Chem 336 - Spring 1999 - Organic Chemistry III
Portland State University - Dr. Carl C. Wamser

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Chapter 27 Quiz Answers

1. (3 points) Write the structure of the tripeptide GlnArgMet as it would appear in aqueous solution at pH 7.

2. (4 points) Using only the side chains of common amino acids, illustrate each of the following types of interactions. Show the full side chains and identify the amino acids you used for your examples.

a) a disulfide bridge

Cys-Cys

b) electrostatic attraction

Asp - - Lys

there are also several other possibilities

c) hydrogen bonding

Glu - - Thr

there are many other possibilities

d) hydrophobic interactions

Phe - - Trp

there are many other possibilities

3. (3 points) Identify the amino acids in glutathione, writing them in the standard way from N- to C-terminus. Identify an unusual feature of this common tripeptide.

The amino acids are Glutamic acid, Cysteine, and Glycine. The unusual feature is that the Glutamic acid is joined in a peptide bond at the side chain carboxyl rather than the alpha-carboxyl.