Exam 1 2009 BLANK - Biochemistry 441, 2009, 1st Hour Exam...

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1 Biochemistry 441, 2009, 1st Hour Exam Name ______KEY __________________________________ Student Number ___________________________________ The exam has seven pages including this page. page points 2 /16 3 /18 4 /18 5 /18 6 /13 7 /17 total /100
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2 1. (6 points) You find a strain of E. coli whose phospholipids contain unusually large amounts of lauric (C12:0) and myristic (C14:0) acid relative to palmitic (C16:0) and stearic (C18:0) acid. You realize that this could result directly from a mutation in either of two enzymes of lipid metabolism. Write the reactions catalyzed by these two bacterial enzymes. RCO-S-ACP + Enz-SH RCO-S-Enz + ACP-SH RCO-S-ACP + H 2 O ACP-SH + RCO 2 H (or RCO 2 - + H + ) R = CH 3 (CH 2 ) n CH 2 -, Enz = β -ketoacyl synthase, ACP = acyl carrier protein 2 . (10 points) Briefly summarize the main mechanisms of control of fatty acid biosynthesis in mammals. The main control point is acetylCoA carboxylase (biotin carboxylase/transcarboxylase). The enzyme is activated allosterically by citrate (and also isocitrate) and inhibited allosterically by palmitoylCoA. It also is inhibited by phosphorylation. Phosphorylation (inactivation of the enzyme) is promoted by glucagon, epinephrine, adiponectin and lectin. Insulin promotes dephosphorylation (activation).
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3 3A. (6 points) What three main groups of compounds act as carriers of reduced 1-carbon units in metabolism? S-adenosylmethionine Tetrahydrofolate (THF) Cobalamin coenzymes 3B . (6 points) What are the two main dietary sources of reduced 1-carbon units for mammals under usual conditions? Serine and glycine 4. You are studying the formation of urea from glutamate and alanine by liver cells. You break the cells by gentle homogenization at 5 ° C, centrifuge the homogenate at low speed (1,000 g ) to remove plasma membranes and unbroken cells, add Glu, Ala and/or Arg to the supernatant in various combinations as indicated in the table below, and measure the rates at which urea is formed. experiment additions urea ( μ mole per minute per mg protein) a glutamate (1 mM) + alanine (1 mM) + arginine (0.1 mM) 40 b glutamate (1 mM) + alanine (1 mM) 1 c alanine (1 mM) + arginine (0.1 mM) 1 d glutamate (1 mM) + arginine (0.1 mM) 5 A. (6 points) Why is the amount of urea formed in experiment a much greater than that in experiment b ?
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This note was uploaded on 02/02/2010 for the course BIOCHEMIST Biochem 44 taught by Professor Parson,young during the Winter '10 term at University of Washington.

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Exam 1 2009 BLANK - Biochemistry 441, 2009, 1st Hour Exam...

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