photosynthesis植物光合作用教学课件

1、 植物生理学 Plant Physiology 第1页，共85页。Biochemistry & Molecular Biology of PlantsBob B. BuchananWilhelm GruissemRussell L. Jones植物学报 植物生理学植物生理学通信Plant Physiology Plant Cell Plant Science PlantaAnnual Review of Plant Physiology and Plant Molecular Biology第2页，共85页。 Part 1 Photosynthesis第3页，共85页。1.1 Overview

2、 of Photosynthesis1.1.1 Photosynthesis is a biological oxidation-reduction process. Reaction 1.1: Photosynthesis CO2+2H2A(CH2O)+2A+H2Oljtang:第4页，共85页。Reaction1.2: Oxygenic PhototsynthesisCO2+2H2O(CH2O)+O2+H20第5页，共85页。 Reaction1.3:Photosynthetic sulfur reductionCO2+2H2A(CH2O)+2S+H2O第6页，共85页。1.1.2 In

3、photosynthetic eukaryotes, photosynthesis takes place in the chloroplast, a specialized organelle 第7页，共85页。Chloroplast, a double-membrane system, consist of an out envelope and inner envelope.The internal membrane system , known as the thylakoids, contains granal thylakoids and stroma thylakoids.The

4、 thylakoid membranes are all interconnected and enclose an internalspace, the lumen.第8页，共85页。1.1.3 Photosynthesis requires the coordination of two phases: light reactions and carbon-linked reactions 第9页，共85页。Light reactions: produce O2, ATP, and NADPH.Carbon reduction cycle: reduce CO2 to carbohydra

5、te on consuming the ATP and NADPH.The conception that water oxidation and CO2 reduction were not obligately linked was first advanced in 1930s by Robert Hill.Reaction 1.4: Hill Reaction 2H2O+2AO2+2H2A第10页，共85页。1.2 Light Absorption and energy conversion. 1.2.1 Light is absorbed by pigment molecules.

6、PigmentPigment*第11页，共85页。第12页，共85页。 number of products formed photochemicallyEquation 1.2.1: Quantum Yield = - Number of quanta absorbed 第13页，共85页。1.2.2 Almost all photosynthetic organisms contain chlorophyll or a related pigment.第14页，共85页。Plants, Algae and Cyanobacteria: chlorophyll a or chlorophyl

7、l b.Anaerobic photosynthetic bacteria: bacteriochlorophyll a.Chlorophylls have a porphyrin ring structure that contains a central Mg atom coordinated to the four modified pyrrole rings. Chlorophyll molecules also contain a long hydrocarbon tail that makes the molecules hydrophobic. Various chlorophy

8、lls differ in their substituents around the ring structure.第15页，共85页。Biosynthesis of chlorophylls and hemes.第16页，共85页。 1.2.3 Carotenoids and xanthophylls participate in light absorption and photoprotection. 第17页，共85页。第18页，共85页。1.2.4 Absorption spectra of chlorophylls and other photosynthetic pigment

9、s 第19页，共85页。第20页，共85页。1.2.5 Red algae and Cyanobacteria contain accessory pigments that absorb green light.第21页，共85页。第22页，共85页。1.3 The reaction center complex .1.3.1 Reaction centers are integral membrane protein complexes involved in conversion of light energy into chemical products.1.3.2 Reaction

10、centers contain both special chlorophyll and electron acceptor molecules involved in energy conversion. 1.3.3 The structure of a reaction center from a photosynthetic bacterium has been determined. 第23页，共85页。第24页，共85页。1.3.4 The kinetics of primary charge separation events are understood in great det

11、ail. 第25页，共85页。第26页，共85页。1.3.5 Oxygenic photosynthetic organisms contain two photochemical reaction centers, PSI and PSII1.3.5.1 Structure model of the PSII reaction center.第27页，共85页。第28页，共85页。1.3.5.2 Structure model of the PSI reaction center.第29页，共85页。1.4 The Photosystem 1.4.1 A photosystem contai

12、ns a photochemical reaction center and multiple antennae ( auxiliary light-harvesting pigment-protein complexes).1.4.2 Most oxygenic photosynthetic organisms contain chlorophyll a/b proteins as their principal antennae. 第30页，共85页。Table 1.4.2 Properties of light-harvesting chlorophyll protein complex

13、esComplex Chl a/b ratio Gene Mol. Mass(kDa)Light-harvesting complexes (LHC) associated with PSLHC-a 2.0-3.1 lhca3 20.5(LHC-680) lhca2 18LHC-b 2.2-4.4 lhca1 20(LHC-730) lhca4 20Light-harvesting complexes associated with PSLHC-a (CP29) 4.0 lhcb4 29LHC-b 1.35 lhcb1 27-28LHC-c (CP26) 2.9 lhcb5 26.5LHC-d

