exam 2a 2009 - no answers

exam 2a 2009 - no answers - WRITE YOUR NAME LEGIBLY ON...

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WRITE YOUR NAME LEGIBLY ON EVERY PAGE NAME (print, no nicknames): CHECK TO BE SURE YOU HAVE 7 PAGES INCLUDING COVER PAGE. I swear/affirm that I have neither given nor received any assistance with this exam. Signature: Date: BIOCHEMISTRY 460 EXAM 2A March 9, 2009 Read each question carefully Please put your name on every page.
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Name (print, no nicknames) __________________________________________ ‐ 2 ‐ Total_____________ BE SURE TO STATE UNITS OF ANY NUMERICAL ANSWERS. NO CALCULATORS ARE PERMITTED ON THIS EXAM 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.) 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 in peptides & proteins (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 Unless otherwise stated, assume the following ion concentrations “under normal physiological conditions” Ion Cytoplasmic Exoplasmic Na+ 12 mM 145 mM K+ 140 mM 5 mM p. 3 (17)____________ p. 4 (24) __________ p. 5 (25) ___________ p.6 (13)_____________ p.7 (24) ____________
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Name (print, no nicknames) __________________________________________ ‐ 3 ‐ Total_____________ Problem 1 (17 pts) A) 2 pts Which of the following sequence would chymotrypsin hydrolize? 1. GLY-ALA-ASP-LYS-ALA 2. ARG-VAL-SER-CYS-GLN 3. ALA-GLY-PHE-ASN-MET 4. none B) A team of researcher has discovered 2 new serine proteases SERPRO1 and SERPRO2 highly homologous to chymotrypsin. The molecular basis of substrate specificity was explored using site-directed mutagenesis and kinetics studies. Mutant SERPRO is a variant of SERPRO1 where a few of the amino acids have been changed Kinetics experiments were performed for each enzyme with two different substrates (SUB1 and SUB2) Assume for all of these enzymes that K m is approximately equal to K ES (the dissociation equilibrium constant for the ES complex). 1) 2 pts Which enzyme has the largest catalytic turnover for SUB1? Why did you give that answer? 2) 2 pts Which substrate (SUB1 or SUB2) does the
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This note was uploaded on 05/06/2010 for the course BIOC 460 taught by Professor Ziegler during the Spring '07 term at Arizona.

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exam 2a 2009 - no answers - WRITE YOUR NAME LEGIBLY ON...

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