微生物的新陈代谢.pptx

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1、 Metabolism in all cells is divided into catabolic(those pathways involved in breakdown of organic molecules for energy and the production of small compounds that may be used for synthesis)and anabolic(pathways involved in synthesis)processes.In all organisms these pathways are balanced as the energ

2、y required for anabolic processes is produced by catabolic pathways.In mammalian cells,energy production has been maximized by the use of oxygen and thus the cell is usually well supplied with energy;however,in microbes this is not always the case.catabolic and anabolic metabolism第1页/共94页 Microbes c

3、an be divided into metabolic classes which relate to the sources of energy they use.The three groups are:1.heterotrophs which utilize organic molecules as a source of energy(these are also called chemoorganotrophs化能有机营养型化能有机营养型);2.phototrophs which obtain energy from light 3.lithotrophs which obtain

4、 energy from inorganic compounds.Carbon(碳素)for cell synthesis is obtained from organic molecules;however,some microbes,including the phototrophs,fix CO2.Microbial metabolic types第2页/共94页 Catabolism Metabolism anabolism complex molecule simple molecules+ATP+H*（Organic material）*H stands for reducing

5、power(还原力)catabolism enzyme complex（分解代谢酶系）anabolism enzyme complex（合成代谢酶系）第3页/共94页 organic material Primary energy sources(最初能源)ray irradiation(light)Chemoheterotrophs reduced inorganic material Phototrophs chemoautotrophsuniversal energy source (通用能源)ATPEnergy metabolism第4页/共94页Section A Heterotro

6、phic pathwaysBiological oxidation is referred to as all the energy-producing oxidative reactions in the living organism.第5页/共94页Definition:A series of energy-producing oxidative reactions occurs in the living cells are called biological oxidation.The process of biological oxidation (生物氧化的过程)1.Remove

7、 of hydrogen(脱氢)2.Transfer of hydrogen(递氢)3.Receive of hydrogen (受氢)Biological oxidation (生物氧化）生物氧化）第6页/共94页Function of biological oxidation(生物氧化的功能)1.Produce energy (产能)2.Produce reducing power H (产还原力)3.Small intermediate metabolites(产小分子中间代谢物)Types of biological oxidation:1.Aerobic respiration (好

8、氧呼吸)2.Anaerobic respiration(厌氧呼吸)3.Fermentation (发酵)第7页/共94页Pathways of removing of hydrogen:(in the case of Glucose)1.EMP(glycosis)2.HMP(pentose phosphate pathway or WD)3.ED(KDPG)4.TCA cycle(citric acid cycle)Removing 第8页/共94页removetransferreceive（or organic or inorganic oxide）（organic or inorganic

9、 deoxide）Four pathways of Hremoving from substrate第9页/共94页 Most microbes utilize the glycolytic（糖酵解）（糖酵解）pathway for the catabolism of carbohydrates such as glucose and fructose.The products of this pathway are pyruvate,which can be further metabolized via the citric acid cycle,forming adenosine 5tr

10、iphosphate(ATP)and the reduced form of nicotinamide adenine dinucleotide(烟酰胺腺嘌呤核苷酸烟酰胺腺嘌呤核苷酸NADH+H+.）This pathway is located in the cytoplasm of microbes and can function in the presence or absence of oxygen.Key notes(2)Glycolysis(EMP pathway)第10页/共94页 The bacterial genera Pseudomonas,Rhizobium（根瘤菌）（

11、根瘤菌）and Agrobacter（农杆菌）（农杆菌）substitute the EntnerDoudoroff pathway for the glycolytic pathway.This pathway is not as efficient in producing energy,with 1 mole of ATP being formed for each mole of glucose metabolized.Key notes(3)The ED pathway第11页/共94页 The pentose phosphate pathway or hexose monophos

12、phate pathway may operate at the same time as glycolysis or the EntnerDoudoroff pathway.This pathway can also operate either in the presence or absence of oxygen.The pentose phosphate pathway is an important source of energy in many microorganisms;however,its major role would seem to be for biosynth

