07exam6key - Name_KEY_ EID_ CH 339K Exam 6 6 Dec 2007 100...

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Name___________ KEY _____________________________ EID__________________________________________ 1 CH 339K Exam 6 6 Dec 2007 100 points total 1 . When pure reduced cytochrome c is added to carefully prepared coupled mitochondria along with ADP, P i , antimycin A, and oxygen, the cytochrome c becomes oxidized, and ATP is formed, with a P/O ratio approaching 1.0 (P/O ratio is the # of molecules of ATP synthesized per pair of electrons transferred from some reduced compound to oxygen). 5 pts. a . Indicate the probable route of electron flow in this system. Indicate all electron carriers involved. Cyt c Cu A heme a heme a 3 O 2 (i.e. complex IV) 5 pts. b . Why was antimycin A added? antimycin A is an inhibitor of complex III. It was added for two reasons: •to inhibit oxidation of endogenous substrates •to inhibit reverse electron flow (i.e. back up the respiratory chain) 5 pts. c . What does this experiment tell you about the location of coupling sites for oxidative phosphorylation? Because ATP is formed, with a P/O ratio of ~ 1.0, complex IV must be a coupling site (i.e. a site of proton pumping). 10 pts. d . Write a balanced equation for the overall reaction (including cyt c oxidation and ATP synthesis). Cyt c red + ½ O 2 + 2 H + Cyt c ox + H 2 O (X 2) ADP + P i ATP + H 2 O Net: 2Cyt c red + O 2 + ADP + P i + 4H + 2Cyt c ox + ATP + 2H 2 O [Cyt c (Fe 2+ )] [Cyt c (Fe 3+ )]
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Name___________ KEY _____________________________ EID__________________________________________ 2 10 pts. e . Calculate
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07exam6key - Name_KEY_ EID_ CH 339K Exam 6 6 Dec 2007 100...

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