ps2_sol - Systems Microbiology 1.084J/20.106J PROBLEM SET...

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Systems Microbiology 1.084J/20.106J PROBLEM SET #2 – Due Monday Oct. 2 nd Problem 2.1 a. What does proton motive force mean, and why is it important in biology? (Ch.5 Review Question [RQ] 14) The porton motive force is an “energized” state of a membrane created by the expulsion of protons to the exterior face of the membrane creating a “charge separation” similar to a battery. The dissipation of this charge gradient through a membrane-bound ATPase complex provides energy for ATP synthesis. b. How is rotational energy in the ATPase used to produce ATP? (Ch.5 RQ 15) Rotational energy in ATPase is used to produce ATP via proton motive forse coupled to conformational changes in subunits of ATPase holoenzyme. Movement of protons through the F o subunit drives rotation of the c proteins generating torque. Conformational changes in the β -subuint transfers this potential energy to the F 1 subunit. Problem 2.2 a. What are the differences in electron donor and carbon source used by Esherichia coli and Acidithiobacillus thioparus (a sulfur chemolithotroph)? (Ch.5 RQ 19) Electron transport chains with oxygen as the final electron acceptor are utilized by both organisms. E. coli oxidizes organic compounds to produce energy, whereas A. thioparus oxidizes inorganic sulfur to use it as an electron donor. b. The following is a series of coupled electron donors and electron acceptors. Using Figure 5.9, order this series from most energy-yielding to least energy-yielding. (Ch.5 RQ 9) H 2 /Fe 3+ H 2 S/O 2 CH 3 OH/NO 3- H 2 /O 2 Fe 2+ /O 2 NO 2- /Fe 3+ H 2 S/NO 3- H 2 /O 2 , H 2 /Fe 3+ , H 2 S/O 2 , CH 3 OH/NO 3- , H 2 S/NO 3- , NO 2- /Fe 3+ , Fe 2+ /O 2 c. Explain the circumstances under which the same substance can be either an electron donor or an electron acceptor. The coupler pairing determines acceptor versus donor. The substance with a more positive E o ’ is the e - donor and the more negative E o ’ is the e - acceptor. Thus, depending on the available copule for reduction or oxidation, and the relative concentrations of each species (both e - donor and acceptor) a substance will act as an e - acceptor or donor. d. Consider the following reaction: NADH + fumarate succinate + NAD + + H + a. Using Table 1 calculate the Δ E 0 ' of the reaction. What is the Δ G 0 '? Does this reaction produce or consume energy? Δ
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This note was uploaded on 11/11/2011 for the course BIO 20.010j taught by Professor Lindagriffith during the Spring '06 term at MIT.

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ps2_sol - Systems Microbiology 1.084J/20.106J PROBLEM SET...

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