Metabolism
Why Study Metabolism?
• Classification of bacteria
– Oxygen Tolerance
– Biochemical reactions
• Acids, Ammonia, Gases
• Fermentation Products
– Food Products
• Yogurt, Sour Cream, Bread, Alcohol
– Commercial Products
• Citric Acid, Plastics
• Environmental Cleanup
Chapter 5
Ying & Yang of Metabolism
• Metabolism = Anabolism + Catabolism
• Photosynthesis requires Respiration
• Respiration requires Photosynthesis
• Energy Production = Energy
Consumption
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Breakdown
Proteins to Amino Acids, Starch to Glucose
Synthesis
Amino Acids to Proteins, Glucose to Starch
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Overview of Metabolism
• Source of Energy (Photo- vs.
Chemotroph)
– Source of Electrons
– Carrier of Electrons
– Final Electron Acceptor
• Source of Carbon (Auto- vs.
Heterotroph)
– Auto- : Carbon Dioxide
– Hetero- : Organic Compounds
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Classification based on Metabolism
• Where microbes get their energy?
– Sunlight vs. Chemical
– Photo- vs. Chemo- trophs
• How do they obtain carbon?
– Carbon Dioxide (or inorganic cmpds.) vs.
Organic Compounds (sugars, amino acids)
– Auto- vs. Hetero- trophs
• Examples
– Photoautotrophs vs. Photoheterotrophs
– Chemoautotrophs vs. Chemoheterotrophs
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Types of -trophs
Type
Energy
C source
Example
Photoauto-
Sun
CO2
Purple &
Green sulfur
bacteria
Photohetero-
Sun
Organic
Compounds
Purple &
Green Nonsulfur bacteria
Chemoauto-
Chemical
bonds
CO2
H, S, Fe, N
bacteria
Organic
Compounds
Most bacteria,
fungi,
protozoa,
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animals
Chemohetero- Chemical
bonds
Source of Electrons
• Autotrophs
– Photosynthesis
– H2O, H2S
• Chemotrophs
– Organic Compounds
– Carbohydrates (C H2O)
• Glucose, Lactose, Sucrose, Mannitol, Citrate
– Amino Acids
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Electron Carriers
• Photosynthesis
– NADP + H to NADPH
• Respiration
– NAD + H to NADH
– FAD + H to FADH
• Contain Niacin and Riboflavin
– Vitamins, not stable
– Can’t store these molecules
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Final Electron Acceptor
• Photosynthesis
– CO2 + H’s to CH2O
– Stores energy
• Respiration
– Aerobic
• 1/2 O2 + H 2 to H2O
– Anaerobic
• Fermentation
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Movement of Electrons
• Chemical reactions
• Oxidation Reactions
• Reduction Reactions
• Reactions Coupled
– Redox reactions
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Example of Redox Equations
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Example of Redox Equations
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Example of Redox Equations
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Examples
• ATP  ADP + P
– Oxidation, release energy
• ADP + P  ATP
– Reduction, stores energy
•
•
•
•
NAD + H  NADH
FADH  FAD + H
NH4 + 11/2O2 NO2- +H2O + 2H + ATP
2H2 + O2  2H2 O
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Examples
• Cellular Respiration
– C6H12 O6 + 6O2 6H2O + 6CO2 + 38 ATP
• Photosynthesis
– 6H2O + 6CO2 + light  C6H12 O6 + 6O2
• Nitrification
– NH4  NO2 to NO3
• Ammonia to Nitrite to Nitrate
• Ammonification
– N2  NH4
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Respiration
• Overview;
– Glucose to Carbon dioxide + Water
+Energy
– C6H12O6 + O2  6CO2 + 6H2O + 38 ATP
– Glucose is highly reduced; contains energy
– Oxygen receives the electrons to form
energy
• 4 separate reactions
– Glycolysis, Transition Reaction, Krebs
Cycle, Electron Transport, Chemiosomosis
• Requires Oxygen
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Steps in Respiration
• Electron Donors
– Organic Compounds (Glucose preferred)
• Electron Carriers
– NAD to NADH
– FAD to FADH
• Electron Acceptors-Terminal
– O2 to H2O
• Phosphorylation Reactions
– ADP to ATP
• Chemiosmosis Reactions
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Glycolysis- 10 steps
• Glucose is Phosphorylated to form
Fructose 1,6-diphosphate
• Split to form 2 Glyceraldehyde 3phosphate
• Final Products are:
– 2 Pyruvic Acid (C3H4O3)
• Compare to original glucose - C6H12O6
– 2 NADH
– 2 ATP
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Transition Reaction
• Pyruvic Acid  Acetyl - Co A + CO2 +
NADH
• C 2H 4O 2
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Kreb’s Cycle
• Figure E.3, A29
• Acetyl CoA  Carbon Dioxide
– C2H4O2 to CO2
– Energy produced/Acetyl CoA (x2 for
/Glucose)
• 3 NADH
• 1 FADH
• 1 ATP
• Metabolic Wheel
– Fats, amino acids, etc. enter or leave
– Citrate is product of first reaction
• Simmons Citrate Media
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Electron Transport Chain
• NADH oxidized to NAD
• FAD reduced to FADH
• Cytochromes shuffle electrons finally to
O2
– Cytochrome Oxidase important in G - ID
• H2O formed and ATP
• 3 ATP / 1 NADH
• 2 ATP / 1 FADH
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•
Fermentation Products from
Pyruvate
Homolactic = Lactic Acid
– Yogurt, Lactobacillus
•
•
•
•
•
•
Alcohol + CO2
Propionic Acid
Butyric Acid
Acetic Acid
Succinic Acid
Butylene to Acetoin
– basis for VP Test (Vogues-Proskauer)
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Fermentation Products
• Alcohol and Carbon Dioxide
– Yeast mostly
• Lactic Acid
– Humans, muscles without oxygen
– Bacteria (Lactobacillus-yogurt)
• Butyric Acid
– Rancid butter, Clostridium-gangrene
• Acetoin
– Butanediol fermentation in Klebsiella
• Propionic Acid
– Swiss Cheese
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Fermentation in Yeast
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Fermentation in Muscle
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Photosynthesis
• Plants
– CO2 + H2O + Light  C6H12O6 + O2
– Water is split to release electrons
• Bacteria
– H2S is used not water
• Sulfur or Sulfuric Acid formed
• Oxygen not released
– Chlorophyll is different
– Strict Anaerobe
– Purple & Green Sulfur Bacteria
Chapter 5
Chemiosmosis
• Production of ATP in Electron Transport
• Electrochemical Gradient Formed
between membranes
• H+ (Protons) generated from NADH
• Electrical Force (+) & pH Force (Acid)
• Gradient formed
• ATPase enzyme that channels H+ from
High to Low concentration
– 3 ATP/NADH
– 2 ATP/NADH
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Summary of Respiration
• Aerobic Respiration
–
–
–
–
Glycolysis
Transition Rx.
Kreb’s Cycle
Electron Transport
Chain
• Anaerobic
Respiration
– Pyruvate 
• Lactic Acid
• Mixed Acids
• Alcohol + CO2
– Recycle NADH
– 2 ATP / Glucose
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