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BIOC 460 Exam 2 - 1 BIOCHEMISTRY 460 SECOND HOUR EXAMINATION – June 18, 2007 ANSWERS WRITE YOUR NAME AND I.D. NUMBER LEGIBLY ON EVERY PAGE CHECK TO BE SURE YOU HAVE 7 PAGES , INCLUDING THE COVER PAGE. I swear/affirm that I have neither given nor received any assistance with this exam. Signature: Date: A NON-PROGRAMMABLE CALCULATOR MAY BE USED ON THIS EXAM. No programmable calculators are permitted, and no sharing of calculators. We have a couple of spare calculators to lend in an emergency. SHOW YOUR WORK FOR ALL CALCULATIONS , AND BE SURE TO STATE UNITS OF ANY NUMERICAL ANSWERS. If the reasoning, calculations, or answer are shown anywhere other than in the space provided, make a note in the space provided and put answer on BACK OF SAME PAGE so the grader for that page will have it. USEFUL CONSTANTS : R (gas constant) = 8.315 J •mol –1 •Kelvin –1 = 8.315 x 10 –3 kJ •mol –1 •Kelvin –1 If temperature = 25 °C, absolute temperature T = 298 K (Assume this temperature unless problem states otherwise.) F ( Faraday constant ) = 96.5 kJ/(V•mol) Potentially useful equations : Michaelis-Menten Equation: V o = V max [S] [S]+ K m Free energy of transport: G t = RT ln C 2 C 1 + zF V where F is the Faraday constant (96.5 kJ/V•mol), z is the charge on the solute, and V is the membrane potential (charge gradient across the membrane) Use these “generic” pK a values only when no precise pK a for a specific group is given. Ionizable group in peptides and proteins Approximate ("generic") pK a (from Berg, Tymoczko & Stryer, Biochemistry , 5th ed., 2001) α -carboxyl 3.1 side chain carboxyl 4.1 imidazole 6.0 α -amino 8.0 thiol 8.3 aromatic hydroxyl 10.9 ε -amino 10.8 guanidino 12.5
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BIOC 460 Exam 2 - 2 1. (4 pts) What binds in the “oxyanion hole” during chymotrypsin catalysis? A. the imidazole group of the active site His B. the nucleophilic negatively charged oxygen on the active site Ser C. the negatively charged oxygen on the tetrahedral intermediate D. the oxygen atom of the substrate’s carbonyl (C=O) group with the double bond to the O E. the hydrophobic or aromatic R group of residue preceding the peptide bond to be cleaved F. the carboxylate oxygen of the active site Asp 2. (6 pts) The general reaction catalyzed by protein kinases is: Protein– OH__________ + ATP_ _____ Protein– O-phosphate (O-PO 3 2- ) + ADP (protein functional group) (2nd substrate) (modified functional group) (2nd product) 3. (3 pts) Coconut oil contains only a very low proportion of unsaturated fatty acids (FAs). It still has a low melting point because: A. it contains a lot of short-chain fatty acids. B. it contains a lot of long-chain fatty acids. C.
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