Fall 2006 - Prelim 1 - BioBM 330 Name _ 1st Prelim Cornell...

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BioBM 330 Name ____________________________ 1st Prelim Cornell ID#________________________ 28 September, 2006 Please do not lift this sheet until the signal is given! Please be certain that your exam contains a total of 10 pages! Please write your name on EACH page. We urge you not to get bogged down on any one question. If you do not see the point fairly quickly, go on to the other questions and come back if time permits. You may have two hours for the whole exam. 1. _________ (8) 10. _________ (7) 2. _________ (2) 11. _________ (8) 3. _________ (2) 12. _________ (2) 4. _________ (2) 13. _________ (6) 5. _________ (8) 14. _________ (6) 6. _________ (3) 15. _________ (11) 7. _________ (4) 16. _________ (3) 8. _________ (3) 17. _________ (6) 9. _________ (8) 18. _________ (7) 19. _________ (9) Total _________________(105) pK values (25°C) α -COOH group 2.0 α -NH 3 + group 9.0 Aspartic acid side chain 3.9 Glutamic acid side chain 4.3 Histidine side chain 6.0 Cysteine side chain 8.3 Tyrosine side chain 10.9 Lysine side chain 10.8 Arginine side chain 12.5
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Name: ___________________________ 2 1. a. (6 points) Draw the structures of leucine and isoleucine at pH 7.0. leucine isoleucine b. (2 points) Poly-L-leucine in an organic solvent such as dioxane is a helical, whereas poly-L-isoleucine is not. Why do these amino acids have different helix-forming tendencies? 2. (2 points) A mutation that changes an alanine residue in the interior of a protein to a valine is found to lead to a loss of activity. However, activity is regained when a second mutation at a different position changes an isoleucine residue to glycine. How might this second mutation lead to a restoration of activity? 3. (2 points) Histones are proteins of eukaryotic cell nuclei. They are tightly bound to DNA, which has many phosphate groups. The pI of histones is very high, about 10.8. Considering these two facts, what amino acids must be present in relatively large numbers in histones? 4. (2 points) In the course of purifying an enzyme, a researcher performs a purification step that results in an increase in the total activity to a value greater than that present in the original crude extract. Explain how the amount of total activity might increase?
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Fall 2006 - Prelim 1 - BioBM 330 Name _ 1st Prelim Cornell...

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