Biochem: Chapter 4 Quiz Questions

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Biochem: Chapter 4 Quiz Questions
2014-01-22 23:51:35
Chem 436A Shamansky Chapter

Ch. 4 Quiz Questions
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  1. What is the net overall charge on glutamic acid at pH 12.
  2. Arginine Contains what kind of group?
    Guanidino Group
  3. What would be the net charge for the peptide below at pH 7.0?Asn-Asp-Cys-Tyr-Ser-Val-Lys
  4. Why is Gly considered achiral?
    Because Gly's side chain is an H
  5. Which amino acids cannot form H-bonds?
    • the amino acids with nonpolar side chains.
    • (exception is tryptophan which has an H it can donate )
  6. What is the net charge at pH 7.0 on a peptide with the sequence?Ala-Thr-Leu-Asp-Ala-Lys-Pro-Glu
  7. Histidine contains what kind of group?
    imidazole group
  8. Which amino acid(s) could be used to make a buffer at pH 4.0?
    CORRECT. In order to make a buffer from an amino acid an ionizable side chain is required, and to make a buffer at pH 4.0 the pKa of that side chain should be approximately 4. Both Asp and Glu meet this requirement.
  9. What is the net charge on the amino acid lysine at pH 7.
    • +1
    • 1. At pH 7 lysine's  carbon carboxyl will have a -1 charge, its  carbon amino group will have a +1 charge and its side chain amino group will have a +1 charge, giving it an overall charge of -1 +1 +1 = +1
    • Val-Ser-Ile-Glu-Lys