Unit3_Review_questions

Unit3_Review_questions - Membrane review questions 1 Rank...

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Membrane review questions 1. Rank the following molecules according to the ease with which they can cross a phospholipid bilayer: glucose, water, phosphate, chloride ion, oxygen gas, the amino acid proline 2. Explain the rationale you used in ranking the molecules in question #1. 3. The cell membrane is often described as “selectively-permeable.” What is meant by this term? 4. Cells can change the composition of their membranes to adapt to different environmental conditions. What component of the membrane could be changed to help an organism tolerate cold? Heat? Be specific as to the exact component, and how it could be changed. 5. What is the difference between diffusion and osmosis? 6. Use the chart below to describe what happens to a cell that has a cell wall, and a cell that lacks one, when placed in these different environments. Hypertonic Hypotonic Isotonic No cell wall Cell wall 7. Ethanol, the active molecule in alcoholic beverages, is a small, polar, uncharged molecule. Would you predict that this molecule crosses membranes by diffusion slowly or quickly? Explain your reasoning. 8. Bags of dialysis tubing, a selectively permeable membrane, are filled with glucose solutions at various concentrations. Each bag is then placed in an identical beaker containing an identical volume of a particular glucose solution. The tubing is impermeable to glucose. a. If a bag contained solute in the same concentration as the solution in the beaker, how would its mass change through time? How would you describe this bag relative to its environment (hypotonic, hypertonic, isotonic)? b. If a bag contained solute in a much higher concentration than the solution in the beaker, how would its mass change through time? How would you describe this bag relative to its environment (hypotonic, hypertonic, isotonic)? c. If a bag contained solute in a much lower concentration than the solution in the beaker, how would its mass change through time? How would you describe this bag relative to its environment (hypotonic, hypertonic, isotonic)?
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d. A bag gains mass for the first half of the experiment, but after that its mass is stable. At the start of the experiment, the bag is (circle one) hypertonic / hypotonic / isotonic to its environment. But by the end of the experiment, the bag is no longer gaining mass because it is (circle one) hypertonic / hypotonic / isotonic to its environment. e. Would the mass changes of the bags be different if the solute outside the bags was made using sodium ions (at the same molarity as the glucose solution used above; assume the dialysis tubing is impermeable to sodium ions)? Why or why not? 9. Glucose (a monosaccharide) and sucrose (a disaccharide) are placed in a U-shaped tube at the concentrations shown in the figure. The membrane is not permeable to either sugar. In which direction will there be net movement of water? (MW = molecular weight g/mol). (HINT: The direction of water movement during osmosis is determined by the molar concentration of solute molecules on each side of the
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Unit3_Review_questions - Membrane review questions 1 Rank...

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