14、 (CP24) 1.51 lhcb6 24第31页，共85页。1.4.2 The organization of pigments in PS and PS.第32页，共85页。1.4.3 The light-harvesting antennae of organism that contain phycobilins第33页，共85页。Reaction 1.4.3 Energy transfer in a phycobilisomePhycoerythin(PC) Phycocyanin(PE) Allophycocyanin(APC) Chl a第34页，共85页。1.5 Organiz

15、ation of thylakoid membrane1.5.1 Protein complexes of the thylakoid membrane exhibit lateral heterogeneity.第35页，共85页。1.5.2 Phosphorylation of LHC- may influence the distribution of energy between PS and PS第36页，共85页。第37页，共85页。1.6 Electron transport pathways in chloroplast membranes1.6.1 The chloropla

16、st noncyclic electron transport chain produces O2,NADPH, and ATP and involves the cooperation of PS and PS第38页，共85页。第39页，共85页。1.6.2 Photosystem stoichiometry variesby species and is influenced by light environment.Table 1.6.2 Stoichiometry of the photosystems in different oxygen-evolving systems and

17、 in response to changes in light quality _ System PS/PSratioCyanobacteria 0.4Red algae 0.4Green algae 1.4Tobacco mutant su/su 2.7Pea chloroplasts From plants grown in PS light (550-660nm) 1.2 From plants grown in sunlight 1.8 From plants grown in PS light(660nm) 2.3 第40页，共85页。1.6.3 PS functions as a

18、 light-dependent water-plastoquinone oxidoreductase.第41页，共85页。第42页，共85页。 Table 1.6.3 Protein subunits of the PS core complexeHydrophobic subunitsProtein Gene Location of gene FunctionD1 psbA Chloroplast Reaction center proteinD2 psbB Chloroplast Reaction center proteinCP47 psbC Chloroplast Antenna b

19、indingCP43 psbD Chloroplast Antenna bindingCytb559 subunit psbE Chloroplast Unknown subunit psbF Chloroplast UnknownPsbH-PsbN psbH-psbN Chloroplast Unknown22kDa psbS Nucleus PhotoprotectionHydrophilic subunits33kDa psbO Nucleus Oxygen evolution23kDa psbP Nucleus Oxygen evolution17kDa psbQ Nucleus Ox

20、ygen evolution10kDa psbR Nucleus Unknown第43页，共85页。1.6.4 Oxidation of water produces O2 and releases electrons required by PSReaction 1.6.4 : Oxidation of water 2H2OO2+4H+4e-第44页，共85页。The pattern of oxygen evolution is given in response to a series of short flashes of light第45页，共85页。The oxygen evolut

21、ion apparatus is considered to exist in five different oxidation states (So through S4)第46页，共85页。Structure of the manganese cluster第47页，共85页。1.6.5 The cytochrome b6f complex transfers electrons from reduced plastoquinone to oxidized plastocyanin第48页，共85页。Proton translocation via cytochrome b6f is th

22、ought to involve a Q-cycleReaction1.6.5: The Q-cycle in the chloroplastPQH2+2PCox+2H+stroma PQ +2PCred+4H+lumen第49页，共85页。第50页，共85页。第51页，共85页。1.6.6 Pastocyanin, a soluble protein, links cytochrome b6f and PS第52页，共85页。1.6.7 PS function as a light-dependent plastocyanin-ferredoxin oxidoreductase第53页，共8

23、5页。Electrons from PS are transferred to NADP+ in the stroma in a reaction requiring ferredoxin and ferredoxin-NADP+ reductase第54页，共85页。1.6.8 Specific inhibitors and artificial electron acceptors have been used to study the chloroplast electron transport chainD1第55页，共85页。第56页，共85页。1.6.9 Chloroplasts

24、also contain a cyclic electron transport chain第57页，共85页。第58页，共85页。1.7 ATP synthesis in chloroplasts1.7.1 Electron transport and ATP synthesis are coupled in vivo.1.7.2 Chloroplasts synthesize ATP by a chemiosmotic mechanism driven by a proton gradient.In the 1960s, Peter Mitchell proposed the chemio

25、smotic model to explain ATP synthesis in chloroplasts as well as in mitochondria. The experimental verification of this hypothesis in the 1960s and 1970s resulted in Mitchells receiving the 1978 Nobel Prize in chemistry.第59页，共85页。第60页，共85页。1.7.3 Experimental manipulation of lumenal and stromal pH ca

26、n promote light-independent ADP phosphorylation in chloroplasts.Acid-base PhosphorylationChloroplasts were first incubated at about pH4, allowing them to establish this pH internally. The chloroplast suspension was then rapidly adjusted to pH8, establishing an artificial pH gradient across the membr

