Spring 2007 MT1

Spring 2007 MT1 - lof2 BIS 102 V Name m Spring, 2007 TuTh...

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Unformatted text preview: lof2 BIS 102 V Name m Spring, 2007 TuTh Last First K. Hilt First Midterm Score (100): Equations: pH = pK. + log {[b]/[a]} K, = 2/(y-x) Kb = x2/ (y-x) pH = (pKal + pKa2)/2 (Ka)(Kb) = 1 x 10‘’4 F=(ql (15/812 AG=AH-TAS 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 pK,’s: C-terminal carboxyl group (3.6), N-terminal amino group (7.4) 1. (13 pts.) Which amino acid has a net charge of approximately “-0.14” at pH 7.5? Give your reasoning and show all necessary calculations. Then draw the structure of this amino acid that would predominate at this pH. pH '75 is MWM l end/141.43 M 1"“- chL's of: 1%.: 03:003de oL'I-Jfis W, a“ w!" M oL'UH3+ W.3m .. —. a . l M, Wer’QH‘ZrQ) “ewe—‘3- 4' -L-H ,5": 5’3 + / A . [La/U cl,” 4,11 7 k 7’ q " ‘9: '—L—- : 0,135 $5} 0_ f- _. I 3 (0_13(,)(—)) E- —-0.l‘-f *é. ' lo 2. (20 pts.) How many moles of KOH or HCl WO (1 be required to change 300 ml of 0.100 M arginine solution with a net charge of “-0.65” to a net charge of “+1.35”? Show all calculations. 4.. (0.3L)(o.. r4) = 0.03 5 4” (0.090103 We): 0. on; M H (SW-K M z .- ¢90H . + \vu 12.5 wfflw 9”“ + 3'— a 'Z—— O——- L. 0): (0.5:)(ooswe—F p.03m2 0+ ’0“- + 0105*“2 2,50”: 0 "V imp + + 0 nc :47; H 0 _‘ W 35 a £57.: M0 k .. nc 4mm”) + (MW!) " M ‘ "M -.-. o '1 + o by 3 .‘p ~ +- +3 *3 .— L35 17411 ’1‘ ' 049/0534“? + 0.03 "we + aome 1 0. 00 me H'+ HI 3. (5 pts.) What is the approximate pH of a 3.45 x 10'12 M HCl solution? Give your reasoning and/or calculations. H+ ‘ ‘ H 0 \ QH '7 Mvamc Mm munj ream 2,] ma, 1 x. )0 M [4+ . 20f2 BIS 102 Name ___g___________ 4. (15 pts.) What is the final pH of a solution obtained by mixing 300 ml of 0.40 M NH; with 200 ml of 0.20 M HCl? (Kb = 1.80 x 10'5 ). (deco/@040 M #14,) = 0.12 Na pH, (0-3”£)(0.20M #00) :; 0,04 Ne (4+ 0.0; ME NH; 0. 01-] m6 NHH.’ [12) Kbsl.?otc/o'r eHrtrqK’m'l' 101:3 (47 K v 1' H.7Li 5 0. 05’ +5. GK 7-26 + h; a0st 5. (20 pts.) Draw the complete structure of the peptide P—H—G—Y-T-W, in the form that would predominate at pH7. 9 0 0 0 t? '3 u If I' If I‘ ('3. u 7" —- ¢~I~J~ o»- oau'o-¢—— u—c... c—u- c— ¢~N..¢,.. an: 4— c/ l I \ \ l I l I ’ l H,/~i/ x“ H 0‘”: H H H at; Hu-c‘—DH H a“: z N l l / c/ \ /\ cu c=¢ Hf"¢“z u If \\0 ‘3 \ ‘10 OK” C—v—é z) +3 13 ac“ dam/914v *3 I 6. (27 pts.) Answer each question on the line provided afier it. If an answer involves an amino acid, use its one-letter code. If a question has more than one possible correct answer, then give them all. However, do not guess. Points will be subtracted for wrong answers. col/k *9 a) Which of the four weak bonds is the weakest? VAM 9.0V Max:011. b) What characteristic, other than high concentration, makes for a “good” buffer? pH ~ 2 Kg 3 no Mum c) What compound is added to small aliquots from each collected test tube from an ion exchange column, to detect amino acids as they elute out? rt in L1 évtk (1) Which amino acids have an amide in their side c ain? 92 A} e) Which amino acid has a guanidino group in its side chain? g f) Which amino acid is actually a secondary amine, rather than a primary amine? P g) Which amino acid(s) has/have more than one amino group in it? E h) Which amino acid(s) has/have a side chain that can absorb UV light? kl Y F: i) Which weak bond becomes stronger when the solution temperature increases by 5°C? ...
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This note was uploaded on 04/08/2008 for the course BIS 102 taught by Professor Hilt during the Spring '08 term at UC Davis.

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Spring 2007 MT1 - lof2 BIS 102 V Name m Spring, 2007 TuTh...

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