Midterm Exam 1 Solution - Structure and Function of Biomolecules | BIS 102, Exams of Biology

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1 of3 BIS 102 Name Kew Fall, 2012 Last 7 First K. Hilt First Midterm Score (100): Equations: pH = pK, + log {{bJ/{al} (Ky) (Kx)=1x10" Kp=x'/(y-x) Ke=x'/(y-x) pH = (Ka, + BKa,)/2 F=q@q@)/er AG=AH-TAS pK,’s of amino acid side chains: _D (3.9), E (4.2), H (6.0), C (8.3), ¥ (10.1), K (10.5), R (12.5) pK, of amino acid o-~COOH (2.1); pK. of amino acid a-NH;" (9.6) pK, of oligopeptide N-terminus (7.4); pK, of oligopeptide C-terminus (3.6) 1, (10 pts.) What is the final pH when 400 ml of 0.20 M NaOH is mixed with 0.150 liter of 0.100 M H3PO4. Show all calculations. The pK,’s of H3PO, are 2.12, 7.21, and 12.32. (0.400 2)o.20 4 Nad) = 0.0% mek o#~ (0.150 2)(0,100 H3 004) = 2.0/5 moh M3? O, 2, 3 (0. 015 mek} = 0.045 me of needed -2 1238 -3 ea ~|) wz 3 P04 ae Ha tug! oe HPO * (24; 0. 08 me an poke tO -0., 04S wh Of ~ ot +, 4.035 mol ot lett over 0.035 ml bt = 0. O36 M OH pO - lon 4. 0b 36 = 1.196 O.5 50 X pi = W119 3G 8) 2. (10 pts.) Calculate the pH of 100 ml of 0.25 M amine solution that has a pK, of 9.63. Show all calculations. x Fully unpretonacte f nezd Ky gation e J ae ekat eky= ih Ky = ae Ky = 4.37 =-loy Ke Ky 27 KS = 3.267% )0 °M = of poH = -leg 3.267 #72 22.4958 ph = -2485e =@5) 3. (10 pts.) Imagine that you are a molecule in the cell cytosol, at pH 7. Off in the distance is a valine molecule that is approaching. Describe, on the molecular level, what that valine looks like as it approaches you (i.e. charge, etc.). In addition, describe what weak bond interactions it can make with you. }. The vale net chavare isto" 2. Heh Sorm a clatvete around the side wen Ub form shells 3. 205 form Hebonds te the o- Ny” andi «Cor. \ Cod both. yo vthe valine can make oa ny drephobic interaction , a H-bmd interaction , and a van dey Wacla jwlerachion uatth you.