Exam 1 - Fall 2013 - Key - BIOCHEM 301 FALL 2013 EXAM#1...

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BIOCHEM 301 FALL 2013 EXAM #1 Friday, October 4, 2013 — 75 minutes 100 points possible Name (print and sign): I certify that I have followed the Duke Community Standard in completing this exam—meaning, among other things, that these answers are my own work, and that I have not used any unauthorized aid. 1. Phenylalanine, tyrosine, and tryptophan are three of the 20 common amino acids used by all organisms. a. In the space below, draw the structures of Phe, Tyr, and Trp as free amino acids at pH 11. Label each amino acid with its name. (12 points) b. How many protonation states would each of these have as a free amino acid? (3 points) Phe Tyr Trp c. How many protonation states would each of these have as part of a polypeptide? (3 points) KEY 1 2 1 H 2 N H C COO - CH 2 H 2 N H C COO - CH 2 O - H 2 N H C COO - H 2 C HN phenylalanine tyrosine tryptophan
BIOCHEM FALL EXAM 2 d. In a folded water-soluble protein, would you expect these amino acids to be found in the interior of the protein, on the exterior, or potentially both? Circle all that apply. (3 points)
e. All three of these amino acids could be used as part of a binding interface in a protein active site. In what kinds of noncovalent interactions could each amino acid participate? Circle all that apply. (3 points)
f. Could each of these be used as part of an arrow-pushing catalytic mechanism? If so, circle the applicable types of catalysis. (3 points)

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