Microbial Metabolism

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Microbial Metabolism

• Chapter 5

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Metabolism - all of the chemical reactions within
a living organism

• 1. Catabolism ( Catabolic )
• breakdown of complex organic molecules into
  simpler compounds
• releases ENERGY
• 2. Anabolism ( Anabolic )
• the building of complex organic molecules from
  simpler ones
• requires ENERGY

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Enzymes - catalysts that speed up and direct
chemical reactions

• A. Enzymes are substrate specific
• Lipases Lipids
• Sucrases Sucrose
• Ureases Urea
• Proteases Proteins
• DNases DNA

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Enzyme Specificity can be explained by the Lock
and Key Theory
E S -----gt ES ------gt E P
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Naming of Enzymes - most are named by adding
ase to the substrate

• Sucrose Sucrase
• Lipids Lipase
• DNA DNase
• Proteins Protease
• removes a Hydrogen Dehydrogenase
• removes a phosphate phosphotase

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Naming of Enzymes

• Grouped based on type of reaction they catalyze
• 1. Oxidoreductases oxidation reduction
• 2. Hydrolases hydrolysis
• 3. Ligases synthesis

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Enzyme Components 2 Parts 1. Apoenzyme -
protein portion 2. Coenzyme (cofactor) -
non-protein
Holoenzyme - whole enzyme
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Coenzymes

• Many are derived from vitamins
• 1. Niacin
• NAD (Nicotinamide adenine dinucleotide)
• 2. Riboflavin
• FAD (Flavin adenine dinucleotide)
• 3. Pantothenic Acid
• CoEnzyme A

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Factors that Influence Enzymatic Activity
Denaturation of an Active Protein
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Inhibitors can effect enzymatic activity 1.
Competitive Inhibitors 2. Noncompetitive
Inhibitors
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Competitive Inhibitors -compete for the active
site

• 1. Penicillin
• competes for the active site on the enzyme
  involved in the synthesis of the pentaglycine
  crossbridge
• 2. Sulfanilamide (Sulfa Drugs)
• competes for the active site on the enzyme that
  converts PABA into Folic Acid
• Folic Acid - required for the synthesis of DNA
  and RNA

Selective Toxicity
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Non-competitive Inhibitors - attach to an
allosteric site
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Energy Production

• 1. Oxidation
• refers to the loss of Hydrogens and or electrons
• 2. Reduction
• the gain of Hydrogens and or electrons

NAD Cycle
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Carbohydrate Catabolism

• Microorganisms oxidize carbohydrates as their
  primary source of energy
• Glucose - most common energy source
• Energy obtained from Glucose by
• Respiration
• Fermentation

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Aerobic Cellular Respiration

• Electrons released by oxidation are passed down
  an Electron Transport System with oxygen being
  the Final Electron Acceptor
• General Equation
• Glucose oxygen----gt Carbon dioxide water
• ATP

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Chemical Equation

• C6H12O6 6 O2 -------gt 6 CO2 6 H2O
• 38 ADP 38 P 38 ATP

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Aerobic Cellular Respiration

• 4 subpathways
• 1. Glycolysis
• 2. Transition Reaction
• 3. Krebs Cycle
• 4. Electron Transport System

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1. Glycolysis (splitting of sugar)

• Oxidation of Glucose into 2 molecules of Pyruvic
  acid
• Embden-Meyerhof Pathway
• End Products of Glycolysis
• 2 Pyruvic acid
• 2 NADH2
• 2 ATP

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2. Transition Reaction

• Connects Glycolysis to Krebs Cycle
• End Products
• 2 Acetyl CoEnzyme A
• 2 CO2
• 2 NADH2

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3. Krebs Cycle (Citric Acid Cycle)

• Series of chemical reactions that begin and end
  with citric acid
• Products
• 2 ATP
• 6 NADH2
• 2 FADH2
• 4 CO2

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4. Electron Transport System

• Occurs within the cell membrane of Bacteria
• Chemiosomotic Model of Mitchell
• 34 ATP

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How 34 ATP from E.T.S. ?3 ATP for each NADH22
ATP for each FADH2

• NADH2
• Glycolysis 2
• T. R. 2
• Krebs Cycle 6
• Total 10
• 10 x 3 30 ATP

• FADH2
• Glycolysis 0
• T.R. 0
• Krebs Cycle 2
• Total 2
• 2 x 2 4 ATP

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Total ATP production for the complete oxidation
of 1 molecule of glucose in Aerobic Respiration

• ATP
• Glycolysis 2
• Transition Reaction 0
• Krebs Cycle 2
• E.T.S. 34
• Total 38 ATP

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Anaerobic Respiration

• Electrons released by oxidation are passed down
  an E.T.S., but oxygen is not the final electron
  acceptor
• Nitrate (NO3-) ----gt Nitrite (NO2-)
• Sulfate (SO24-) ----gt Hydrogen Sulfide
  (H2S)
• Carbonate (CO24-) -----gt Methane (CH4)

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Fermentation

• Anaerobic process that does not use the E.T.S.
  Usually involves the incomplete oxidation of a
  carbohydrate which then becomes the final
  electron acceptor.
• Glycolysis - plus an additional step

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Fermentation may result in numerous end products
1. Type of organism 2. Original substrate 3.
Enzymes that are present and active
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1. Lactic Acid Fermenation

• Only 2 ATP
• End Product - Lactic Acid
• Food Spoilage
• Food Production
• Yogurt - Milk
• Pickles - Cucumbers
• Sauerkraut - Cabbage
• 2 Genera
• Streptococcus
• Lactobacillus

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2. Alcohol Fermentation

• Only 2 ATP
• End products
• alcohol
• CO2
• Alcoholic Beverages
• Bread dough to rise
• Saccharomyces cerevisiae (Yeast)

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3. Mixed - Acid Fermentation

• Only 2 ATP
• End products - FALSE
• Escherichia coli and other enterics

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Propionic Acid Fermentation

• Only 2 ATP
• End Products
• Propionic acid
• CO2
• Propionibacterium sp.

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Fermentation End Products
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Lipid Catabolism
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Protein Catabolism
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Photosynthesis - conversion of light energy from
the sun into chemical energy

• Chemical energy is used to reduce CO2 to sugar
  (CH2O)
• Carbon Fixation - recycling of carbon in the
  environment (Life as we known is dependant on
  this)
• Photosynthesis
• Green Plants
• Algae
• Cyanobacteria

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Chemical Equation

• 6 CO2 6 H2O sunlight -----gt C6H12O6 6
  O2
• 2 Parts
• 1. Light Reaction
• 2. Dark Reaction

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Light Reaction

• Non-Cyclic Photophosphorylation
• O2
• ATP
• NADPH2
• Light Reaction (simplified)

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2. Dark Reaction
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