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BIS 102 Name _____________________________________________
Summer, 2009 Last First
K. Hilt
Final Exam Score (200): ___________
Equations: pH = pKa + log {[b]/[a]} Ka = x2/(y-x) Kb = x2/ (y-x) pH = (pKa1 + pKa2)/2 (Ka)(Kb) = 1 x 10-14
F = (q1 q2) / r2 G = H - TS vo = {Vmax [S]}/ {Km + [S]}
Amino acid pKa’s: -carboxyl group (2.1), -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. (25 pts.) How many moles of HCl are required to change the pH of 300 ml of 0.200 M histidine buffer, pH 9.8 to a
final pH of 2.6? Assume that addition of HCl does not change the volume. Put your answer here: _________ mols
HCl. To receive credit, show all of your work on the back of this page.
2. (25 pts.) Crystals of deoxy Mb are stored in a N2(g) atmosphere. If O2(g) is added, nothing happens to the crystals.
However, when crystals of deoxy Hb, stored in N2(g), are exposed to O2(g), the crystals shatter. Explain what is going
on (i.e. “Why are the two outcomes different?”). Give a detailed answer.
3. (20 pts.) 200 ml of 0.600 M NH3 is mixed with 400 ml of 0.100 M HCl. What is the final pH? The Kb of NH3 is
1.80 x 10-5. Put your answer here: pH = _________. To receive credit, show all of your work on the back of this page.
4. (40 pts.) Chymotrypsin cuts on the carboxyl side of aromatic amino acid residues. Draw the active site of this
enzyme, using chemical structures (you do not need to draw the substrate). Label each part of the active site. Explain
briefly what each part is doing during catalysis. Points will be given for the clarity of your drawing and your
explanations.
