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Key Mid 1 Fall 2009

Key Mid 1 Fall 2009 - lofl BIS 102 Name K3 Fall 2009 Last...

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Unformatted text preview: lofl BIS 102 Name K3; . Fall, 2009 Last First K. Hilt First Midterm Score (100): Equations: pH = pK, + log {[b]/[a]} K, = 2/(y—x) Kb = x2/ (y-x) pH = (pKall + pKa2)/2 (K,)(K,,) = 1 x 10‘‘4 Amino acid pKa’s: a-carboxyl group (2.1), a-arnino group (9.6) side chains: D (3.9) E (4.2) H (6.0) C (8.3) Y (10.1) K (10.5) R (12.5) Oligopeptide pKa’s: C-terminal carboxyl group (3.6), N—terminal amino group (7.4) 1. (10 pts.) In the space below, calculate the pl of glycine and draw the complete structure of the form of glycine that would predominate at this pH. ,. eye 2 . 1 + a. b \ i L 1437" ‘ + 7 H A’ 3 2. (20 pts.) How many moles of HCl are required to lower the pH of 4.00 liters of 25 mM glycine, pH 9.50, to a final pH of 2.40? Assume that the addition of HCl does not change the volume of the solution. Put your answer on this line: 0. 0 “7 2 mols of HCl. To receive credit, show all of your Work on the back of this page. 3. (20 pts.) Give the one letter code of Ll] of the amino acid R—groups that satisfy the following statements. Put your answer(s) on the line after each statement. However, do not guess. Points will be subtracted for wrong answers. + 1 a) R-group has an amino group K + 1 b) R-group has an imidazole groupmm H + 2 c) R—group IS an amide QM + 2 d) R—group reacts with 02 C. 1- 1 e) R-group is three reduced carbons (no other atoms) P \/ + 2. f) Regroup has an asymmetric carbon I T + 3 g) R-group absorbs UV light W ‘1’ F +5 h) R-groupisaH-bond donoratpH 10 N T 14 K 1—1 \( c. w (”Jack 1— 2 i) R-group will have the greawst number of waters forming a elathrate ardund it ‘— 4. (30 pts. ) Draw the complete structure of the following peptide, in the form that would predominate atpH 12: H— P— Q0— N— W— K— E a 0 ,4 0 +091 laud/1. ‘IL 101 101 1 101 i1 1‘ If 1' ‘14. I? 1 ll - {22TH carver/4') z +‘-{ We-“ we: 04% e—c—e-«Te t- wed—7's. -¢-~—¢re'° L L», \c /c. r1 011, H (1142 H a», 1+ Lena) H (.142 ““2”“ z = +5’ 1“” \L \CH 1 l , ll" ‘4" G 2 L:o C..:.¢ N42 4'. 2 5. (20 pts.) Using the axes below, draw in the elution profile that would result if amino acid analysis was done on the peptide in question #4. Label the axes, the elution buffers, and each peak. Draw the positions and shapes of your peaks carefully +1 .11 3] a 3:7 N rib/ak— Ole-i‘foii ”a“ ‘I on t H 0.7. M i 00 0.33 L!” H‘ in ~9W 6W ...
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