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CHEM 109C – Zhang
Amino Acids I: Structure and Properties - KEY
CLAS, F10
It would be good to review the 20 essential amino acids!
1. What is the absolute configuration (R or S) at the -carbon in each of the
enantiomers of Alanine? Are they D or L amino acids?
2. Which isomer (R)-Asp or (S)-Asp is D-Asp?
3. Name an amino acid besides threonine = Thr that has more than one asymmetric
center.
4. Lysine has the following pKa’s -COOH = 2.18, -NH3+ = 8.95, side chain, R =
10.79. Draw principle species at each of the following solution pH’s: 0, 4, 10,
and 13.
5. Calculate the pI of
a. Lys
b. Asp
6. Which amino acid has the highest pI value?
7. Which amino acid has the greatest amount of negative charge @ pH = 6.20?
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