FCH 530 Homework 1
1. The -carboxyl group of Glu has a pKa of 4.3.
a. What fraction of the -carboxyl groups will be unprotonated (i.e., -COO- rather than –
COOH) in a dilute solution of Glu at pH = 5.0?
b. At pH =3.8?
c. explain why this -carboxyl pKa is higher than the pKa of the -carboxyl group.
2. Calculate the pH of the following: 0.1 M HCl, 0.1 M NaOH, 3 X 10-5 M HNO3, 5 X
10-5 M HClO4, and 2 X 10-8 M KOH. Show all work.
3. Draw the structures, full names, three-letter names, and 1-letter symbols for all 20
amino acids. Indicate the pKas for each of the functional groups on each amino acid.
4. Draw 4 equivalent Fischer projection formulas for L-alanine.
5. For the dipeptide Glu-Ala write out the structure and estimate the pK of all ionizable
groups.
Using your assigned pK values, determine the net charge at pH 1, 3, 5, 7, 10, 11
Calculate the pI of this dipeptide.
6. Write a table describing the main differences between gram-positive and gramnegative bacteria?
7. Write a table summarizing the main differences between prokaryote and
eukaryote cells
8. Draw the following amino acid or oligopeptide structures:
a. The dipeptide Ala-His
b. The tripeptide Glu-Pro-Cys
c. Show how an oligopeptide of Leu and Lys can be either a branched-chain or a
straight-chain structure (only straight-chain structures occur in most natural
proteins).