Microbial MetabolismCh 5 • Metabolism is the sum of the chemical reactions in an organism. • Catabolism is the energy-releasing processes. • Anabolism is the energy-using processes. (typically building something)
Microbial Metabolism • Catabolism provides the building blocks and energy for anabolism. Figure 5.1
Amphibolic pathways • Are metabolic pathways that have both catabolic and anabolic functions. • This is basically all of life Figure 5.32.1
Amphibolic pathways Figure 5.32.2
A metabolic pathway is a sequence of enzymatically catalyzed chemical reactions in a cell. • A primary metabolic pathway are the reactions that do the basic work of the cell. Get food and grow • Metabolic pathways are determined by enzymes. • Enzymes are encoded by genes.
Biochemical tests • Used to identify bacteria. • Enzymes are genes • Sum of genes is your organism Figure 10.8
Enzymes Figure 5.2
Enzymes • Biological catalysts • Specific for a chemical reaction; not used up in that reaction • Apoenzyme: protein • Cofactor: Nonprotein component • Coenzyme: Organic cofactor • Holoenzyme: Apoenzyme + cofactor
Enzymes Figure 5.3
Important Coenzymes • NAD+ • NADP+ • FAD • Coenzyme A • Biotin • Folic acid • Many of the vitamins
Enzymes • The turnover number is generally 1-10,000 molecules per second. Figure 5.4
Factors Influencing Enzyme Activity • Enzymes can be denatured by temperature and pH Figure 5.6
Factors Influencing Enzyme Activity • Temperature Figure 5.5a
Factors Influencing Enzyme Activity • pH Figure 5.5b
Factors Influencing Enzyme Activity • Substrate concentration Figure 5.5c
Factors Influencing Enzyme Activity • Competitive inhibition Figure 5.7a, b
Factors Influencing Enzyme Activity Sulfa inhibits the enzyme that uses PABA for synthesis of folic acid
Factors Influencing Enzyme Activity • Noncompetitive inhibition Figure 5.7a, c
Feedback inhibition Figure 5.8
The Generation of ATP • ATP is generated by the phosphorylation of ADP.
The Generation of ATP • Substrate-level phosphorylation is the transfer of a high-energy PO4- to ADP.
The Generation of ATP • Energy released from the transfer of electrons (oxidation) of one compound to another (reduction) is used to generate ATP by chemiosmosis.
Carbohydrate Catabolism • The breakdown of carbohydrates to release energy • Glycolysis • Krebs cycle • Electron transport chain
Glycolysis • The oxidation of glucose to pyruvic acid, produces ATP and NADH.
Preparatory Stage Preparatory Stage Glucose • 2 ATPs are used • Glucose is split to form 2 Glyceraldehyde-3-phosphate 1 Glucose 6-phosphate 2 Fructose 6-phosphate 3 Fructose 1,6-diphosphate 4 5 Glyceraldehyde 3-phosphate (GP) Dihydroxyacetone phosphate (DHAP) Figure 5.12.1
Energy-Conserving Stage 6 • 2 Glucose-3-phosphate oxidized to 2 Pyruvic acid • 4 ATP produced • 2 NADH produced 1,3-diphosphoglyceric acid 7 3-phosphoglyceric acid 8 2-phosphoglyceric acid 9 Phosphoenolpyruvic acid (PEP) 10 Pyruvic acid Figure 5.12.2
Glycolysis • Glucose + 2 ATP + 2 ADP + 2 PO4– + 2 NAD+2 pyruvic acid + 4 ATP + 2 NADH + 2H+
Alternatives to Glycolysis • Pentose phosphate pathway: • Uses pentoses and NADPH • Operates with glycolysis • Use and production of 5 carbon sugars (na) • Bacillus subtilis, E. coli, Enterococcus faecalis • Entner-Doudoroff pathway: • Produces NADPH and ATP • Does not involve glycolysis • Pseudomonas, Rhizobium, Agrobacterium
Cellular Respiration • Oxidation of molecules liberates electrons for an electron transport chain • ATP generated by oxidative phosphorylation
Intermediate Step • Pyruvic acid (from glycolysis) is oxidized and decarboyxlated Figure 5.13.1
Krebs Cycle • Oxidation of acetyl CoA produces NADH and FADH2
Krebs Cycle Figure 5.13.2
The Electron Transport Chain • A series of carrier molecules that are, in turn, oxidized and reduced as electrons are passed down the chain. • Energy released can be used to produce ATP by chemiosmosis.
Chemiosmosis Figure 5.15
Electron transport and Chemiosmosis Figure 5.16.2
Respiration • Aerobic respiration: The final electron acceptor in the electron transport chain is molecular oxygen (O2). • Anaerobic respiration: The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the Krebs cycles operations under anaerobic conditions.
Energy produced from complete oxidation of 1 glucose using aerobic respiration
ATP produced from complete oxidation of 1 glucose using aerobic respiration • 36 ATPs are produced in eukaryotes.
Fermentation • Releases energy from oxidation of organic molecules • Does not require oxygen • Does not use the Krebs cycle or ETC • Uses an organic molecule as the final electron acceptor
Fermentation Figure 5.18b
Fermentation • Alcohol fermentation. Produces ethyl alcohol + CO2 • Lactic acid fermentation. Produces lactic acid. • Homolactic fermentation. Produces lactic acid only. • Heterolactic fermentation. Produces lactic acid and other compounds.
Fermentation Figure 5.19
Fermentation Production of acid and gas Figure 5.23
Lipid Catabolism Figure 5.20
Protein Catabolism Extracellular proteases Protein Amino acids Deamination, decarboxylation, dehydrogenation Krebs cycle Organic acid
Biochemical tests • Used to identify bacteria. Figure 10.8