13、esis.The basic outline of this pathway is shown in the Fig.The pathway produces NADPH.Key notes(4)pentose phosphate pathway(HMP)第12页/共94页 The pentose phosphate pathway（戊糖磷酸途径）（戊糖磷酸途径）produces NADPH+H+and sugars(4 C,5 C).These are required for many synthetic reactions.When organisms are growing on a

14、pentose(5 C)sugar,the pathway can be used to produce carbohydrates for cellwall synthesis.Glyceraldehyde3phosphate(三三磷酸甘油醛磷酸甘油醛)formed by the pathway can be used to generate energy by glycolysis or by the EntnerDoudoroff pathway.Key notes(4)pentose phosphate pathway 第13页/共94页 The metabolism of pyruv

15、ate(formed by glycolysis)to CO2 by the citric acid cycle is the major mechanism of ATP generation in the cell and is also an important source of carbon skeletons for biosynthesis.The fully（完整的柠檬酸循环途径的功能）（完整的柠檬酸循环途径的功能）functioning pathway requires oxygen;however,some organisms possess an incomplete c

16、ycle that can function in the presence or absence of oxygen but generates little or no energy.Key notes(5)Citric acid cycle第14页/共94页 Many microbes use EMP pathways,although energy-producing efficiency is low,it has extremely important physiological functions;most aerobic and facultative anaerobic mi

17、crobes use both HMP and EMP pathways.The feature of it is that G can be thoroughly oxidized through EMP and TCA cycle.ED pathway is a microbe specific substitute way replaces EMP in those microbes that lacks the full EMP pathway.第15页/共94页 NADH+H+produced by catabolic reactions such as the citric aci

18、d cycle can be oxidized by the electrontransport pathway in the presence of oxygen.However,in the absence of oxygen,many microbes utilize fermentation reactions to reoxidize NADH+H+.Microbial fermentations are characterized by the end products formed.(微生物所进行的各种发酵微生物所进行的各种发酵,常常是以他们所形成常常是以他们所形成的终产物而命名

19、的终产物而命名)Clostridia(梭菌则通常通过氨基酸发酵梭菌则通常通过氨基酸发酵Stickland反反应形成应形成ATP)are unusual in that they form ATP from the fermentation of ammo acids by the Stickland reaction.Key notes(6)fermentations第16页/共94页 The citric acid cycle is the most efficient mechanism for generating ATP from glucose in the presence of

20、oxygen.For microbes that live in environments where oxygen is absent or only present intermittently,ATP generation is less efficient.(生活在厌氧或间歇供氧环境中的微生物生活在厌氧或间歇供氧环境中的微生物,ATP产生的产生的效率是低的效率是低的)Key notes(7)ATP yields(产率产率)第17页/共94页 The majority of microbes utilize the glycolytic pathway(糖酵解途径糖酵解途径also kn

21、own as the EmbdenMeyerhof pathway)for the catabolism of carbohydrates such as glucose and fructose.This series of reactions occurs in the cytoplasm of microbes and can operate either anaerobically(in the absence of oxygen)or aerobically(in the presence of oxygen).The overall equation for this pathwa

22、y isGlucose+2ADP+2Pi+2NAD+2 pyruvate+2ATP+2NADH+2H+Glycolysis(糖酵解糖酵解)EMP 第18页/共94页第19页/共94页brief figure of EMP pathway2 stages3 products10 reactionsPyrATP consuming ATP producing第20页/共94页1.Pyruvate formed by glycolysis can be further metabolized in the presence of oxygen to generate energy via the c

23、itric acid cycle or can be used for synthesis of other compounds such as amino acids.2.Adenosine triphosphate(ATP)can be used directly to drive uptake of substrates or can be used to drive synthetic reactions.3.NADH+H+can be used to produce energy via oxidative phosphorylation(a method of ATP format

24、ion that requires electron transport)or can be used as a source of H+for reduction reactions.The product of EMP pathway第21页/共94页 Some organisms such as the bacteria Clostridia utilize inorganic pyrophosphate(无机焦磷酸盐)(PPi)in place of ATP as a source of energy to drive the formation of pyruvate from ph

