《植物细胞解剖学》课程教学资源（PPT）04

CYTOSOL PLASTID Storage, phloem transport==Sucrose I Starch Pentose Glycolysis Pentose phosphate phosphate pathway Hexose-P Hexose-Pl pathway Pentose-P Pentose-P Triose-P Triose-P CO?NADPH CO2 NADPH Photosynthesis Storage Organic acids ATP NADH空ATP MITOCHONDRION NADH Citric acid FADH2 Oxidative phosphorylation cycle breakdown Figure 4-1

Figure 4-1

Initial phase of glycolysis substrates from different moln me ere channeled into triose phosphate, For stare nolecules of triose phosphate CYTosoL Sucrose process requires an input of up to 4 ATP PLASTID Invertase Sucrose synthase Glycolysis Glucose Fructose UDP-Glucose phosphorylasE Starch PD H2o.Amylase ATP CATP PP: UDP-Glucase pyrophosphorylase 1-P Glucose Hexokinase UTP CADPD ADPD cosewl-E Phospho ATP J Phosphoglucomutase p Glucose kinase Glucose6-P a Fructose.P e GIucose6-P Glucose.t Hexose phosphates Hexes AMYLOPLASTS ate phosphato isomerase fomor .ATP hosphofructokir opende phosphofructokinase PCADP Fructose-1 6-bisphosphate Aldolase CHLOROPLASTS Trios Glyceraldehyde Dihydroxyacetone Triose phosphates 3-phosphate ose phosphate phosphate phosphates NAD+ NADH+ Eneroy-conserving phase of glycoysis 3-phosphate dehydrogenase NAD. prespurcet s nApe tv ocerrdetvd 1.3-Bisphosphogtycerate Phosphoglycerate kinase Phosphen alterno sactions catalyzed by 式ATP PhosphoenoypN ive end produevato be converted to 3-Phosphoglycerate an be reoxidized during fermentation Phosphoglycerate mutase dehydrogenase 2-Phosphoglycorate HO Enolase HcOa Phosphoenolpyruvate PEP carboxylase oxaloacetate Pyruvate kinase NADH Malate AT NAD+ Pyruvate [ Malate NADH Lactate INAD+ dehydrogenase Pyruvate Lactate carboxylase MITOCHONDRION Figure 4-2 Acetaldehyd NADH Alcohol dehydrogenase 扩tien Ethanol reactions

Figure 4-2

Intermembrane space- Outer membrane Inner membrane CADP ATP Matrix Cristae FIGURE 1.15(A)Diagrammatic representation of a mito- chondron, including the location of the H*-ATPases involved in ATP synthesis on the inner membrane. Figure 4-3 (B)An electron micrograph of mitochondria from a leaf cell of Bermuda grass, Cynodon dactylon(26,000x)(Photo by s. E. Frederick, courtesy of E. H. Newcomb.)

Figure 4-3

Malic enzyme decarboxylates malate to ruvate pyruvate and enables H plant mitochondria to oxidize malate NAD. vale NADH cO? CH, NADH Citrate Malic dehydrogenase -CH2- enzyme AD NAD' Oxaloacetate Citrate Aconitase Malate Fumarase Citric Isocitrate -2-2 nel Fumarate cycle NADT Succinate dehydrogenase Isocitrate dehydrogenase NADH Succinate 2.Oxoglutarate eCO - ATP succinyl-CoA Succinyl-CoA synthetase (ADP One molecule of ATp is 2-oxoglutarate dehydrogenase synthesized by a substrate- level phosphorylation CO, INADH during the reaction catalyzed by succinyl-CoA FIGURE 11.6 Reactions and enzymes of the plant citric acid cycle, Pyruvate is Figure 4-4 completely oxidized to three molecules of CO,. The electrons released during these oxidations are used to reduce four molecules of NAD' to NADH and one molecule of FAD to FADH

Figure 4-4

NADPH is generated in the first The ribulose-s-phosphato is two reactions of th converted to tho acolyte where qlucose-s phosphate intermediates fructose bese reactions are esse品t hosphate d olyceraldehycte-3t- irreversible Poegtap ie interconversion TH。s H,O-(P) reactions are freely eversible Ribulose-5-phosphate Pentose phosphate Homare Glucose-6-phosphate Glucose-6- NADPY HIsOft - NADPH HoR HcON Hc《 CH,O-(P) CH,(P) HoArd Ribose-5-phosphate Xylulose-5-phosphate Transketolase CH,OH G-Phosphoglucorete co NADP *NADPH CHO-P) dehydroge CHOH lvceraldehydc HCOH RiCOH HCOH HCOH pilose 7-phosphate CH,O-(P) Ribulose-S-phosphate Transaldolase CHOI cHIe cO》4 HocH Hexose phosphate Isomerase CH2O-E throne- hosphate CHo-P Transketolase Fructose-6-phosphate HoI CH,O-(P) Figure 4-5

