SolutionProblemSetC

SolutionProblemSetC - Problem Set C Lectures 7, 8 and 9 Ch....

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Lectures 7, 8 and 9 Ch. 7 and 8 1. Membrane Fluidity a. You are a graduate student doing research of cell membranes at UCSD. When decreasing the temperature of cells 1 and 2, you notice that the plasma membrane of cell 1 solidifies at a significantly lower temperature than cell 2. Explain the main reason for this observation in 1-2 sentences. Key Concept: unsaturated fatty acid tail content in phospholipids bi-layers Answer: Cell 1 must have a larger amount of unsaturated fatty acid tails in the hydrophobic region of the lipid bi-layer. The “kinks” formed by the double bonds in the hydrocarbon tails of the unsaturated FA reduces the ability of the phospholipids to settle into a closely packed arrangement and solidify. b. Cholesterol is sometimes thought of as a “temperature buffer” for plasma membranes. Thus, at high temperatures, cholesterol (increases / decreases ) membrane fluidity and at low temperatures, cholesterol ( increases / decreases) membrane fluidity. Key Concept: Phospholipid packing. The cholesterol adds rigidity to the membrane at high temperatures and it hinders close packing at lower temperatures like the unsaturated FA tails. c. __ Lateral __ movement of phospholipids occurs about 10 7 times/second. d. Phospholipids _ flip-flop _ across the plasma membrane about 1 time/month. 2. Endomembrane System Correctly order the path of a secretory protein from synthesis to secretion. (Answers may be used more that once) I. Plasma Membrane II. Trans-Golgi III. ER lumen IV. Cis-Golgi V. Vesicle Answer: III, V, IV, II, V, I 3. Transport a. Complete the chart. Transport System Passive/Active (Is ATP used?) Up/ Down Concentration Gradient Transport Protein Used Particles Transported Diffusion Passive, no ATP used Down None Small Hydrophobic Facilitated Diffusion Passive, no ATP used Down Channel/Carrier Protein Ex) Aquaporin
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SolutionProblemSetC - Problem Set C Lectures 7, 8 and 9 Ch....

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