CHAPTER 6 AMINO ACIDS IN PROTEINS Objectives: 1. What is the approximate pKa for all alpha-amino groups and for all alpha-carboxyl groups? Are they charged at pH=7? 2. Which stereoisomer is most prevalent for any amino acid, the D- or the L- form? 3. Be able to recognize a peptide or amide bond and be able to tell the difference. 4. Be able to recognize the three-letter abbreviations for the 20 amino acids! 5. Be able to name the structures of all 20 amino acids. Be able to say which contain R-groups that are nonpolar, polar, or charged! Be able to predict which R groups should be soluble in water and which should not. 6. Be able to recognize cysteine, cystine, a sulfhydryl group, and a disulfide bond. Which are more oxidized and which are more reduced? 7. Be able to recognize a salt bond (electrostatic interaction). 8. Given any two amino acids, predict whether their R-groups could form a salt bond at pH = 7.4. 9. What are the pKa's for the R-groups of aspartic acid, glutamic acid, histidine, lysine, and arginine? 10. Given the pH, predict whether the R-groups of the amino acids aspartic acid, glutamic acid, histidine, lysine, and arginine would be neutral or would carry a net negative or net positive charge. 11. Given the pH, predict whether the amino acids aspartic acid, glutamic acid, histidine, lysine, and arginine would be neutral or would carry a net negative or net positive charge. 12. Define the pI (the isoelectric point) for an amino acid. 13. Given any amino acid except cysteine serine, threonine and tyrosine, be able to predict the isoelectric point! 14. Is the substitution of a glutamate for a valine [valine for a glutamate] in sickle cell hemoglobin a conservative replacement? What about the substitution of an aspartate for a glutamate? 15. Given the written sequence for a protein, be able to identify the amino-terminus, the carboxyl-terminus, and the R-groups for each residue. 16. Concerning Michael Sichel: To the extent covered in this chapter, explain his disease in terms of amino acids. In the African American population, is the Sickle Cell allele a polymorphism. 17. Concerning Cal Kullis: To the extent covered in this chapter, explain his disease in terms of amino acids. 18. Concerning Di Abetes and in terms of amino acids, explain the difference between pork insulin, lispro, and synthetic human insulin. What are the possible advantages of each. 19. Concerning Ann Jeina, describe the isozymes of creatine kinase found in her body, their release following injury, and their use in diagnosing a myocardial infarction. Why do they react differently as antigens and why do they move differently in an electric field? 20. Understand the meaning of each of the keywords. Keywords: alanine, alpha-carboxyl, alpha-amino, alleles, amide bond, arginine, asparagine, aspartate, CK, MB-CK, conservative substitution, cysteine, cystine, cystinuria, disulfide bond, divergent evolution, electrostatic interactions, glutamate, glutamine, glycine, histidine, hydrophobic, isoelectric point, isoleucine, L-amino acids, leucine, lysine, lispro, methionine, net charge, oxidized, peptide bond. pI, phenylalanine, polymorphism, point mutation, proline, R-group, reduced, salt bond, serine, sickle cell anemia, sulfhydryl residue, threonine, tryptophane, tyrosine, valine. Assignments: Examine questions in chapter 6 Work questions 1-5 at the end of Chapter 6 Practice Questions for Chapter 6 Objectives Other Help Titration of Alanine with Hydroxide Titration of Lysine with Hydroxide Titration of Aspartate with Hydroxied Reference: Marks's Basic Medical Biochemistry: A Clinical Approach, 2nd Edition, 2004, Williams and Wilkins (ISBN: 0-7817-2145-8) by Colleen M. Smith PhD, Allan D. Marks MD, and Michael A. Lieberman PhD