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Análisis del transporte de electrones en bioquímica 1) Los componentes A y D son el dador y el aceptor de electrones exógenos, respectivamente. 2) Los.

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Presentation on theme: "Análisis del transporte de electrones en bioquímica 1) Los componentes A y D son el dador y el aceptor de electrones exógenos, respectivamente. 2) Los."— Presentation transcript:

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3 Análisis del transporte de electrones en bioquímica 1) Los componentes A y D son el dador y el aceptor de electrones exógenos, respectivamente. 2) Los componentes B y C de la cadena de transporte de electrones se encuentran en baja concentración en la membrana. 3) ,  y  catalizan la transferencia de electrones 4) I 1, I 2 son inhibidores irreversibles de  y , respectivamente. 5) X 1 y X 2 son dadores de electrones exógenos.

4 Diferencia de potencial electroquímico de un ion Para transferir un mol de ion X n+ a través de una membrana cuando : - [X n+ ] B  [X n+ ] A, en ausencia de un campo eléctrico.  G = 2.3 * R * T * log([X n+ ] B / [X n+ ] A ) - [X n+ ] B = [X n+ ] A, en presencia de un campo eléctrico.  G = - n * F *  donde F: constante de Faraday; n: carga del ion;  : potencial eléctrico - [X n+ ] B  [X n+ ] A, en presencia de un campo eléctrico.  G = - n * F *  * R * T * log([X n+ ] B / [X n+ ] A )

5 Potencial electroquímico del protón n = 1; log ([H + ] B / [H + ] A ) = -  pH  H + = - F *  * R * T *  pH Multiplicando por [1 / ( - F)]  H + / ( - F) =  - [2.3 * R * T * ( - F)] *  pH A 25 oC, [2.3 * R * T * F] = 0.6  H + / ( - F) =  p (potencial protón motriz)  p =  *  pH

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7 Energy transducing membranes. Chloroplast

8 ATP ADP + Pi CHEMIOSMOTIC THEORY Electron transport H + -ATPase

9 ADP + Pi ATP Flujo reverso de electrones

10 Uncoupler Uncoupled electron flow

11 ATP-synthase A H + gradient in chloroplasts makes ATP via ATP-synthase. pp. 540 How is ATP made? Photophosphorylation

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13 membrana H + - ATPase

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17 Organisms within the biosphere exchange molecules and energy 1 st Law of Thermodynamics: In any process, the total energy of the universe remains constant. Energy of sunlight Useful chemical bond energy humans (e.g. some bacteria, animals, humans) complex carbon, glucose, amino acids CO 2, H 2 O Autotrophs : Phototrophs & chemotrophs Heterotrophs Chemical oxidations (via iron & sulfur bacteria) Light (via plants) Need 9 amino acids & 15 vitamins from outside sources

18 NADP NADPH H 2 O O 2 OBJETIVOS DE LA CLASE

19 What is photosynthesis? The process by which plants, algae, and some bacteria use solar energy to drive the synthesis of organic molecules (e.g. sugars, starch, etc.) from carbon dioxide (CO 2 ) and water (H 2 O). Fig Molecular Biology of the Cell, 4th. Ed.

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22 1.How are plants able to convert light energy into energy that can be utilized by both themselves and heterotrophs? What other organisms can do this?

23 Photosynthesis involves two parts: 1. Light reactions (mediated by chlorophylls) use light to generate ATP, NADPH 2. Carbon reactions (also called, “Benson-Calvin cycle”) use ATP, NADPH, CO 2 to synthesize sugar & starch Occurs in: prokaryotes: bacteria, blue green algae, in cytoplasmic membrane eukaryotes: chloroplasts Photosynthesis reactions overview glucose C 6 H 12 O 6 ATP, NADPH  G o’ = +686 kcal/mol +6 CO 2 carbon dioxide 6 H 2 O water 6 O 2 oxygen + Glucose synthesis  Carbohydrate (e.g. sucrose or starch) (CH 2 O)+CO 2 Carbon dioxide H2OH2O water O2O2 oxygen + ATP, NADPH General reaction 

