BIS102 Hilt F08 MT1

BIS102 Hilt F08 MT1 - lof2 BIS 102 Name Fall 2008 Last...

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Unformatted text preview: lof2 BIS 102 Name % Fall, 2008 Last First K. Hilt First Midterm Score (100): Equations: pH = pK. + log {[b1/1a1} K. = x2/(y-x) Kb = le (y-x) pH = (pKa.l + pKa,)/2 (K.)(Ku) = 1 x 10'“ 1==(q‘q’)/er2 AG=AH-TAS Amino acid pK.’s: a-carboxyl group (2.1), a—amino 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 pK.’s: C-terminal oarboxyl youp (3.6), N-terminal amino group (7.4) This exam is all about the pentapeptide P-Q-H-K-C. l. (25 pts.) Draw the complete structure of PQHKC in the form that would predominate at pH 7.5. o .4 D H . . 3_ {C3 _'.’ _ /c—N..¢_C,.—H—c,-c, til—c. c’@ (1...; 0 C \ m <11 @ @ +5“ charges c C W C +15 5m res @ \6 («Vb-havewk) 2. (5 pts.) On your structure in question #1, very carefully circle a]; of the atoms that can participate in hydrogen bonding. M W rte, circela. , + 0- 5' e acct 3. (4 pts.)0nyourstructureinquestion #1,very carefirlly put rectangles around all ofthose atomsthatcan haveclathratesofwaterformaroundthem. 3 1409 M -— 9“)“ W‘“ “'5- ‘P: Go" ‘4: M W 1947484— max-lee.— minof mHibuHM$1+l '1" H H 4. (15 pts.) Calculate thenetcharge, to thenearest0.01,forthe pentapeptideatpfl 7.5. Put your answer on this line: 0.33 .To receive credit, show yourwork on the back ofthis page. 5. (8 pts.) 0.100 moles of fully protonated pentapeptide PQHKC were put into 0.500 liters of water. What is the final pH of this solution? Put your answer here: pH = ‘2 . I . To receive credit, show your work on the back of this page. 6. (8 pts.) Using the axes drawn below, carefully sketch in the titration curve for this pentapeptide. Label the axes. Clearly label the points of interest along this titration curve with pK.’s and the organic group responsible for each. (Your answer for question #5 gives you the starting point fig '5 curve). gins]: “8‘ D k ww¢ (5‘3 W“ H 549‘wa we, «the. M 4“, mm had: 20f2 BIS 102 Name Egg 7. (6 pts.) When you have pulled ofi‘ the last proton fiom the pentapeptide solution in question #5, what will the final pH be? Put your answer here: pH = H .‘I ,To receive credit, show your work below. PKa/z (0.5 [LI—[0.57— fzb '5 3,5 ‘3 5 = — \0'1}, Kb —‘I {IL Kb — 3.15 up = 13:. Kb gfi :— '3 .. 3.ILXID’”= “ x214“! Ho Hslon *2“ 0.7. .— 4r7/ PDH ’— ’Z.. D‘T‘f .'. 9H - 8. (15 pts.) Imagine that your solution in question #5 had OH' added to it to raise its pH to 5.8. Now the question is: “How many moles of OH“ would be required to raise the pH fiom 5.8 to pH 10.6?” Put your answer here: 0 — 3 7— mol OH'. To receive credit, show your work below. UN?— wid’VG-ARM MW in MM *6. Meta ’rwo (he. +5{0,Zw\fl€1¢ OH— 3“” m Mien/Wale}, $44—94 wmk M 4—1,“, “.44 QQQ¢$‘ waeKa+lwk‘% (’V‘r‘924—4'Wab; 53’ = 6-D + lag/lg: 10.4, :: w.5’+ Iv} 5‘: '0‘; = '0‘},ka 0.\ = log, a: , 2 Jo. . -_L___., 1.;5‘7 _ , _:.258 L” 0» " 0" 0'5) a—v %' n. b" 2.2;? I t __ = 0.55?— (a.bn)(a.l m2) — L0, 55002.1 MC), 0.051. 4—1-1 rune, 0*" +4 7/0411 mag/ca 3h‘-: 0,05] + 0.] + 0.! + 0.056: 0.3!?— +2.. 9. (6 pts.) At what pH will the pentapeptide PQHKC not move in an electric field? Put your answer on this line: pH = 7.?5 . To receive credit, show your work on the back of this page. Wrms flags two/an 1/2 \OVflQH' '19- +3 10. (8 pts.) Amino acid analysis was done on this pentapeptide, using the column discussed in class. Using the pH 3, 4, and 5 bufi‘ers, diagram the elution profile that you would expect to see. Label the axes, elution (“€53 pH’s, and peaks. Draw the location and sizes of your peaks carefully. “no 5 Q“, '3 p p} \.( P H r K ’2' l x x EM 8 +kc— «Di-(«Mrs we’ruhir W +| fiw and. “$14, ‘ nucleon q, gm “1:”: 4. (H N Tux—9 WM) 0% l W +\ @01- Wis Mods Mk) Ora-a” +1 flaw K bag“ 21.“ em si‘u, ...
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BIS102 Hilt F08 MT1 - lof2 BIS 102 Name Fall 2008 Last...

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