2009 Exam 3 - NAME_KEY MIDTERM EXAM III BIOLOGY 231 10 November 2009 GENERAL INSTRUCTIONS 1 Answer all questions IN INK and do not use white-out if

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NAME: _________ KEY _________________ MIDTERM EXAM III BIOLOGY 231 10 November 2009 ________________________________________________________________________________ -1- GENERAL INSTRUCTIONS: 1. Answer all questions IN INK, and do not use white-out if you anticipate requesting a re-grade. 2. No calculators. 3. Confine each answer to the BOX or SPACE provided. Only what is clearly written in the box or space will be graded! Use the back of the pages for “rough drafts” if you like. 4. SHOW YOUR WORK. SHOW ALL CALCULATIONS. 5. Make sure that your name is PRINTED LEGIBLY on EACH PAGE. 6. This exam consists of 10 problems on 11 pages and it is worth a total of 100 points. Information that might be useful: ! Use this convention for numbering the residues of a protein: label the first (most N-terminal) residue of the mature protein as “1", then number residues consecutively to the C-terminus. If an N-terminal signal sequence is removed during synthesis, re-number the residues starting with the new N-terminus = 1. ! A hydrophobic signal sequence can be a start-transfer or stop-transfer sequence depending on its position in the polypeptide. ! “Codon number” refers to how many codons away from the AUG you are in an mRNA (with the first AUG = #1). “Residue number” refers to how many amino acid residues away from the N–terminus you are in a protein (with the N–terminal aa = #1). ! An oligomer is a very small polymer, formed by the assembly of a small number of monomeric subunits. ! On this day, 10 November, in 1975, the iron ore freighter SS Edmund Fitzgerald sank in a storm on Lake Superior, killing all 29 crew members. It was the worst accident in Lake Superior’s history, and was immortalized by Canadian folk singer Gordon Lightfoot’s "The Wreck of the Edmund Fitzgerald."
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NAME: _________ KEY _________________ MIDTERM EXAM III BIOLOGY 231 10 November 2009 ________________________________________________________________________________ -2- (1) You have identified an mRNA for a plasma membrane protein, “Nerf Protein,” and have sequenced it, as shown schematically below. You have determined that there are 3 separate stretches of amino acids hydrophobic enough to be signal sequences – they are shown by the white boxes on the sequence. Codon numbers are also shown. You carry out an in vitro translation of this mRNA. (a) 6 pts. On the membrane schematic below, draw the Nerf Protein as it would be arranged in the membrane of a microsome after in vitro translation. LABEL the N and C termini, LABEL the amino acid residue numbers at the N terminus, C terminus, and at EACH BOUNDARY between a membrane-span and a cytoplasmic or lumenal part of the protein. If the protein is processed after translation, renumber the residues so that the N-terminus = residue 1.
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NAME: _________ KEY _________________ MIDTERM EXAM III BIOLOGY 231 10 November 2009 ________________________________________________________________________________ -3- (b) 4 pts. After expressing the protein in cultured cells, you add a protease to the culture medium and allow it to digest the extracellular portions of your protein. Then you recover the remaining fragments of the protein from the plasma membrane, separate them on an SDS polyacrylamide gel, and stain them. Which of the patterns below would you obtain? Assume that one residue = 0.1 kD in MW. WRITE the correct lane number (choices are 1-5) in the box at left.
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This note was uploaded on 03/12/2012 for the course BIO 231 taught by Professor Hollenbeck during the Fall '11 term at Purdue University-West Lafayette.

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2009 Exam 3 - NAME_KEY MIDTERM EXAM III BIOLOGY 231 10 November 2009 GENERAL INSTRUCTIONS 1 Answer all questions IN INK and do not use white-out if

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