FINAL SU06.2ANSW_2

FINAL SU06.2ANSW_2 - 9/2/2006 11:08 AM METABOLIC...

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9/2/2006 11:08 AM METABOLIC BIOCHEMISTRY Summer 2006 Immo E. Scheffler FINAL EXAM All answers are to be written into the Blue Book. Leave the first inside page blank for scoring. There are 12 questions. Make sure that each answer is clearly identified with the question number at the top or left side of the page. QUESTION 1 (18 points) 1
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9/2/2006 11:08 AM There are six structural formulae for co-factors encountered during the course. Identify each of them by name (or abbreviated name), and give the name for the generic reactions in which they participate (oxidation reduction, decarboxylation, carboxylation, fatty acid oxidation) (6x3 points). A: biotin; used in carboxylation reactions B: coenzyme A; used in fatty acid degradation and synthesis, pyruvate dehydrogenase C: lipoic acid: used in pyruvate dehydrogenase D: thiamine pyrophosphate: used in decarboxylation reactions E: ubiquinone: used as mobile carrier in electron transport F: Flavin-adenine dinucleotide: used in various redox reactions 3 points each QUESTION 2 (5 points) Radioactive pyruvate with [ 14 C] in the 2 position (the keto-group) is given to isolated mitochondria. The Krebs cycle is inhibited by malonate, a competitive inhibitor of succinate dehydrogenase (complex II). Radioactive intermediates from the early reactions of the Krebs cycle are isolated and analyzed. Give a structural formula of α -ketoglutarate and indicate the carbon atom that would be the radioactive carbon derived from the radioactive pyruvate. 2
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9/2/2006 11:08 AM In the structure on the right carbon #5 is derived from the ketogroup of pyruvate; it becomes the carboxyl group after the pyruvate dehydrogenase reaction QUESTION 3 (10 points) In the Krebs cycle isocitrate is converted to α -ketoglutarate. In the glyoxylate cycle in glyoxysomes of germinating seeds the isocitrate is involved in a different reaction. What is the reaction? (Structural formulae are required). What is the specific function of the glyoxylate cycle? The reaction is catalyzed by isocitrate lyase; isocitrate is split to form succinate and glyoxylate. The glyoxylate cycle in germinating seeds permits the conversion of fatty acids to carbohydrates via the formation of acetyl CoA. In the glyoxylate cycle no CO 2 is generated, hence no carbons are lost. 7 points for the correct equation and structural formula; 3 points for a correct explanation for the function of the cycle. 3
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9/2/2006 11:08 AM QUESTION 4 ( 24 points ) a) In P. Mitchell’s “chemiosmotic hypothesis” the energy released from the oxidation of NADH via the electron transport chain is used to drive ATP synthesis (in tightly coupled mitochondria). Illustrate the hypothesis with a schematic diagram and describe in words the main ideas of this hypothesis. (12 points) The diagram should include a schematic outline of the electron transport chain and the ATP synthase. In the discussion it should be mentioned that NADH is oxidized by complex I, and electrons are
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This note was uploaded on 12/30/2010 for the course BIBC 102 taught by Professor Scheffler during the Spring '10 term at CSU Northridge.

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FINAL SU06.2ANSW_2 - 9/2/2006 11:08 AM METABOLIC...

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