exam-answers_2001 - MCB110 FINAL May 14, 2001 . Your name...

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MCB110 FINAL May 14, 2001 . Your name and student ID QUESTION POINTS 1 (15 points) 2 (15 points) 3 (15 points) 4 (10 points) 5 (10 points) 6 (25 points) 7 (15 points) 8 (10 points) 9 (15 points) 10 (10 points) 11 (15 points) 12 (20 points) 13 (10 points) 14 (5 points) 15 (50 points) 16 (50 points) TOTAL (300 points) WARNING: Your exam will be taken apart and each question graded separately. Therefore, if you do not put your name and ID# on every page or if you write an answer for one question on the backside of a page for a different question you are in danger of irreversibly LOSING POINTS!
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QUESTION 1 - (a) You are growing bacteria at room temperature and at 4 C. What type of differences ˚ would you expect in the lipid composition of the two colonies? (5) At 4 C lipids will have shorter chains and more unsaturated bonds ˚ (b) - Which will have a higher rate of spontaneous flip-flop, phosphatidic acid or phosphatidyl serine and why? (5) Phosphatidic acid as the polar head is smaller and less charged, and thus less energetically unfavorable to pass through the hydrophobic bilayer. (c) - Can you think of a reason why phosphatidyl inositol is more abundant in the inner leaflet of the plasma membrane? (5) Because of the involvement of PI phosphate derivatives in signal transduction QUESTION 2 - You have cloned a new integral membrane protein from erythrocyte plasma membrane. Analysis of the sequence has given you the following hydropathy plot. Mass spectroscopy of the purified protein indicates than residues near the C-terminus are glycosylated. Can you draw a diagram of the most likely secondary structure of this protein and its orientation in the membrane with respect to the outside/ cytosol? (5) - How can you visually determine if this protein is attached to focal adhesions. Tip you have available antibodies against the C-terminus of the protein. You should know two possible answers . (10) Attachment to focal adhesions (FA) will restrict the movement of the protein in the membrane. One could use FRAP or video microscopy with gold-labeled antibodies to test the mobility of the protein. (enough for 10 points) Alternatively, if you have a marker for FA (such as an antibody for phosphotyrosine residues) you can look at colocalization by fluorescence microscopy
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QUESTION 3 - What are the differences in the mode of action of the glucose facilitative transporter and the Na+/glucose cotransporter? (5) The glucose transporter transports glucose down a concentration gradient. The glucose/Na transporter moves glucose against a concentration gradient by coupling it to the movement of Na down a concentration gradient. - What energy-consuming process is ultimately required for the functioning of the cotransporter? (5)
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exam-answers_2001 - MCB110 FINAL May 14, 2001 . Your name...

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