microbial metabolism chapter 5. metabolism - all of the chemical reactions within a living organism...
TRANSCRIPT
Microbial Metabolism
Chapter 5
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
Enzymes - catalysts that speed up and direct chemical reactions
A. Enzymes are substrate specific• Lipases Lipids• Sucrases Sucrose• Ureases Urea• Proteases Proteins• DNases DNA
Enzyme Specificity can be explained by the Lock and Key Theory
E + S -----> ES ------> E + P
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
Naming of Enzymes
Grouped based on type of reaction they catalyze
1. Oxidoreductases oxidation & reduction
2. Hydrolases hydrolysis
3. Ligases synthesis
Enzyme Components
2 Parts
1. Apoenzyme - protein portion
2. Coenzyme (cofactor) - non-protein
Holoenzyme - whole enzyme
Coenzymes
Many are derived from vitamins
1. Niacin• NAD (Nicotinamide adenine dinucleotide)
2. Riboflavin• FAD (Flavin adenine dinucleotide)
3. Pantothenic Acid• CoEnzyme A
Factors that Influence Enzymatic Activity
Denaturation of an Active Protein
Inhibitors can effect enzymatic activity
1. Competitive Inhibitors
2. Noncompetitive Inhibitors
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
Non-competitive Inhibitors - attach to an allosteric site
Energy Production
1. Oxidation• refers to the loss of Hydrogens and or electrons
2. Reduction• the gain of Hydrogens and or electrons
NAD Cycle
Carbohydrate Catabolism
Microorganisms oxidize carbohydrates as their primary source of energy
Glucose - most common energy source Energy obtained from Glucose by:
• Respiration• Fermentation
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----> Carbon dioxide + water ATP
Chemical Equation
C6H12O6 + 6 O2 -------> 6 CO2 + 6 H2O
38 ADP + 38 P 38 ATP
Aerobic Cellular Respiration
4 subpathways
1. Glycolysis 2. Transition Reaction 3. Kreb’s Cycle 4. Electron Transport System
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
2. Transition Reaction
Connects Glycolysis to Krebs Cycle
End Products:• 2 Acetyl CoEnzyme A
• 2 CO2
• 2 NADH2
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
4. Electron Transport System
Occurs within the cell membrane of Bacteria
Chemiosomotic Model of Mitchell• 34 ATP
How 34 ATP from E.T.S. ?3 ATP for each NADH2
2 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
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
Anaerobic Respiration
Electrons released by oxidation are passed down an E.T.S., but oxygen is not the final electron acceptor
Nitrate (NO3-) ----> Nitrite (NO2-)
Sulfate (SO24-) ----> Hydrogen Sulfide (H2S)
Carbonate (CO24-) -----> Methane (CH4)
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
Fermentation may result in numerous end products
1. Type of organism
2. Original substrate
3. Enzymes that are present and active
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
2. Alcohol Fermentation
Only 2 ATP End products:
• alcohol
• CO2
Alcoholic Beverages Bread dough to rise
Saccharomyces cerevisiae (Yeast)
3. Mixed - Acid Fermentation
Only 2 ATP End products - “FALSE”
Escherichia coli and other enterics
Propionic Acid Fermentation
Only 2 ATP End Products:
• Propionic acid
• CO2
Propionibacterium sp.
Fermentation End Products
Lipid Catabolism
Protein Catabolism
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
Chemical Equation
6 CO2 + 6 H2O + sunlight -----> C6H12O6 + 6 O2
2 Parts:• 1. Light Reaction• 2. Dark Reaction
Light Reaction
Non-Cyclic Photophosphorylation• O2
• ATP
• NADPH2
Light Reaction (simplified)
2. Dark Reaction