and energy-harvesting
process.
-to live and reproduce.
-Components of metabolic pathways
• Energy sources ~ Sunlight, Organic or
inorganic materials
• Enzymes
~ Biological catalyst
~ to facilitate the pathways
• ATP ~ The energy currency of a cell
• Electron donor ~ e- from energy source
• Electron carrier
• Electron acceptor
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Chemical reactions in Metabolism:
Reactants
• Anabolism
A + B + energy
Product

C
Form larger molecules; require energy.
+ energy
• Catabolism

Reactant
C

Products
A + B + energy
Breaking down into smaller molecules; release energy.

+ energy
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Metabolic pathway
- A series of sequential chemical reactions.
Initial compounds  intermediates  end products
- Linear, Branched, Cyclical(eg. TCA Cycle)
Picture from Dr.Wright Bio27 class slide
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For metabolic process, each chemical reaction in a metabolic
pathway needs specific ________.
enzyme
Enzymes
_______
-Biological catalysts
speed up chemical reaction by …
lowering activation energy
-specific; proteins
-sensitive to environmental conditions
pH, Temperature,
Picture from Dr.Wright Bio6 class slide
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Energy source or Electron donor
- The compounds that are oxidized to release ATP.
We inhale oxygen to generate ATP.
-________
Electrons
-donated by the energy source.
-transferred to another compound (electron carrier eg. NAD+, FAD2+).
Microorganisms oxidize carbohydrates(eg. glucose)
as their primary source of energy.
Picture from: http://i.telegraph.co.uk/telegraph/multimedia/archive/01031/news-graphics-2007_1031495a.jpg http://www.biojobblog.com/tags/microbes/
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Energy(or electron) Carriers
- NAD+, NADP+, & FAD “Oxydized form”
- participate ultimately in ATP synthesis
- When electrons are carried…
NADH, NADPH, FADH2  “Reduced forms” or “Reducing power”
Oxydized
form
Reduced
form
Electron
Electron carrier
© Pyeongsug Kim
-___________
NAD+, FAD
generate a proton motive force which can drive ATP synthesis
-___________
NADP+
used in Biosynthesis (eg. Pentose Phosphate Pathway, Photosynthesis)
Terminal electron acceptor
Aerobes – O2
Anaerobes – Inorganic molecules other than O2
Fermenters – Organic molecules
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Precursor metabolites
- metabolic intermediates (links) in anabolic and catabolic
pathway.
e.g. pyruvates, Glucose 6-phosphate, Acetyl-CoA, …
- Used to generate ATP (catabolic)
- Used to synthesize subunits of macromolecules (anabolic)
Picture from: http://i.telegraph.co.uk/telegraph/multimedia/archive/01031/news-graphics-2007_1031495a.jpg
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Three key metabolic pathways
1) Glycolysis
-produce pyruvates.
-produce reducing power.
-produce 6 precursor metabolites
-2 ATPs are produced.
2) Krebs cycle(TCA Cycle)
-require transition step(3carbons  2carbons)
= pyruvates(3C)  acetyl-CoA(2C)
-produce reducing power.
-produce 2 precursor metabolites
-2 ATPs are produced.
3) Respiration or ETC
-oxydative phospholylation
-Uses reducing power
-Terminal electron acceptor(TEA)
: oxygen, nitrate, carbon dioxide or other inorganic molecule, pyruvate
 regenerate electron carriers.
(NADH  NAD+, FADH2 FAD)
-Lots of APTs!!!
Picture from Dr.Wright Bio27 class slide
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Glycolysis
-Occur in _________________.
Cytoplasm(Cytosol)
-Glucose needs to be traped!
 Glucose 6-phosphate
2 pyruvic acids
- produce ____________.
- NAD  NADH (reduced / oxidized).
1C6H12O6  2 Pyruvates
________ + 2 ATP
____ + 2NADH
_______
1glucose + 2NAD + 2ADP + 2Pi
 2 pyruvates + 2NADH + (2H+)+ 2 ATP
- Oxygen required? (Yes / No)
*All cells undergo glycolysis!!!.
