CHEM153A_midterm1_W09_answers

CHEM153A_midterm1_W09_answers - Chem 153A, Winter 2009...

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Chem 153A, Winter 2009 Midterm Exam 1 Answers 1/2 Midterm 1 Answer Key Part I. Multiple Choice. 1. B. 2. D. 3. A. 4. C. 5. E. This is incorrect because glycerophospho- lipids do not form micelles. Part II. True or False? 6. False ; a protein’s entropy decreases as it folds. Water entropy increases. 7. True 8. True 9. False ; although unsaturated fatty acids are individually less flexible, due to their double bonds, the kinked chains force a looser packing and greater membrane flexibility. 10. False ; although water prefers to form H-bonds, it can pack against other compounds to form van der Waals interactions. 11. True Part III. Short answer. 12. a. Trp has a carboxyl group b. The B of the carboxyl group lowers the pKa of the tryptophan amino group. The E of the carboxyl group raises the pKa of the tryptophan amino group. c. somewhat higher (D) 13. B, J, O, U, X, Z 14. a. Having hydrophobic and hydrophilic parts b. Both 1 & 2 c. Yes (because the sequences are similar) 15. The longer, saturated fatty acids, which have higher melting points, will help stiffen the membrane. This is desirable in thermophilic bacteria, where the high temperature makes the membrane more
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CHEM153A_midterm1_W09_answers - Chem 153A, Winter 2009...

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