Figure 4-5

INTERMEMBRANE SPACE Extemal (rotenone-insensitive) The ubiquinone(UQ) pool diffuses NAD(P)H dehydrogenases can accept freely within the innermembrane and Cytochrome c is a peripheral electrons directly from NAD(P)H protein that transfers electron serves to transfer electrons from the n from complex ill to complex IV ner produced in the cytosol membrane dehydrogenases to either complex lll or the alternative oxidase NAD NADP NADH NADPH 2 3 yt c AOX Succinate HO NADH NADH NADPH Fumarate H2o Complex l Complex IV NADT NAD+ NADP. Complex ll Cytochrome bG, Cytochrome Succinate complex Complex I Rotenone-insensitive dehydrogenase ATP ( ADP)+(P) of the membra An alternative oxidase ( AOX) accepts electrons directly Complex V from ubiquinone ATP synthase MATR Figure 4-6 FIGURE 11.8 Organization of the electron transport chain enzymes pumps protons. Specific inhibitors, rotenone for and ATPsynthesis in the inner membrane of plant mito- complex I, antimycin for complex Ill, cyanide for complex chondria. In addition to the five standard protein com- IV, and salicylhydroxamic acid(SHAM)for the alternative plexes found in nearly all other mitochondria, the electron oxidase, are important tools to investigate the electron transport chain of plant mitochondria contains five addi transport chain of plant mitochondria. tional enzymes marked in green. None of these additional

Figure 4-6

:NADH NAD+=NADPH(NADP Intermembrane space Inner Complex Ill membrane Complex I or pool Alternati xida Matrix NADH (NADT NADPH(NADP Figure 14.25 drial membrane. In addition to Complex I, plant mitochondria possess simpler on Rotenone-insensitive NADH and NADPH dehydrogenases of the inner mitochon membrane.These do not pump protons and are insensitive to Complex I inhi.> (single polypeptide) dehydrogenases on both surfaces of the mitochondrial inn bitors such as rotenone. Four dehydrogenases have been described, although not all of these may occur in all plant tissues. The two external dehydrogenases are thought to oxidize cytosolic NAD(P)H and feed electrons into the UQ pool. The two enzymes on the inner surface provide additional routes for oxidation of the NADH and NADPH formed in the matrix. The proteins involved in these pro- cesses have not yet been firmly identified Figure 4-6-0

Figure 4-6-0

Intermembl sp IN-2 Fe/S uO Figure 4-6-1 UQH Figure 14 19 osed structure and membrane topography of mi Mat trix 2 tochondrial complex I (NADH: UQ oxidoreductase) n The complex acts as an NADH-ubiquinone oxidore- ductase, transferring electrons from matrix NADH - to ubiquinone. This transfer involves FMN, fo NADH多 iron-sulfur centers(Nl-N4)and an internal quinone (UQ ) The H/2e ratio is thought to be four two H taken up at the internal quinone site IN-1, N-3, N-4 other two translocated by a poorly defined mecha Fe/S nism(dotted line). The complex is readily bro FMN into two smaller complexes, one of which (blue)is very hydrophobic and contains all of the subunits encoded in the mitochondrion. The other arm of the (600 kDa) lex (purple) protrudes into the matrix and is composed of nucleus-encoded subunits

Figure 4-6-1

Figure 4-6-2 UQ Figure 14. 21 UGH subunits that make up succinate dehydrogenase are S1/S2 FAD low), while three iron-sulfur clusters(S-1, S-2, and Succinate Fumarate

Figure 4-6-2

(B) Intermembrane space Cytc ytc ℃ Fe-SUOHzJUC Fe-S Center P) e UO+(+ nter Figure 14.22 LUOH (A)Diagram illustrating proposed structure and membrane topography of mitochondrial Complex Ill (ubiquinone: cytochrome-c oxidore- ductase, also known as cytochrome bG,).The complex is a dimer, with each monomer con taining multiple subunits, Ubiquinol (UQH-) is oxidized at Center P, while ubiquinone (UQ) is reduced at Center N. The two electrons from UQH2 take divergent paths, one being trans- ferred to mobile cytochrome c via a Rieske iron-sulfur center and cytochrome cy, the other reaching Center N via two b-type cytochromes The inhibitory sites of antimycin and myxo- Complex Ill thiazol are at Centers N and P, respectively Matrix Figure 4-6-3 (500kDa) (B)Crystal structure of a dimeric mammalian cytochrome bc, complex

Figure 4-6-3