25、osphoenolpyruvate(磷酸烯醇式丙酮酸)and for the conversion of fructose6phosphate into fructose1,6bisphosphate.Exception 第22页/共94页 A minority of bacteria including Pseudomonas,Rhizobium and Agrobacter substitute the EntnerDoudoroff pathway for the glycolytic pathway.The pathway yields 1 mole each of ATP,NADPH

26、+H+and NADH+H+for each mole of glucose metabolized.The products of this pathway,like those of glycolysis,can be used for a variety of functions;however,the NADPH+H+formed is used for synthetic reactions.ED pathway第23页/共94页ED pathway第24页/共94页ethanolPyrBrief pattern of ED pathway In the presence of ox

27、ygen via respiratory pathway fermentation while avoid of oxygenThrough only 4 steps from G第25页/共94页Characteristics of ED pathway:1.FeatuKDPGred by the reaction that KDPG was catalyzed into pyruvate and glyceraldehyde-3-phosphate.2.Characterized by an special enzyme KDPG醛缩酶醛缩酶3.Two molecules of pyruv

28、ates came from different pathways.4.Low energy-yielding efficiency 1mol ATP/1 mol G第26页/共94页The pentose phosphate pathway or hexose monophosphate pathway(己糖单磷酸途径己糖单磷酸途径)may operate at the same time as glycolysis or the EntnerDoudoroff pathway.This pathway can also operate either in the presence or a

29、bsence of oxygen.The pentose phosphate pathway is an important source of energy in many microorganisms;however,its major role would seem to be for biosynthesis.HMP pathway第27页/共94页Breif pattern of HMP pathway After a series of reactions,hexose were synthesized again第28页/共94页 The basic outline of thi

30、s pathway is shown in Fig.The pathway produces NADPH and sugars(4C,5C),which are required for the synthesis of aromatic amino acids and nucleotides.When organisms are growing on a pentose(5 C)sugar,the pathway can also be used to produce carbohydrates for cellwall synthesis.Glyceraldehyde3phosphate(

31、3磷酸甘油磷酸甘油醛醛)can be used to generate energy via the glycolytic/EntnerDoudoroff pathways.第29页/共94页 Although energy is obtained from the breakdown of pyruvate by one of the previous pathways,a significantly greater yield can be achieved in the presence of oxygen from the further oxidation of pyruvate t

32、o CO2 via the citric acid cycle also known as the tricarboxylic acid cycle.Pyruvate does not enter this pathway directly,it must first undergo conversion into acetyl coenzyme A(acetyl CoA):Pyruvate+NAD+CoA Acetyl CoA+NADH+H+This reaction is catalyzed by pyruvate dehydrogenase,a large complex contain

33、ing three enzymes.Citric acid cycle(TCA)第30页/共94页 Acetyl CoA can also be produced by the catabolism of lipids and amino acids as well as a wide range of carbohydrates.ATP can be formed from NADH+H+by oxidative phosphorylation.This pathway is also an important source of carbon skeletons for use in bi

34、osynthesis.Citric acid cycle enzymes are widely distributed in most microbes and other microorganisms.Functional and complete cycles are found in most aerobic microbes,algae,fungi and protozoa;however,in facultative organisms(兼性微生物兼性微生物those that can grow in the presence or absence of oxygen)the com

35、plete citric acid cycle would only be functional in the presence of oxygen.Many anaerobic organisms have an incomplete cycle,which is used for the production of synthetic precursors.第31页/共94页TCA cycle第32页/共94页12ATP2ATPRespiratory chainRespiratory chain（substrate level）ATPMajor products of TCA cycle第

36、33页/共94页carbohydratesfatproteinThe critical status of TCA cycle in the catabolic and anabolic metabolism第34页/共94页How 38 ATP is formed from 1 glucose via EMP and TCA？is EMP，is TCA，is repiration chain，framed is final product第35页/共94页Characteristics of TCA ctycle:1.Functioning only aerobically(in the p

