FINAL_Answ.WI08

FINAL_Answ.WI08 - METABOLIC BIOCHEMISTRY Immo E. Scheffler...

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METABOLIC BIOCHEMISTRY BIBC102 Winter 2008 Immo E. Scheffler FINAL EXAM All answers are to be written into the Blue Book. Leave the first inside page blank for scoring and write a vertical column of numbers 1 - 16 There are 16 questions. Make sure that each answer is clearly identified with the question number at the top or left side of the page. Consider the statement on the back of the Blue Book; fill it out and sign it if you want to have your exam returned in the hallway outside of 3330 Bonner Hall. ********************************************************************************* QUESTION 1 [12 points] a) The famous biochemist O. Warburg looked in vain for an enzyme that could carry out the following reaction 2NADH + 2 H + + O 2 Î 2 H 2 O + 2NAD + What do we know now about how this oxidation of NADH is achieved in mitochondria? Explain with the help of a labeled diagram that also indicates where in mitochondria the necessary components are located.
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The diagram should show the three complexes (I, III, IV) in the inner mitochondrial membrane as well as the mobile carriers Q and cytochrome c at the appropriate locations. It should also be shown where NADH is oxidized and where oxygen is converted to water. (The proton pumping is not relevant for the answer here) QUESTION 2 [14 points] The following diagram is a schematic representation of the oxygen concentration in a chamber with mitochondria suspended in an appropriate phosphate buffer. Various reagents are added as indicated, with the result that oxygen consumption is either stimulated or arrested. a) The following is a list of substrates, inhibitors, etc., 1) rotenone 2) succinate 3) β -hydroxybutyrate (to make NADH) 4) ADP 5) cyanide you are to match them with the compounds A - E shown in the diagram: (oxygen concentration)
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A: addition of b-hydroxybutyrate ; no oxygen consumption in well-coupled mitochondria B: addition of ADP; complex V can now operate to make ATP and transport protons back into the matrix C: addition of rotenone, an inhibitor of complex I D: addition of succinate; it is oxidized by complex II E: addition of cyanide; it bind to complex IV instead of oxygen and stops respiration b) Instead of ADP one could have used the uncoupler dinitrophenol. Explain briefly. The uncoupler dinitrophenol provies an alternate pathway for protons to return to the matrix, and hence complex V activity is not required. QUESTION 3 [12 points] a) Explain what we mean by the P/O ratio. Why does it depend on whether succinate or NADH is being oxidized? [8] The P/O ratio is the ratio of ATP produced per oxygen atom converted to water. Whan NADH is used as a substrate a total of ten protons are pumped out of the matrix, providing energy for the synthesis of ~ 2.5 ATPs; when succinate is used as substrate, only six protons are pumped out, and hence only ~1.5 ATPs can be produced. With both substrates two electrons are sent to complex IV to produce water. b) Thermogenesis in brown adipose tissue is achieved by means of an
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This note was uploaded on 03/21/2009 for the course BIMM bimm 100 taught by Professor Dr.sato during the Fall '08 term at UCSD.

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FINAL_Answ.WI08 - METABOLIC BIOCHEMISTRY Immo E. Scheffler...

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