生物體中所有化學反應之總和

1、Chapter 5Microbial metabolism1I. Catabolic and anabolic reactionsMetabolism : 生物體中所有化學反應之總和.Catabolism : degradation (放能)Anabolism : synthesis (吸能)能量反應 : ATPFig. 5.123II. EnzymesEnzymes : biocatalystActivation energySubstrate, product. ex : sucrose glucose + fructoseTurnover number(TON)sucraseEnzyme

2、 活性 : IU, SA4II - 1. Naming enzymes 字尾 ase.分六大類 (Table 5.1)56II - 2. Enzyme componentsApoenzyme + cofactor = holoenzyme cofactor 可為金屬離子 or coenzymeCoenzymes : 多由vitamins 衍生而來. ex : NAD+, NADP+, FMN, FAD, CoA(Table 5.2)Fig. 5.27ex : CoQex : FMN , FADex : NAD+ , NADP+89II - 3. The mechanism of enzymat

3、ic action受質接觸enzyme表面之a(chǎn)ctive site.形成enzyme-substrate complex.Substrate 因其分子之重新排列, 其分子之降解 or 與其他受質之結合而使受質之架構改變.Substrate product, 由 E-S complex被釋放出來.Enzyme 本身未改變, 其可加速化學反應.Fig. 5.3a & 5.3b“ Lock and key model ”“ Induced - Fit model ”10drug11II - 4. Factors influencing enzymatic activityTemerature : d

4、enaturation pHSubstrate conc.InhibitorsFeedback inhibtion(end-product inhibition)Fig. 5.5Fig. 5.4Fig. 5.6Fig. 5.712Temp pHS雙曲線1314NCICI1516II - 5. Ribozymes 如enzyme般具催化功能, 對RNA具專一性.具較小之受質範圍.17III. Energy productionCatabolic reactionATP18III - 1. Oxidation-reduction reactionsOxidation : 失去 e-, reduct

5、ion : 得到e-.Dehydrogenation Fig. 5.8Fig. 5.9192021III - 2. The generation of ATP加入p : phosphorylationThree types : 1. Substrate-level phosphorylation2. Oxidative phosphorylation : ETC3. Photophosphorylation : 只發(fā)生含葉綠體且行光合作用之cell.Fig. 5.1322NAD FAD(FMN) CoQ Cyt O2 H2O23IV. Metabolic pathways of energy

6、productionsBy-products orwaste products24V. Carbohydrate catabolismRespiration & fermentationGlucose 之respiration含 three steps :GlycolysisKrebs cycleETCFig. 5.102526V - 1. GlycolysisTwo stages :Preparatory stageEnergy-conserving stageFig. 5.112728V - 2. Alternatives to glycolsisThe pentose phosphate

7、 pathway(PPP)或稱hexose monophosphate shunt(HMS)形成pentose nucleic acid; glucose; amino acid.產(chǎn)生NADPH.利用此pathway之微生物 : Bacillus subtilis, E.coli, Leuconostoc mesenteroides & Enterococcus faecalis.29The Enter-Doudoroff pathwayG(-) : Rhizobium, Pseudomonas & Agrobacterium. G(+) 則不行pathway.實驗室鑑定Pseudomonas

8、.30V - 3. Cellular respiration definedRespiratory : 物質經(jīng)氧化作用產(chǎn)生ATP之過程, 且其最終之電子接受者為無機物者.Aerobes, anaerobesFig. 5.1031V-3-1 Aerobic respirationThe Krebs cycle = Tricarboxylic acid cycle (TCA cycle) = Citric acid cycle The electron transport chain (ETC)Flavoproteins(Fp)CytochromesUbiquinones(coenzyme Q ;

9、 CoQ)Fig. 5.12Fig. 5.13“ Chemiosomtic mechanism ”323334V-3-2 The chemiosmotic mechanism of ATP generationChemiosmosisProton pumpConcentration gradient, electrical charge gradient, electrochemical gradient, potential energy “proton motive force”ATP synthaseFig. 5.14Fig. 5.15353637V-3-3 A summary of a

10、erobic respirationNADH : 3 ATP, FADH2 (FMNH2) : 2 ATP原核cell : 38 ATP, 真核cell : 36 ATP(Table 5.3)Fig. 5.16383940V-3-4 Anaerobic respiration最終之電子接受者異於氧氣之無機物質, ex : Pseudomonas & Bacillus - 利用 NO3- (nitrogen cycle), Desulfovibrio - SO4-2 H2S (sulfur cycle), 細菌 - CO3-2 CH441V-3-5 Fermentation定義 :由醣類 & a

11、mino acid, organic acids, purines, pyrimidines獲得能量之過程.不需O2參與.不需Krebs cycle & ETC 參與.以有機物質作為最終電子接受者.產(chǎn)生少量ATP, 主要能量貯存於中間產(chǎn)物如lactate & ethanol 中.Fig. 5.1742圖 5.17 發(fā)酵作用。小插圖顯示發(fā)酵作用與整體能量產(chǎn)生之關係。(a) 發(fā)酵作用，第一步驟為糖酵解作用，葡萄糖被分解為丙酮酸。第二步驟中，由糖酵解作用所產(chǎn)生之還原態(tài)輔酶及其相關物質 (如NADH, NADPH) 提供電子及質子給丙酮酸以形成發(fā)酵產(chǎn)物。(b)不同發(fā)酵作用之終產(chǎn)物。於發(fā)酵作用中、ATP