37、rescence of oxygen),although O2 isnt directly involved in.2.High energy yielding efficient with 4 mole of NADH+H+,1 mole of FADH2 and 1 mole of GTP were formed from 1 mole of pyruvate,equally 15 mole ATP.3.Located in a critical and connecting point between catabolic and anabolic metabilism.第36页/共94页

38、substrate level net ATP 2（about 6 ATP）12（about 36ATP）1（about 3ATP）1（about 3ATP）2（about 2ATP）2+8*（about 30ATP）2（about 4 ATP）Energy-yielding efficient of glucose via different dehydrate pathways第37页/共94页Section B Electron transport and oxidative phosphorylation第38页/共94页 NADH+H+and FADH2 formed by cata

39、bolic reactions are used to produce ATP by the action of an electron-transport chain which is composed of a series of electron carriers.In bacteria,electron transport occurs in the inner cell membrane(细胞质内膜).In other microbes(eukaryotes),electron transport occurs in the inner membrane of the mitocho

40、ndria.Most bacterial electron-transport chains are branched unlike those in mammalian mitochondria.Key notes:electron-transport chain第39页/共94页 All electron-transport pathways function in a similar manner,requiring a series of oxidation and reduction reactions.The oxidation of a molecule involves the

41、 loss of electrons,and reduction involves the addition of electrons.Since electrons are conserved in chemical reaction,oxidations must be coupled with reduction reactions(redox reactions).第40页/共94页 The oxidation-reduction potential(redox potential)of a compound is a measure of its affinity for elect

42、rons.The difference in redox potential between NADH+H+/NAD and 1/2O2/H2O drives the movement of electrons through a series of electron carriers from NADH+H+to 02.Energy is released as electrons move between carriers.This can also be linked to ATP formation.第41页/共94页The chemiosmotic hypothesis(化学渗透学说

43、)is a widely accepted theory that explains how ATP is produced by electron transport.ATP production requires that H+move across the membrane where electron transport occurs,producing a transmembrane H+gradient.The H+moves back across the membrane via ATP synthase.The movement of H+is coupled with la

44、rge releases of energy associated with electron transport,such that when NADH+H+is the electron donor and oxygen is the terminal electron acceptor,H+movement across the membrane occurs at three sites.In microbes with short pathways or where NADH+H+is not the electron donor,less ATP is produced.Forma

45、tion of ATP 第42页/共94页第43页/共94页 NADH+H+and flavin adenine dinucleotide(reduced form)(FADH2)formed by the catabolism of organic molecules are used to produce ATP by the action of an electron-transport chain that is composed of a series of electron carriers which transfer electrons to a terminal electr

46、on acceptor such as oxygen.This final reduction is performed by a terminal oxidase.Oxygen is not the only useful electron acceptor.1.Electron-transport chain(1)第44页/共94页In bacteria,electron transport occurs in the inner cell membrane,but in algae,fungi and many protozoa,electron transport and oxidat

47、ive phosphorylation occur in the inner membrane of the.mitochondria.1.Electron-transport chain(2)第45页/共94页 Most bacterial electron-transport chains are different to that found in mammalian mitochondria and many like E.coli are branched.Some chains are short and this reduces their capacity for ATP pr

48、oduction.Electrons can enter bacterial electron-transport chains at various points and this increases the number of substrates that can be used for ATP synthesis.1.Electron-transport chain(3)第46页/共94页 All electron-transport pathways function in a similar manner,requiring a series of oxidation and re

49、duction reactions.The oxidation of a molecule involves the loss of electrons,and reduction involves the addition of electrons.Since electrons are conserved in chemical reactions,oxidation must be coupled with reduction(redox reactions).1.Electron-transport chain(4)第47页/共94页 The oxidation-reduction p

50、otential(redox potential)of a compound is a measure of its affinity for electrons.Redox potentials are measured relative to hydrogen;thus,a positive redox potential indicates that the compound has a greater affinity for electrons than has hydrogen and would accept electrons from hydrogen.A negative