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UD CHEM 342 - CHEM 342 Final Exam

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CHEM-342 Introduction to Biochemistry Final Examination - Individual (Part I) Tuesday, 27 May 2008 7:00 – 8:45 PM H. B. White - Instructor Your Name____________________________ We are not afraid to follow truth where ever it may lead, nor tolerate error so long as reason is left free to combat it. Thomas JeffersonClass average 61.9, Class range 32-84/90, N=26 Important - Please read this before you turn the page. $ For the first hour, this is a closed book examination. From 8 – 8:45 PM you may refer to your course notes and materials. $ This examination will assess your learning, problem-solving skills, and ability to communicate clearly. It is intended to be challenging even to the best students in the class. Writing reflects how you think. Among the “right answers” I will read, some will be better than others because they show greater depth of understanding, avoid extraneous or inaccurate information, provide a more logical structure, use appropriate examples, and choose words with precision. Better quality answers will receive higher marks. Therefore organize your thoughts before you write or draw. Strive to write not that you may be understood, but rather that you cannot possibly be misunderstood. Stream of consciousness answers are rarely well organized or clearly presented. $ This examination emphasizes work done in this course since Spring Break; however, knowledge is not so conveniently compartmentalized. Therefore, you should feel free to use any relevant example from your experience, if it is appropriate. $ There are 8 pages to this part of the examination (counting this cover page and the information sheet at the back). Please write your name on each page. Feel free to use the backs of pages, if you need more space. $ Part I (90 points) This individual part of the examination, includes 10 problems and short essay questions. $ Part II (30 points) The group part of the examination will require you to deal with new information collaboratively. $ If you complete Part I early, you may leave the room and move to 205 Brown Lab where the Group Part of the examination will begin about 9 PM. $ You may refer to your notes, course reader, handouts, or graded homework assignments after the first hour of the examination. $ Attempt to draw a picture or diagram as part of your answer to every question. $ Graded examinations may be picked up Thursday morning, 29 May. $ Have a productive and safe summer.CHEM-342 Introduction to Biochemistry Your Name ____________________________________ Final Examination Individual Part, 27 May 2008 Page 2 Short Answer: (3 points each, 27 points total): The following require brief but well-worded answers that concisely and accurately answer the question in one or two sentences. 1. Linus Pauling hypothesized that sickle cell anemia was a disease of the hemoglobin molecule and not of the red blood cell several years before he and his coworkers produced molecular evidence to test and support his hypothesis. A. Specifically, what led Pauling to deduce that hemoglobin in sickled cells was different? B. What experimental evidence did Pauling et al. (1949) provide to support the hypothesis? 2. Building on Pauling’s work, Vernon Ingram set about to identify the exact chemical difference between normal human hemoglobin and sickle cell hemoglobin. His strategy was to make a complex problem simpler. A. Conceptually, what did Ingram do to simplify the problem? B. What difference did Ingram find? 3. Howard Dintzis, having worked with Ingram in the same laboratory in Cambridge, England, later used Ingram’s methods to solve a fundamental problem in biochemistry. A. What problem did Dintzis solve? B. What did Dintzis conclude? 4. Intrigued by the high frequency of the sickle cell gene in parts of Africa, Anthony Allison hypothesized that natural selection must be involved. A. By what logic did Allison deduce that natural selection affected the frequency of the sickle cell gene? B. What experimental evidence did Allison provide in support of his hypothesis?CHEM-342 Introduction to Biochemistry Your Name ____________________________________ Final Examination Individual Part, 27 May 2008 Page 3 5. Howard Dintzis was not the first biochemist to study hemoglobin synthesis with isotopically labeled amino acids. Fifteen years earlier, David Shemin and David Rittenberg used 15N glycine as a precursor and discovered something quite unexpected. A. What did Shemin and Rittenberg discover that was unexpected? 6. (12 Points) If David Shemin had decided to feed rabbits uniformly-labeled 15N-glycine, his result would have been qualitatively similar to the results he got on himself shown below. A. (6 points) Imagine an experiment like Shemin’s in which rabbits (instead of humans) were fed 14C-glycine (instead of 15N-glycine). Draw a figure above depicting the amount of 14C in hemin and in hemoglobin as a function of time. B. (6 points) Imagine an experiment like Shemin’s in which rabbits (instead of humans) were fed 14C-leucine (instead of 14C-glycine). Draw a figure below depicting the amount of 14C in hemin and in hemoglobin as a function of time. (You may make comments to explain your reasoning.)CHEM-342 Introduction to Biochemistry Your Name ____________________________________ Final Examination Individual Part, 27 May 2008 Page 4 7. (21 Points) Food scientists have an interest in food flavor. Frequently, the breakdown of proteins generates bitter-tasting peptides. Because hemoglobin is an abundant protein in blood, significant amounts of it remain in meat products and could affect taste. Pepsin hydrolysis of beef hemoglobin yields several bitter peptides. Among them is a fragment of the β-globin chain including amino acid residues 32 through 40 shown below. Its bitterness at 250 μM is equivalent to 73 μM quinine, a very bitter compound. [Auloes-Dufau et al. (1995) “Bitter peptide from hemoglobin hydrolysate: Isolation and characterization.” FEBS Lett. 364, 115-119.] V-V-Y-P-W-T-Q-R-F A. (5 points) If one were separating pepsin peptides of bovine hemoglobin by ion exchange column chromatography and monitoring the peptides by their UV absorption, would you expect this peptide to absorb strongly or weakly at 280 nm? Explain your answer. B. (5 Points) After studying many peptides


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UD CHEM 342 - CHEM 342 Final Exam

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