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Exam 1 2007 BLANK - Biochemistry 441 1st Hour Exam Feb 7...

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Biochemistry 441 1st Hour Exam Feb. 7, 2007 Name_______________________________ Student #________________ The exam has five pages, each worth 20 points. [The numbers in square brackets are the points for the individual questions.] 1. Fill in the blanks: (A) Leptin inhibits fatty acid biosynthesis by triggering a process that promotes phosphorylation of acetylCoA carboxylase (or biotin carboxylase-transacetylase ) [1]. (B) Aspirin inhibits both isozymes of cyclooxygenase [1]. (C) Glucagon inhibits synthesis of cholesterol by promoting phosphorylation of HMGCoA reductase [1], which catalyzes the following reaction [draw the structures of the metabolite reactant(s) and product(s) and give the names and stoichiometry of any coenzyme reactant(s) and product(s)]: _________________________________ [4] _____________________________________ [4] Cholesterol also controls this reaction by decreasing expression (or transcription ) of the gene for HMGCoA reductase [1] and by promoting proteolysis of the enzyme [1]. (D) Homocysteinemia can result from a dietary deficiency of either vitamin B12 [1] or folic acid (or folate ) [1]. (E) The fatty acyl chain is attached to the ACP (or acylcarrier protein ) [1] domain in most of the steps catalyzed by the mammalian fatty-acid synthase. It transfers to a cysteine [1] residue in the β -ketoacylsynthase [1] domain for the chain-elongation step. (F) In E. coli , glutamine synthetase is regulated partly by covalent attachment of a/an adenylyl [1] group to a tyrosine [1] residue. p. 1 p. 2 p. 3 p. 4 p. 5 Total CO-SCoA CH 2 CH 3 CO 2 - CH 2 HO C CH 2 OH CH 2 CH 3 HO C CO 2 - CH 2 + 2 NADPH + 2H + + 2 NADP + + CoASH
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2 2. Fill in the following table comparing citrate synthase and citrate lyase with regard to intracellular location and the reaction each enzyme catalyzes. (You may identify the reactants and products of the reactions by name; you don’t need to draw their structures.) Enzyme Citrate Synthase Citrate Lyase Location mitochondria [2] cytosol [2] Reaction acetylCoA + oxaloacetate citrate + CoASH [3] citrate + CoASH + ATP acetylCoA + oxaloacetate + ADP + P i [3] 3. You are investigating compound I as a drug for cancer chemotherapy. The drug is broken down in the liver by a pathway that begins with conversion to the inactive compound II. Below the curved arrow, write the names of the molecules that you would expect to be the other reactant (A) and product (B) of this reaction.
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