12、只於糖酵解作用中產(chǎn)生。43V-3-5(1) Lactic acid fermentation首要路徑為glycolysis.Glucose 2 pyruvate 2 lactateLactic acid bacteria : Streptococcus & Lcatobacillus 為 homolactic or homofermentative bacteria可導致食品腐敗, 但可生產(chǎn) yogurt, sauerkraut & pickles.無氧Fig. 5.18Fig. 5.114445V-3-5(2) Alcohol fermentationGlucose 2 pyruvate 2

13、 aldehyde + 2 CO2酵母菌(Saccharomyces), 為 heterolactic or heterofermentative bacteria無氧2 ethanolFig. 5.1846474849VI. Lipid catabolismFat : fatty acids + glycerol 微生物可利用lipase將脂肪分解為fatty acids & glycerol TCA cycleFig. 5.205051VII. Protein catabolism微生物利用proteases & peptidases 分解蛋白質為amino acids (A. A.) T

14、CA cycle Deamination : A. A. 之-NH2被移除轉化成 NH4+ Decarboxylation : Dehydrogenation :52VIII. Biochemical testsFermentation : media 含蛋白質, 單一醣類, pH指示劑 & Durham tube.微生物代謝產(chǎn)生之廢棄物, 可被另一 微生物利用為其碳源及能量來源. 如 Acetobacter : yeast ethanol Propionibacterium : lactate pyruvate TCA cycle 代謝過程中產(chǎn)生propionic acid & CO2Swi

15、ss cheese之孔洞即CO2造成Fig. 5.19535455IX. Photosynthesis Phytosynthesis : 將光能 化學能 所產(chǎn)生之能量將CO2 醣類.Phyto - : 陽光 or 光線, synthesis : 合成.利用CO2之碳原子合成醣類亦稱carbon fixation.Cyanobacteria, algae & green plants可行phytosynthesis.Reaction : 6 CO2 + 12 H2O + light energy C6H12O6 + 6 O2 + 6 H2O56Phytosynthesis 可分two stage

16、s : 1. Light reactions or light-dependent reactions : light energy將ADP + Pi ATP, NADPH NADP. 2. Dark reactions or light-independent reactions : 利用ATP之能量及電子將CO2 醣類.57IX-1. The light reaction :photophosphorylation為ATP產(chǎn)生方式之一, only in phytosynthetic cells.利用chlorophyll 並激發(fā)分子中之電子.Green plants, algae & cy

17、anobacteria : chlorophyll a , 位於thylakoids 之膜中.Other bacteria : bacteriochlorophylls被激發(fā)之電子如呼吸作用之ETC, 再藉chemiosmosis自ADP ATP, 在cyclic photophosphorylation, 電子再回到chlorophyll中.58Noncyclic photophosphorylation : 電子並未回到chlorophyll中, 而是與NADPH binding.Chlorophyll 失去之電子由H2O or H2S獲得.產(chǎn)物為 ATP, O2 & NADPH.Fig.

18、 5.23b5960XI-2. The dark reaction : the Calvin- Benson cycle不需light.包括Calvin-Benson cycle pathway.將CO2 醣類.Fig. 5.246162X. A summary of energy production mechanismsPhotosynthetic pigmentsAerobic respiration : O2為最終之電子接受者. anaerobic respiration : NO3- or SO42-. fermentation : 有機物質.Fig. 5.256364X-1. Me

19、tabolic diversity among organismsEnergy source : phototrophs & chemotrophs. Carbon source : autotrophs(CO2, lithotrophs) & heterotrophs(有機物, organotrophs)Energy & carbon source : photoautotrophs, photoheterotrophs & chemoautootrophs.微生物幾乎均為chemoheterotrophs.Fig. 5.266566X-1-1. PhotoautotrophsSource

20、: light, CO2.光合細菌如green sulfur bacteria, purple sulfur bacteria & cyanobacteria, algae, green plants.Reaction 會產(chǎn)生O2, 所以亦稱oxygenic reaction.除cyanobacteria外, 有些原核cell反應不會產(chǎn)生O2, 所以又稱anoxygenic reaction.67Green sulfur bacteria(如Chlorobium : S, sulfideH2S SO42-. or H2 CO2).purple sulfur bacteria(如Chromati

21、um 亦能利用S, sulfide or H2 CO2). 其與green sulfur bacteria最大差別 : chlorophyll 種類& 貯存S之位置不同. 68光合細菌 : bacteriochlorophylls, 吸收較chlorophyll a 為長之light.Green sulfur bacteria之bacteriochlorophylls 於 chlorosomes 之小囊中. purple sulfur bacteria 之 bacteriochlorophylls 於 intracytoplasmic membranes 中.Table 5.66970X-1-

22、2. PhotoheterotrophsEnergy source : sun, 但無法將CO2 醣類.利用有機化合物, 如醇類, 脂肪酸, 有機酸or糖類為C源, 不製造O2.生物如Chloroflexus(green nonsulfur bacteria), Rhodopseudomonas(purple nonsulfur bacteria)71X-1-3. Chemoautotrophs由還原態(tài)之無機化合物獲得energy, 以CO2為C源.Beggiatoa : H2S ; Thiobacillus thiooxidans : S ; Nitrosomonas : NH3 ; Nit