Key Mid 1 Summer 2010

Key Mid 1 Summer 2010 - lof3 BIS 102 Name K% Summer, 2010...

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Unformatted text preview: lof3 BIS 102 Name K% Summer, 2010 Last First K. Hilt First Midterm Score (100): Equations: pH = pK. + log {rm/[an K. = xz/(y-x) Kb = x2/ (y-x) pH = (PKal + PKa2)/2 Amino acid pKa’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 pKa’s: C-terminal carboxyl group (3.6), N-terminal amino group (7.4) 1. (30 pts.) Draw the complete structure, in the form that would predominate at pH 7, of the following oligopeptide: P—N—W—H—I—C—T-K / \ \ \ 5 3 \ 14¢ ' \ H C Lu 2, N“; /c__..c'/\ 3 +2. 41 4,.2 +2 +2 \ / +3 +2 +3 QMMQSLS: 4—5 (N-klumuf, c'h‘wflwp swig dad”, 4» H. (1' M. K) 9e,th had/l 2 +7 2. (10 pts.) Calculate the net charge of the peptide in question #1 to the nearest 0.01 . Show all calculations. - .1 as. 4...; PM?” 4 73“? f"=e"~x+”?rr‘<%3 r; I; 7.4 +:u .52 b- “ ’7 3 9.3 + In? a _.s7.‘l:i a V‘ Mpg z: 0 3‘“ L 2'. «L -+ .1141 f 1 ‘ “c2 0‘ 13m 0 9-3:: .19, b: 0.495" “ii—:09 +3 I k ’ 05' ' +3 K m1?- olam“ QTTEE’W“WLW H 5.31 attain» w 4-: ”' g“: r‘<¢ 4- \0'3 (47 H H 7.0: 4.0 + tax) a; me. u: amt -—:—= 5.1.? '5 "5% J- LQ_= h, ‘0 a: = +2. 1 6-— 3.1 mm mm a m +0.04: m»; «if 3. (5 pts.) On your peptide structure in question #1 above, carefully draw in one peptide bond plane, using a rectangle. Then explain here, briefly, why those atoms are in a plane. K 4, asl-oms in m plane. fO—Sancwu + 3 +1 20f3 BIS 102 Name K% 4. (8 pts.) What is the final pH when 250 ml of0.35 M NH; is mixed with 300 m1 of0.20 M HCl? (Kb = 1.8 x 105). Show all calculations. Lo. :50 Ryaasu nus) = o. 087$ we Nils} H (0.300230.” M Ha) =o.0eo M W” +- AM M3#nc) —-—» 0.0215 mafl NH.3 +. 9.060 «we HHH Hz: Ma»: 1 311 ‘ 4+ 6 6’ “a La} #5504 comm: “ '° _w = £1.24, +c “our: __._—— ‘4«=5-5‘5*I0 ’3 0.060 rue/m»! .'. e2“: —\03 K 29.14 —_ a.» + (- 0.33%?) +7. :' fig; 6,: +3 5. (5 pts.) What is the approximate p ' of a 3.5 x 10"1 M HCl solution? Give your reasoning and/or show calculations. Q” 7 11m. mewlcvd-im 4 \4" Wle va 11-10, 111.0114. +7- 16 Minis Trench-ex. +3 6. (15 pts.) How many moles of OH- are required to raise the pH of 500 ml of 20 mM phosphate buffer, pH 2.35 to a final pH of 12.1 ? Assume that the addition of OH- does not appreciably change the volume of the solution. The pKa’s of phosphoric acid are 2.12, 7.21, and 12.32. Show all work. {0'5w52\)(0-010M eWkdi): 0-010 may; “cc-what“ +‘-l +4 Wt nag (0.37) +0» + (0.315) =- |."I‘l'3 e1»va 1:“, m4" owwo M = +3 +'.-l 3of3 BIS 102 Name K 3:3 7. (5 pts.) The strength of one of the four weak bonds depends on the temperature of the solution. Which weak bond is this? Explain how temperature is a factor. (Do not use an equation in your explanation). Mam,ko «HA, M a. “+0 44a. {law 4.2. Avis Jar l-l O Vida is ,2; Mi 5;? W W 8. (5 pts.) Direction plays a part in the strength of one of the four weak bonds. Which weak bond is this? Explain why direction is a factor. 4" MW wot, Math 4 «a. hm! us mm; own? 4, *L bwdl arM’i’wQ-o in W hawk. W aw w. «3qu (diuretic/A it... deems, +2 9. (10 pts.) The amino acid cysteine may be oxidized by exposure to oxygen in solution, to form the compound cystine. In the space below, draw the complete structure of cystine, in the form that would predominate at pH 7. Then show how excess mercaptoethanol (draw its structure) converts cystine back to two cysteines. Draw out all structures and clearly show the reaction sequence of how cystine is converted to two cysteines. Include all products. cot-0' fia‘m‘ C(m’ 4— tin“ “a; .‘w: @«cfl + H5 with” saga-H + “5”; H ‘ I. CH (Kt-l1 (it: +I ‘6‘; \$_S'CH20A 5' H mam +1 insulchon +1 okarsés +l can" i Hypo—H 4, S“ Oriya-lon \ CI”: 5—ca—lz «4+!on 64-} +2. +l 10 (7 pts.) 200 ml of 0.10 M acetic acid (pKa 4.76) is mixed with 150 ml of 0.05 M ethanolamine (pKa 9.44). What is the final pH of the mixture? Show all calculations. (LazmllYo. IO M) = 0,02,.9 Me (243400” (a. 15—0 2)(o. 050 H) : o. 0075 M "ya-Irony” A34!» wiring, Me Mr: mar/{Ml 04300" 4.. 0.19:2; Nut—Q “43%;; 0. 0075 “2/350 ,1 9” Q + a3\(‘\‘\ LL76+ In} a.aaz$m(/3yvm2 = um. 4» (.mg @q ...
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Key Mid 1 Summer 2010 - lof3 BIS 102 Name K% Summer, 2010...

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