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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
Ying & Yang of Metabolism
Metabolism = Anabolism + Catabolism
Photosynthesis requires Respiration
Respiration requires Photosynthesis
Energy Production = Energy Consumption
BreakdownProteins to Amino Acids, Starch to Glucose
SynthesisAmino Acids to Proteins, Glucose to Starch
Chapter 5
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
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
Movement of Electrons
Chemical reactions
Oxidation Reactions
Reduction Reactions
Reactions Coupled Redox reactions
Chapter 5
Example of Redox Equations
Final Electron Acceptor
Photosynthesis– CO2 + H’s to CH2O
– Stores energy Respiration
– Aerobic• 1/2 O2 + H 2 to H2O
– Anaerobic• Fermentation
Chapter 5
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
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
Biochemical Pathways of Energy Metabolism
Series of controlled reactions rather than in a single burst.
Chapter 5
Glycolysis- 10 steps
Glucose is Phosphorylated to form Fructose 1,6-diphosphate
Split to form 2 Glyceraldehyde 3-phosphate Final Products are:
– 2 Pyruvic Acid (C3H4O3)
• Compare to original glucose - C6H12O6
– 2 NADH– 2 ATP
Carbohydrate metabolism
Pentose Phosphate Pathway – hexose monophosphate shunt
Operates simultaneously with glycolysis Provides a means for the breakdown of
5 carbon sugars as well as glucose
Carbohydrate Metabolism
EDP is still another pathway for oxidizing glucose to pyruvic acid
Yield 1 ATP
Used by Gram negatives (e.g. Rhizobium, Psuedomonas, Agrobacterium), usually not by Gram positives.
The Pentose Phosphate pathway (hexose monophosphate shunt) is used to metabolize five-carbon sugars; one ATP and 2 NADPH molecules are produced from oxidation of one glucose molecule. Produces intermediates for nucleotide and nucleic acid synthesis, glucose synthesis from CO2 in photosynthesis, and some amino acids.
Chapter 5
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)
Chapter 5
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
Chapter 5
Fermentation in Yeast
Chapter 5
Fermentation in Muscle
Fermentation of Carbohydrates
Glucose Pyruvic Acid fermentation or respiration
Release energy from sugars or other organic molecules such as amino acids, organic acids, purines and pyrimidines
Does not require oxygen Does not require an electron transport
chain
Fermentation of Carbohydrates
Uses an organic molecule as the final electron acceptor
Oth
er F
erm
enta
tion
Pat
hway
s
Oth
er F
erm
enta
tion
Pat
hway
s
Swiss cheese.
Beer, wine, bread.
Flatulence!
LAB & our own muscles.
Fermentation
Products – ethanol and carbon dioxide Brewing and wine making are anaerobic
processes if oxygen is present further oxidation will occur
Respiration
Is an ATP generating process in which chemical compounds are oxidized and the final electron acceptor is almost always an inorganic molecule
Electron transport chain – readily accept electrons from one compound and pass them to another
ATP generated by oxidative phosphorylation
Respiration
Oxidize organic molecules completely to carbon dioxide
ATP yield greater in respiration than in fermentation
Krebs Cycle
As acetyl CoA enters the Krebs cycle, CoA detaches from the acetyl group and then can pick up more acetyl groups for the next Krebs cycle
Series of redox reactions Yield 38 ATP
Protein Catabolism
Require extracellular enzymes – proteases and peptidases
Deaminate amino acids Decarboxylation
Lipid Catabolism
Fats fatty acids + glycerol Requires lipases Convert glycerol into dihydroxyacetone
phosphate Fatty acids catabolized by beta
oxidation
Energy Utilization
Microbes use ATP to provide energy for the transport of substances across plasma membranes
For flagellar motion Biosynthesis of new cell components
Biosynthesis of Polysaccharides
Bacteria synthesize glycogen from adenosine diphosphoglucose – ADPG
Synthesize capsular material
Biosynthesis of Lipids
Microbes synthesize lipids, by uniting glycerol and fatty acids
Structural components of plasma membrane and Gram – cell wall
Lipids serve as storage forms of energy
Biosynthesis of Amino Acids
Required for protein synthesis E. coli – synthesize all the amino acids
they need Other microbes require some preformed
aa from the environment in order to metabolize proteins
Krebs cycle source of precursors for aa
Biosynthesis of Amino Acids
Other sources of precursors are derived from the pentose phosphate pathway and the EDP
AA building blocks for proteins (toxins)
Biosynthesis of Purines & Pyrimidines
Sugars composing nucleotides are derived from either the PPP or the EDP
Aspartic acid, glycine and glutamine play an essential role in the biosynthesis of purines and pyrimidines
The C and N atoms derived from these aa form the backbone of the purines and pyrimidines
Integration of Metabolism
Anabolic and catabolic reactions are integrated through a group of common intermediates
Krebs cycle – operate in both anabolic and catabolic reactions produce intermediates that lead to the synthesis of amino acids, fatty acids and glycerol – amphibolic pathways
Chemo Organic Autotrophs
• Two types – Chemo organic autotroph • Derives their energy from organic compounds and their carbon source from inorganic compounds – Lithoautotrophs • Neither sunlight nor organics used, rather it relies totally on inorganics
Photoautotroph
• Derive their energy from sunlight • Transform light rays into chemical energy • Primary producers of organic matter for heterotrophs • Primary producers of oxygen • Ex. Algae, plants, some bacteria
Chemoheterotrophs
Derive both carbon and energy from organic compounds – Saprobic • decomposers of plant litter, animal
matter, and dead microbes – Parasitic • Live in or on the body of a host
Iron precipitation at near an iron mine: Iron rich (Fe2+) anaerobic waters become oxygenated at the surface
Precipitated iron seeping from an iron bog in Colorado Bog iron ore from Poland
Bog iron ore from coastal Virginia swamps