Final.SU07Answ scheffler

Final.SU07Answ scheffler - METABOLIC BIOCHEMISTRY Immo E...

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METABOLIC BIOCHEMISTRY Winter 2001 Immo E. Scheffler FINAL EXAM ANSWERS All answers are to be written into the Blue Book. Leave the first inside page blank for scoring. There are 17 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 3234 Bonner Hall. ********************************************************************************* QUESTION 1 [14 points] a) NADH is oxidized via the electron transport chain with the eventual formation of water from oxygen. What are the complexes and mobile carriers involved in this oxidation, and what is the sequence of electron flow? (A simple schematic diagram with labels is required). A drawing should show the membrane, the four complexes I, II, III, and IV, the correct positioning of co-enzyme Q in the membrane between I (or II) and III, and the correct position of cytochrome c on the outer side of the inner membrane. CoQ and Cytc should be identified as the mobile carriers Arrows or some indication of electron flow from NADH to oxygen should be given. 10 points b) Describe two major structures that can make a protein a conductor of electrons a heme group associated with a polypeptide or a non-heme iron sulfur center ([Fe-S] 4 points
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QUESTION 2 [12 points] The following diagram is a schematic representation of the oxygen concentration in a chamber containing mitochondria; various substrates, inhibitors or uncouplers are added as indicated, with the result that oxygen consumption is either stimulated or arrested. For each of the substances added, rationalize the observed result. A. malate/glutamate does not stimulate oxygen consumption in coupled mitochondria; when ADP is added (Pi being present in the buffer), the complex V can operate and allow protons to enter the matrix; oxygen consumption (respiration) takes place; rotenone is an inhibitor of complex I and hence its presence will stop oxidation of NADH (derived from malate/glutamate); succinate feeds electrons into complex II and hence by-passes the block by rotenone: respiration resumes; malonate is a competitive inhibitor of complex II (succinate dehydrogenase). 6 points B. Again, the addition of malate/glutamate to coupled mitochondria does not lead to oxygen consumption, because of the inhibition (by mass action) of the electron transport by the built-up proton gradient. Dinitrophenol is an uncoupler, i.e. allows protons to return to the matrix without going through complex V; respiration will take place; respiration is finally stopped by cyanide, an inhibitor of complex IV (at the site where oxygen would bind). 6 points
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QUESTION 3 [10 points] a) Explain briefly how one can explain the experimental observation that the P/O ratio (ATP made per 1/2 O 2 consumed) is not an integer (i.e. 3.0 or 2.0) Electron transport (governing oxygen consumption) and ATP synthesis take place in physically distinct
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This note was uploaded on 09/11/2009 for the course BIBC BIBC 102 taught by Professor Price during the Spring '08 term at UCSD.

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Final.SU07Answ scheffler - METABOLIC BIOCHEMISTRY Immo E...

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