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