24 Anatomy of a plant cell Fig Molecular Biology of the Cell, 4th. Ed.

25 grana pp. 529 chloroplast An overview of the chloroplast 3 distinct membranes: outer, inner, thylakoid 3 separate internal compartments: intermembrane, stroma, thylakoid lumen Size = 5  m

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29 pp. 530 Chlorophyll

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31 Absorption process Transition of an electron from the ground state to an excited state provided: A) The energy gap [ground state  excited state] matches the wavelength of light [E = h. c. -1 ] 2) the translation charge across a chromophore generates a transition electric dipole moment (  ) 3)  dictates the potential extent of absorption quantified as the extintion coefficient 

32  F = photons emitted / photons absorbed JCE 76: 1555 (1999) Deactivation processes of the excited states

33 Absorption and emission spectra of biphenyl

34 Chlorophyll. Absorption and emission spectra

35 Other pigments, antenna pigments, accessory pigments Reflects blue light; absorbs rest yellow Reflects yellow light; absorbs rest green Reflects green light; absorbs rest

36 Absorbance spectra of other pigments  The combined absorption of all the chlorophylls cover the entire spectrum of visible light.

37 (Chl)(Chl) * D+D+ D Interconversión de la clorofila

38 Antenna pigments pp. 543 Structure of a photocenter Electron transfer from accessory (i.e. antennae) pigments to reaction center. LIGHT

39 LUZ P  P * P+P+ A A-A- D D+D+

40 Potenciales de óxido-reducción en el centro de reacción

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42 O2O2 proton gradient pp. 538 The “Z” scheme of photosynthesis

43 pp. 534 Photosystem II Thylakoid membrane  Transfers electrons from water to plastiquinone (thus oxidizing it to O 2 )  Generates proton (H + ) gradient between thylakoid lumen and stroma

44 pp. 537 Photosystem I Thylakoid membrane Generates reduced ferredoxin (Fd) PSI reduces NADP + to NADPH (Fd-NADP-reductase).

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47 Overview of electron flow through thylakoid membrane proteins The Cell: a molecular approach, fig

48 Non-cyclic photophosphorylation when PSII is inhibited

49 Cyclic photophosphorylation

50 Pseudocyclic photophosphorylation

51 NADP NADPH H 2 O O 2 OBJETIVOS DE LA CLASE

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53 Autotrophy

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55 .....

56 substratesproducts The ferredoxin- thioredoxin system

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58 RUBISCO

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60 Residencia del DNA que codifica para Rubisco OrganismoLSUSSU Algas verdes, plantas, Euglena cloropl.Núcleo Algas rojas cloropl.cloropl. Algas marrones cloropl.cloropl. Dinoflagelados Núcleo X L8S8L8S8 L2L2

61 RUBISCO

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63 En la presentacion dice que es una planta C4. Documentos lindos \facultad \para usar \photos\photosynth \general1 (carpeta) \ C4leaf

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65 Plant C3 C4 CAM gH 2 O/g DM T opt ( o C) ca. 35 Ton.DM/(Ha.yr) low & variable Plant performance

66 mesophyll C4 photosynthesis. CO 2 fixation

67 (bundle sheath) mesophyll C4 photosynthesis. CO 2 assimilation

68 CO ATP + 2 H 2 O CO ADP + 2 P i bundle sheath mesophyll Cost of concentrating CO 2 within the bundle sheath cell

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70 DAYNIGHT Crassulacean acid metabolism

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72 BIBLIOGRAFIA PLANT PHYSIOLOGY, 3rd. Ed., L.Taiz & E.Zieger Eds., Ch.7. Photosynthesis: the light reactions Ch.8. Photosynthesis: carbon reactions Sinauer Associates, Sunderland, MA. (2002) BIOLOGIA CELULAR Y MOLECULAR, 4th. Ed., H.Lodish et al. Eds., Ch.16. Energética celular: glicólisis, oxidación aeróbica, y fotosíntesis. Editorial Panamericana, Buenos Aires. (2000) BIOENERGETICS 2, D.G.Nicholls & S.J.Ferguson. Academic Press, London. (1992)


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