Análisis del transporte de electrones en bioquímica

2. 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) I1, I2 son inhibidores irreversibles de  y , respectivamente. 5) X1 y X2 son dadores de electrones exógenos.

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

4. Potencial electroquímico del protón n = 1 ; log ([H+]B/ [H+]A) =-pH H+=- F *  - 2.3 * 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 =  + 0.6 * pH

6. Energy transducing membranes. Chloroplast

7. CHEMIOSMOTIC THEORY ADP + Pi ATP Electron transport H+-ATPase

8. Flujo reverso de electrones ADP + Pi ATP

9. Uncoupled electron flow Uncoupler

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

12. H+-ATPase membrana

16. Energy of sunlight Useful chemical bond energy Light (via plants) complex carbon, glucose, amino acids Autotrophs: Phototrophs & chemotrophs Heterotrophs CO2, H2O (e.g. some bacteria, animals, humans) Chemical oxidations (via iron &sulfur bacteria) Need 9 amino acids & 15 vitamins from outside sources Organisms within the biosphere exchange molecules and energy 1st Law of Thermodynamics: In any process, the total energy of the universe remains constant.

17. H2O O2 NADP NADPH OBJETIVOS DE LA CLASE

18. 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 (CO2) and water (H2O). What is photosynthesis? Fig. 2.40 Molecular Biology of the Cell, 4th. Ed.

21. 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?

22. 6 O2 C6H12O6 6 CO2 6 H2O glucose oxygen carbon dioxide water ATP, NADPH Glucose synthesis  + + ATP, NADPH General reaction  O2 + CO2 H2O + (CH2O) Carbondioxide water Carbohydrate (e.g. sucrose or starch) oxygen Go’ = +686 kcal/mol Photosynthesis reactions overview • 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, CO2 to synthesize sugar & starch • Occurs in: prokaryotes: bacteria, blue green algae, in cytoplasmic membrane • eukaryotes: chloroplasts

23. Anatomy of a plant cell Fig. 14.34. Molecular Biology of the Cell, 4th. Ed.

24. 3 distinct membranes: outer, inner, thylakoid 3 separate internal compartments: intermembrane, stroma, thylakoid lumen An overview of the chloroplast grana Size = 5 m pp. 529

28. Chlorophyll pp. 530

30. 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 

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

32. Absorption and emission spectra of biphenyl

33. Chlorophyll. Absorption and emission spectra

34. Other pigments, antenna pigments, accessory pigments Reflects green light; absorbs rest Reflects yellowlight; absorbs rest Reflects blue light; absorbs rest

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

36. (Chl) (Chl)* D+ D Interconversión de la clorofila

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

38. LUZ A D P  P* P+ A- D+

39. Potenciales de óxido-reducción en el centro de reacción

41. proton gradient O2 The “Z” scheme of photosynthesis pp. 538

42. Photosystem II Thylakoid membrane • Transfers electrons from water to plastiquinone (thus oxidizing it to O2) • Generates proton (H+) gradient between thylakoid lumen and stroma pp. 534

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

46. Overview of electron flow through thylakoid membrane proteins The Cell: a molecular approach, fig. 10-22

47. Non-cyclic photophosphorylation when PSII is inhibited

48. Cyclic photophosphorylation

49. Pseudocyclic photophosphorylation

50. H2O O2 NADP NADPH OBJETIVOS DE LA CLASE