-used in aerobic, anaerobic, & fermentation.
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Pentose phosphate pathway
:alteranated glycolysis
- commonly used to make
5-carbon sugars.
-NAPDH(reducing power) produced
for biosynthesis
-Produce 2 precursors
• Mostly 5C-phosphate
used synthesis of nucleotide (nucleic
acids)
• 4C-phosphate
used synthesis of amino acids
-But, no ATP
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After glycolysis…
In presence of oxygen
- Pyruvic acids enter ___________
mitochondria in eukaryotes.
 converted to __________
Acetyl-CoA there.
 Kerbs Cycle(TCA)!
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Kerbs Cycle(TCA)
-Aerobic, anaerobic respiration (but not fermentation)
-Circular pathway
-Completes the oxidation of glucose
-Produce….
Reducing power –NADH, FADH2
2 ATPs & 2 precursors.
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Citric acid cycle = Tricarboxylic acid(TCA) cycle =Krebs cycle
Where does Kerbs Cycle(TCA) occur?
•In Eukaryotic cell… Mitochondria
•In Prokaryotic cell… Cytoplasm
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Glycolysis and Krebs cycle In respiring cells.
Glycolysis
- in all organisms.
- aerobic respiration, anaerobic respiration, fermentation
- produce pyruvates, ATPs.
- reducing power: NADH
Krebs(TCA) cycle
- aerobic respiration, anaerobic respiration
- Convert pyruvate to acetyl-CoA
- more ATPs than glycolysis
- reducing powers: NADH, FADH2
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NADH, FADH2
-RNA coenzyme (derived from Vitamin)
- electron
________________
carrier
-Used to temporarily store energy within the cell
NAD  NADH (Reduced/Oxidized)  Carried to ETC
: at Glycolysis, Krebs cycle
NADH  NAD (Reduced/Oxidized)
: at ETC ( Electron Transport Chain )
*The more reduced = the more energy it holds.
Reduced coenzymes carry high-energy electrons
to proton pumps where ATP is then made( ETC).
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Respiration
-Oxydative phosphorylation or ETC
-used reducing powers(NADH, FADH2) made in glycolysis and TCA.
-ETC(electron transport chain)
~ proton motive force by proton pumps
 drive ATP synthase to produce ATP.
•Aerobic respiration
- oxygen as a TEA
-aerobes, facultative anaerobes(under O2 presence)
-Most efficient at generating ATP
•Anaerobic respiration
- inorganic molecule (not O2) as a TEA
: NO3- (nitrate), (e.g., CO2, S, SO4-, NO3- or NO2-)
-different electron carriers
- Methanogens, sulfur bacteria, …
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Electron transport chains(oxidative-phospholyration)
-Redox reactions; transfer electrons from an electron donor to an
electron acceptor.
-NADH, FADH2 (proton motive force) is used to synthesize ATP.
• In aerobic respiration
Electron carriers ~ NADH, FADH2
Final electron acceptors ~ O2 (Oxygen!)
• In anerobic respiration
Alternative electron carriers
Final electron acceptors ~ inorganic molecules(not O2)
 NO3- (nitrate), (e.g., CO2, S, SO4-, NO3- or NO2-)
Eukaryotes
-In inner mitochondrial membrane
Prokaryotes
-In plasma membrane
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Cellular aerobic respiration (4 step)
Glycolysis  (The transition step)  Krebs cycle (Citric Acid Cycle)
 The electron transport system
Final electron acceptor - oxygen
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Cellular anerobic respiration (4 step)
Glycolysis  (The transition step)  Krebs cycle (Citric Acid Cycle)
 The electron transport system
Final electron acceptor – inorganic molecule (not oxygen!)
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In Eukaryotic cells…
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Picture from http://faculty.irsc.edu/FACULTY/TFischer/micro%20resources.htm
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Fermentation
- Neither aerobic or anaerobic respiration
- incomplete oxidation of a carbohydrate
- Organic molecule(eg.pyruvate) as TEA!!
