Exam 1 key - Bio 221 Fall 2010 Name_KEY_ Exam 1 [TEAR OFF...

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Bio 221 Fall 2010 Name______________ KEY __________________ Exam 1 [TEAR OFF THE FIRST PAGE OF THE EXAM AND HAND IT IN WITH THE SCANTRON.] Short Answer. 25 points (5 points each). 1. What is the difference between strong bonds and weak bonds ? Provide one example of a strong bond and two examples of weak bonds that are involved in protein tertiary structure. State the names of a few amino acids that could be involved in each type of bond you mentioned. Difference between strong and weak: Strong bonds involve electron sharing. Weak bonds involve charge interactions. Strong bonds need enzymes to make and break them. Weak bonds do not. (+2) (+0.5 each) STRONG WEAK WEAK Example: disulfide van der Waals hydrogen ionic Amino acid names: cysteine any hydro- ser, thr, asn, a + chg phobic aa gln, tyr, trp, with arg, his a - chg 2. For each of the following structures, name which macromolecule is represented, and give the name of the circled bond. (+0.5 each) E D C B A A B C D E macromolecule: nucleic acid protein carbohydrate lipid carbohydrate bond: phosphodiester peptide α -glycosidic ester or β -glycosidic (tri)glyceride
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3. Sketch a representation of a Gram negative and of a Gram positive bacterial cell envelope. Label where appropriate: Peptidoglycan , LPS , Periplasm . GRAM NEG GRAM POS (+2 for drawings, +1 for each correct label) 4. Show (diagram) how a Type III secretory system is located in the bacterial cell envelope. Explain why study of Type III secretory systems is of Medical interest. Peptidoglycan Periplasm LPS T3SS are of medical interest because: - frequently present in pathogens - efficient secretion of toxins directly into target cell - intermediate in the evolution of flagella (+1 for needle complex, +1 for bushings, +1 for going through both bacterial membranes, +2 for reason for interest) 5. Draw a bacterial growth curve. (+1) Label the x- and y-axes. (+1) Label the phases of the growth curve. (+2) Draw an arrow pointing to the phase of the curve in which the number of dividing cells is equal to the number of dying cells. (+1) stationary decline / death exponential (log) lag log (or ln) cell number (or OD) time
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3 Multiple choice. 75 points (1.5 points each). 1. Why did early attempts to repeat Louis Pasteur's pasteurization experiments fail? A. Pasteur's technique was complicated and difficult to master. B. Others did not use the same swan-necked flasks that Pasteur did. (+0.5: P. did use these, but so did others) C. In 1870 scientists were unaware of any life forms that could survive in boiling water. D. Others omitted a significant step that Pasteur included in his experiment. E. Because it was an industry secret, Pasteur did not publish his methods. 2.
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This note was uploaded on 01/17/2011 for the course BIOLOGY 221 taught by Professor Walter during the Fall '10 term at Purdue University-West Lafayette.

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Exam 1 key - Bio 221 Fall 2010 Name_KEY_ Exam 1 [TEAR OFF...

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