Lecture 3. Energy Metabolism

Bacterial Growth and Energy Metabolism Bacterial Growth How to measure bacterial growth 1. CFU (colony forming unit) How to measure bacterial growth 2. Petroff-Hausser counting chamber How to measure bacterial growth 3. Optical density Indirectly estimating the number of bacteria by measuring...

Bacterial Growth and Energy Metabolism Bacterial Growth How to measure bacterial growth 1. CFU (colony forming unit) How to measure bacterial growth 2. Petroff-Hausser counting chamber How to measure bacterial growth 3. Optical density Indirectly estimating the number of bacteria by measuring the turbidity of biological cultures using a spectrophotometer. Bacterial growth curve Lag phase: A period during which the microorganisms adapt to a new environment, synthesizing enzymes and intermediate metabolites. The duration of the lag phase varies depending on the type of bacteria and the medium used. The growth rate of the bacteria is 0, meaning that bacterial proliferation does not occur. Bacterial growth curve Exponential phase: - New cellular components are produced at a constant rate, leading to cell proliferation. - During this phase, the chemical and physiological characteristics of the bacteria are uniform. - Therefore, this phase is used for biological and physiological studies of bacteria. - Nutrient depletion begins gradually, and toxic metabolic byproducts accumulate. - The growth rate per unit time remains constant. Stationary phase: - During the stationary phase, the depletion of nutrients and the accumulation of toxic substances from the exponential phase result in a decrease and cessation of cell growth and proliferation. - The rates of cell proliferation and death are similar, so the growth rate is 0. Death phase: - Due to the complete depletion of nutrients and the increase in large amounts of toxins, microorganisms die off. - The rate of death during this phase is similar to the exponential phase. 미생물의 생장의 차이 Generation : The interval for the formation of two cells from one Generation time : The time required for this to occur Keywords: Metabolism (Catabolism vs. Anabolism) Enzymes Oxidation/Reduction Glycolysis Substrate-level phosphorylation Fermentation TCA cycle Electron Transport System ATP synthase  2H2 O2 2H2O Chemistry Biology Oxidation losing electron losing hydrogen atom Reduction gaining electron gaining hydrogen atom C6H12O6 + 6O2 → 6CO2 + 6H2O ΔGo‘= -2880 kJ/mol Metabolism is mediated by Enzymes. Enzyme: Biocatalysis activation energy Energy The energy, released in redox reactions, is conserved in the formation of certain compounds that contain energy-rich phosphate bonds. Glycolysis C6H12O6 + 2ADP + 2PO43- + 2NAD+ → 2C3H3O3 (pyruvate) + 2ATP + 2NADH + 2H+ + 2H2O Glycolysis: - 2 molecules of pyruvate produced from one molecular of glucose - 2 ATP and 2NADH produced - No CO2 produced - Occurs in cytoplasm Glycolysis Substrate-level phosphorylation 1,3-Bisphosphoglycerate, phosphoenolpyruvate: High energy phosphate groups Regulation of glycolysis TCA cycle 2C3H3O3(pyruvate) +2ADP + 2Pi +8NAD+ + 2FAD + 4H2O → 6CO2 + 2ATP + 8NADH + 2FADH2 TCA(tricarboxylic acid) cycle, citric acid cycle, Krebs cycle One molecule of pyruvate → 3 molecules of CO2 4 molecules of NADH, 1 molecule of FADH2, 1 molecule of ATP  Acetyl-CoA is fully oxidized to CO2. Only one ATP (or GTP) is produced Succinyl-CoA synthetase Regulation of TCA cycle - Most enzymes are deactivated, when ATP is abundantly present. - Isocitrate dehydrogenase is activated by ADP. - Some enzymes are deactivated by NADH. - Expression of TCA cycle genes are suppressed under anaerobic conditions. Fermentation - Energy is generated by glycolysis. - 2 ATP per 1 glucose - NADH should be oxidized while fermentation end-products are produced. - Important for food industry. Ethanol Fermentation Electron transport system ; three major functions in bacterial cell wall Electron transport system Generation of the proton motive force during aerobic respiration FMN, flavoprotein; FAD, flavin adenine dinucleotide; Q, quinone; Fe/S, iron sulfur protein; Cyt, cytochromes; Complex I, NADH:quinone oxidoreductase Complex II, Succinate dehydrogenase Complex III, Cytochrome bo quinol oxidase Complex IV, Cytochrome c oxidase Results of Electron transport system ATP synthesis F0 subunit: Sensitive to oligomycin Structure and function of ATP synthase (Complex V). https://www.youtube.com/watc h?v=LQmTKxI4Wn4