- facultative anaerobes (under lack of O2 or inorganic molecule )
obligate fermenters (never use O2)
- use Glycolysis and additional step.
- Only 2 ATPs
- NO TCA(Krebs) Cycle! NO ETC!
•Lactic Acid Fermenation
- Food Spoilage
- Food Production
Yogurt from Milk
Pickles, Kimchi
•Alcohol Fermentation
-end product ~ alcohol,CO2
Alcoholic Beverages, Bread…
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Obligate fermenters
- organic molecule as TEA
- get their ATP from glycolysis
- lactic acid bacteria, aerotolerants
Different organisms can ferment
different sugars.
Commercially useful
useful in identification
Picture from Dr.Wright Bio27 class slide, http://www.sciencedaily.com/releases/2006/10/061017091752.htm#
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Identification of fermenter
- Different organisms can ferment different
sugars.
Picture from http://www.mc.maricopa.edu/~johnson/labtools/Dbiochem/kiaa.jpg http://web.clark.edu/tkibota/240/Unknowns/PR_Carb.htm
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Prokaryotes: whole process occurs in cytoplasm.
Since don’t have organelles(mitochondria).
Eukaryotes:
Oxidative decarboxylation of pyruvate (pyruvate  Acetyl-CoA)
is required in process of getting into the mitochondrion (where
Krebs cycle occurs)
Picture from http://www.nslc.wustl.edu/courses/Bio2960/labs/04Microscopy/index.html
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Electron transport chain
-for aerobes; aerobic respiration.
- Oxidative phosphorylation
: NADH, FADH2 (proton motive force) is used to synthesize ATP.
Eukaryotes
Prokaryotes
-In inner mitochondrial membrane -In plasma membrane
Picture from Dr. Wright Bio27 class slides
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Aerobic respiration
- terminal electron acceptor is ______.
oxygen
( most / least) efficient at generating ATP
-Obligate aerobes, Facultative anerobes(if O2 presence)
Anaerobic respiration
- terminal electron acceptor is ____________
inorganic molecule
(e.g., CO2, S, SO4-, NO3- or NO2-, But Oxygen(O2))
( less / most ) efficient than aerobic respiration
-Methanogens, sulfur bacteria, …
Fermentation
- terminal electron acceptor _____________.
organic molecule (e.g. pyruvate)
- Do not use Krebs cycle
(most / least) efficient at generating ATP
-Facultative anerobes(if O2 absent) E.Coli
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Aerobic respiration is the most efficient at generating ATP.
Fermentation is the least efficient at generating ATP.
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Phototrophs
- Photosynthetic(Energy from sunlight)
- Produce sugars(glucose)
 consumed by chemoorganotrophs.
-Photosynthesis
Chemical energy is used to reduce CO2 to
sugar (CH2O)
Carbon Fixation - recycling of carbon in the
environment.
- Oxygenic phototrophs
Green Plants, Algae, Cyanobacteria
- Anoxygenic phototrophs
Archaea, Green bacteria, Purple bacteria
-Primary producers
Picture from Dr.Wright Bio27 class slide, http://www.thedailygreen.com/healthy-eating/eat-safe/xtreme-eating-awards-50060309
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Lithotrophs
-“Rock-Eaters”
- Energy(Electron donor) source from inorganic molecules.
H2, H2S, Fe2+, NH4+
-Use CO2 for carbon (autotrophs) (usually)
- Methanogens
Lithotrophs(archaea) at hydrothermal vents
Iron oxidizing bacteria
some nitrogen fixers
Picture from http://www.nature.com/nature/journal/v417/n6885/full/417137a.html
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Chemoorganotrophs(heterotrophs)
- generate energy by degrading organic compounds.
-Consumers, decomposers.
We are chemooranotrophs.
We are eating organic compounds (made
by phototrophs) to generate ATP.
Picture from Dr.Wright Bio27 class slide, http://www.thedailygreen.com/healthy-eating/eat-safe/xtreme-eating-awards-50060309
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