27、ane. This artificial pH gradient promoted ATP synthesis until it was discharged and the pH difference was insufficient to drive ADP phosphorylation.Acid-base ATP synthesis required no light and was insensitive to electron transport inhibitor, such as DCMU, indicating that a pH gradient alone was suf

28、ficient to drive ATP synthesis.第61页，共85页。1.7.4 The most widely accepted mechanism of ATP synthesis is the so-call binding change mechanism proposed originally by Paul Boyer ( a co-recipient of 1997 Nobel Prize in chemistry)第62页，共85页。1.8 Carbon reactions in C3 plantsMost plants produce a three-carbon

29、 compound, 3-phosphoglycerate (3-PGA), as the first stable product in the multistep conversion of CO2 into carbohydrate. This functionally defined group, which includes most crop plants, is referred to as C3 plants.第63页，共85页。The Calvin cycle is divided into three phases: carboxylation, reduction, an

30、d regeneration.第64页，共85页。第65页，共85页。1.9 C4 plants contain two distinct CO2-fixing enzymes and have specialized foliar anatomy第66页，共85页。1.9.1 The C4 pathway increases the concentration of CO2 in bundle sheath cell.第67页，共85页。The bundle sheath chloroplast lacks stacked thylakoids and contains little PS第

31、68页，共85页。1.9.2 Variations in C4 photosynthesisThree variations of C4 photosynthesis are known, differing in the C4 acids transported between mesophyll and bundle sheath cells as well as in the mechanism of decarboxylation in the bundle sheath cell.The variations are named on the basis of the decarbo

32、xylase enzymes in the bundle sheath cells.第69页，共85页。第70页，共85页。1.9.4 Ontogeny of C4 patternsIn the development of most C4 leaves, the expression of C4 genes does not occur until Kranz anatomy has been established.The appearance of C4 activities has been compared in leaves 1-5 of maize seedlings: the

33、first leaf initiated (leaf 1) was more C3 in charater, while the last measured (leaf 5) was fully C4.Some studies showed that callus cultures derived from C4 plants do not exhibit a functioning C4 pathway until cells organize into shoots and vascular development is under way.Physiological measuremen

34、ts suggest that the observed patterns of gene expression reflect the function of the C4 carbon fixation pathway near veins and the C3 pathway at more distant locations第71页，共85页。1.9.3 C3-C4 intermediate plants and evolution of photosynthetic systemSpecies with anatomical and physiological characteris

35、tics intermediate between C3 and C4 exist in many plant families. The characteristics of these intermediate species represent evolutionary steps between C3 and C4 plants, although all point out that C3-C4 intermediate physiology need not result from partial function of the C4 system.Certain genera (

36、 Flaveria) contain C3, C4, and C3-C4 intermediate species and therefore provide the opportunity to study the concordance of changes in anatomy with physiology among related species.Taxonomical and phylogenetical studies suggest that CAM and C4 plants were derived from C3 plants and the transitions o

37、ccurred many times in diverse taxa during the course of evolution. A drastic decline in atmospheric CO2 level during the late Cretaceous period (65-85 million years ago), a time of major expansion of the angiosperms , has been proposed to account for the increase of C4 plants.第72页，共85页。1.9.5 The cha

38、nge of photosynthetic pathwayC4 carbon fixation pathway has been found in some C3 plants.C3 pathway could become a dominant pathway in C4 plants during the process of senescence.Many aquatic and amphibious C4 species exhibit a remarkable developmental plasticity that permits modulation of C3 vs C4 f

39、ixation along with variations in leaf anatomy depending on habitat.( Eleocharis ) The submersed monocot Hydrilla verticillata typically exhibits C3 character, but exposure to low ( CO2) induces a C4 system in which the C4 and Calvin cycle co-exist in the same cell.第73页，共85页。1.9.6 Molecular engineeri

40、ng of C4 enzymes in C3 plantsPEPCEffects of overexpression of PEPC on photosynthesis are controversial. At temperatures optimal for plant growth, practically no difference in the rate of CO2 assimilation and CO2 compensation point was observed in transgenic tobacco expressing the maize PEPC gene.In

41、transgenic rice plants expressing the maize PEPC gene, the rate of CO2 fixation was not altered significantly, but O2 inhibition of net CO2 assimilation was mitigated with increasing activity of PEPC.第74页，共85页。PPDKTransgenic Arabidopsis, potato, rice expressing the maize C4-specific PPDK gene, and t

42、ransgenic tobacco expressing a PPDk gene from the CAM plant showed no change s in photosynthetic characteristics.Future perspectivesExperiments with transgenic plants have reinforced the fact that the C4 mechanism is a finely tuned metabolic “ machine” where both a high degree of precision in gene expression and structural morphology work together to concentrate CO2 efficiently at the site of Rubisco.第75页，共85页。1.10 CAM metabolism involves t