706_S2006_Exam1key - Name: _KEY_ 7.06 Cell Biology EXAM #1...

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Name: _____________KEY__________________ 1 7.06 Cell Biology EXAM #1 KEY February 28, 2006 This is an OPEN BOOK exam, and you are allowed access to books, a calculator, and notes BUT NOT computers or any other types of electronic devices. Please write your answers in PEN (not pencil) to the questions in the space allotted. Please write only on the FRONT SIDE of each sheet, as we will Xerox all of the exams and thus only grade writing on the front. And be sure to put your NAME ON EACH PAGE in case they become separated! There are EIGHT pages including this cover sheet. Question 1. 23 pts __________ Question 2. 27 pts __________ Question 3. 21 pts __________ Question 4. 9 pts __________ Question 5. 20 pts __________ TOTAL 100 pts __________
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Name: _____________KEY__________________ 2 Question 1. (23 pts) You are studying transepithelial transport of glucose from the intestinal lumen to the extracellular medium surrounding the basal surface in cells that are growing in culture. You are using a system identical in set-up to that described for MDCK cells in the textbook, copied below: (a, 3 pts) If you performed immunofluorescence on permeabilized intestinal epithelial cells using an antibody against GLUT2, where would you find the fluorescent signal? You would see signal only in the basolateral surface of the membrane, as that is the only portion of the cell in which GLUT2 protein is found. GLUT2 is the uniporter that allows glucose to flow down its concentration gradient, from the inside of the cells to the blood. (b, 5 pts) If you performed the same experiment as above on intestinal epithelial cells that had been depleted of occludin and claudin, where would you see the fluorescent signal? Justify your answer. You would see the signal all over the plasma membrane (both the basolateral and apical sides), because these two proteins are essential for proper formation of tight junctions. One of the very important functions of tight junctions is to disallow proteins from diffusing freely between the basolateral and the apical sides of the membrane. (c, 8 pts) You are trying to design a new artificial transporter that would transport glucose from the intestinal lumen into intestinal epithelial cells. You have the ability to create novel transporters and target them to the apical membrane. You make the two new transporters listed below, and to test them you use recombinant DNA techniques learned in 7.02 and 7.03 to express these in the MDCK cells. For each new transporter below, state whether it could allow for movement of glucose across the apical membrane at all, and if yes, whether you think that glucose would move into or out of cells. (i) A 2 Ca 2+ /1 glucose symporter Yes, it would allow movement of glucose inside of the cell. Glucose is higher inside these cells than outside, and calcium is higher outside than inside. Thus the free energy
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Name: _____________KEY__________________ 3 released from moving calcium down its concentration gradient could be used to drive the
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This note was uploaded on 01/23/2012 for the course BIOLOGY lsm1301 taught by Professor Seow during the Spring '11 term at National University of Singapore.

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706_S2006_Exam1key - Name: _KEY_ 7.06 Cell Biology EXAM #1...

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