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Reading Guide, Stryer Short Course, Chapter 3
1. Why do amino acids exist in D and L forms?
2. Why do amino acids exist as zwitterions at physiological pH?
3. Your book lists four classifications of amino acids. What are they?
4. How is proline unique as an amino acid?
5. Name two hydrophobic, aromatic amino acids.
6. Where do the hydrophobic amino acids of a protein tend to cluster?
7. Name three amino acids containing a hydroxyl group in their sidechains.
8. Which is more reactive, serine or cysteine? Explain.
9. Name two amino acids with amide sidechains.
10. Name the amino acids that are commonly positively charged at physiological pH. Which one
of them can also often be neutral in a protein depending on the local environment?
11. Why do glutamate and aspartate end in the suffix “-ate”?
12. Given the one-letter abbreviations of the amino acids, draw their structures and give their
three-letter abbreviations.
13. Refer to Table 3.1 to draw aspartate, histidine, and tyrosine in their most prevalent ionization
state or states at pH 1, pH 3.3, pH 6.0, pH 10.9, and pH 13.
14. What is an essential amino acid? What disease can arise from improper intake of protein in
the diet?