old exam 1

old exam 1 - Imagine a cell in which the membrane is...

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Imagine a cell in which the membrane is impermeable to Na + and Cl - , freely permeable to H 2 O, and moderately permeable to urea. The cell is happily floating in an isoosmotic solution of NaCl. Which one of the following would happen if you abruptly added urea to the solution bathing the cell? a. The cell would swell and remain swollen. b. The cell would shrink and remain shrunken. c. The cell would swell, but after a brief period of time, it would return to its original volume. d. The cell would shrink, but after a brief period of time, it would return to its original volume. e. Adding urea would have no effect on the cell’s volume, not even briefly. Which one of the following proteins in the membrane of the intestinal epithelial cell is most directly involved in the success of oral rehydration therapy as it is currently practiced in cases of bacterial gastroenteritis involving severe diarrhea? a. Na+/K+ ATPase b. CFTR Cl- channel c. Na+-glucose symport d. aquaporin e. epithelial Na+ channel Refer to attached diagram. This diagram shows a typical sweat (eccrine) gland in human skin. The secretory coil produces a salty secretion that is mostly isotonic with the blood plasma. As this fluid passes through the reabsorptive duct, NaCl is reabsorbed into the blood, such that sweat secreted onto the skin surface is hypotonic. Assume that along its entire length, the walls of the sweat gland consist of a single layer of epithelial cells joined by tight junctions. Which one of the following statements about this system is false? a. Reabsorptive epithelial cells are impermeable to H2O. b. Na+/K+ pumps are located in the apical membranes of reabsorptive epithelial cells. c. CFTR Cl- channels are located in the apical membranes of secretory epithelial cells. d. Epithelial Na+ channels are located in the apical membranes of reabsorptive epithelial cells. e. Patients with cystic fibrosis would be expected to have abnormally high levels of NaCl in their secreted sweat. Some epithelial cells are treated with a drug that blocks Cl- ion channels, and in response, the cells depolarize slightly. Which one of the following is a correct conclusion about the normal state of these cells, before the drug was applied? a. Cl- ions are actively transported out of the cells. b. Cl- ions are actively transported into the cells. c. The cells do not actively transport Cl- ions. d. Insufficient information is given to determine if and how Cl- ions are transported. Supplements of the steroid hormone estrogen can be taken via several different routes, for
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This note was uploaded on 02/28/2011 for the course BISC 307 taught by Professor Herrera during the Spring '08 term at USC.

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old exam 1 - Imagine a cell in which the membrane is...

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