Venturicidin Synthesis Lab Report

8265 Words34 Pages
2608T_ch19sm_S223-S237 02/22/2008 2:47 pm Page 223 pinnacle 111:WHQY028:Solutions Manual:Ch-19: Oxidative Phosphorylation and Photophosphorylation chapter 19 2H 1. Oxidation-Reduction Reactions The NADH dehydrogenase complex of the mitochondrial respiratory chain promotes the following series of oxidation-reduction reactions, in which Fe3 and Fe2 represent the iron in iron-sulfur centers, Q is ubiquinone, QH2 is ubiquinol, and E is the enzyme: (1) NADH 2 H E-FMN 88n NAD 2Fe 3 E-FMNH2 2Fe2 (2) E-FMNH2 (3) 2Fe 2H H 88n E-FMN 3 Q 88n 2Fe QH2 QH2 Sum: NADH Q 88n NAD For each of the three reactions catalyzed by the NADH dehydrogenase complex, identify (a) the electron donor, (b) the electron…show more content…
Effect of Venturicidin on Oxygen Evolution Venturicidin is a powerful inhibitor of the chloroplast ATP synthase, interacting with the CFo part of the enzyme and blocking proton passage through the CFoCF1 complex. How would venturicidin affect oxygen evolution in a suspension of well-illuminated chloroplasts? Would your answer change if the experiment were done in the presence of an uncoupling reagent such as 2,4-dinitrophenol (DNP)? Explain. Answer Oxygen evolution requires continuing passage of electrons through PSII. Electrons will continue to flow through PSII and the cytochrome b6 f complex until the energetic cost of pumping a proton across the thylakoid membrane exceeds the energy available from absorption of a photon. This point is soon reached when proton flow through CFoCF1 is blocked by venturicidin, and oxygen evolution ceases. Addition of an uncoupling agent provides a route for protons to move through the thylakoid membrane, dissipating the energy of the proton gradient. Electrons can now continue to move through PSII and the cytochrome b6 f complex, and oxygen is produced in the water-splitting reaction. 34. Bioenergetics of Photophosphorylation The steady-state concentrations of ATP, ADP, and Pi in isolated spinach chloroplasts under full illumination at pH 7.0 are 120.0, 6.0, and 700.0 mM, respectively. (a) What is the free-energy requirement for the synthesis of 1 mol of ATP under these conditions? (b) The energy for ATP synthesis is furnished by light-induced electron transfer in the chloroplasts. What is the minimum voltage drop necessary (during transfer of a pair of electrons) to synthesize ATP under these conditions? (You may need to refer to Eqn 13–7, p. 515.) Answer (a) G G RT ln [ATP] [ADP][Pi] (2.48 kJ/mol) ln 1.2 10 4 10 6) (7.0

More about Venturicidin Synthesis Lab Report

Open Document