bisc307--exam_1_spring_06 - Exam 1 Answers BISC 307L...

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Exam 1 Answers BISC 307L – General Physiology February 6, 2006 NOTE: The given answers for the subjective questions are not the only ones possible. Grading for each of the subjective questions is done relative to other students’ answers, by one TA who applied uniform criteria. 1. Identify an example of a positive feedback cycle that occurs somewhere in the body, and briefly describe the important features of this cycle. ANS: Several are possible, e.g., parturition, defecation, Hodgkin cycle, etc. Complete answers should explain the initial stimulus, the initial response, the effects of that response, how those effects reinforce the initial response, etc., and how the cycle brings about a change in state of the system. Contrasts with negative feedback regulatory cycles could strengthen the answer. 2. At the start of an experiment, a 1 M aqueous solution of CaCl 2 is separated from an equal volume of a 1 M aqueous solution of KCl by a membrane that is permeable to water but not to any ions. After a while, would you expect the volume of the CaCl 2 solution (the left side) to … (a) a. Increase. 1 M KCl 1 M CaCl 2 b. Decrease. c. Decrease to zero. d. Stay the same. 3. Which one of the following statements is false? (c) a. The glucose transporter can move glucose in either direction across the plasma membrane. b. Epithelial cells involved in the transport of water from one body compartment to another are likely to express aquaporin molecules. c. Sodium-dependent glucose transport is an example of primary active transport. d. The symptoms of cystic fibrosis are consequences of a defective Cl - channel. e. A slice of potato immersed in a hypotonic aqueous solution is likely to swell. 4. Briefly explain why G-proteins have an endogenous GTPase activity. ANS: G-proteins are activated by binding molecules of GTP. The endogenous GTPase activity hydrolyzes this bound GTP, inactivating the G-protein and thus terminating the signaling mechanism. 5. In which parts of the cell are receptors for estrogen and testosterone located? ANS: In the cytoplasm (ICF) or in the nucleus. Either would be OK for full credit. 6. Which one of the following correctly describes a function of gap junctions between adjacent cells? (e) a. They cause adjacent cells to adhere strongly to each other.
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b. They form a diffusion barrier, so extracellular solutes cannot leak between cells. c. They allow G-proteins to diffuse between cells.
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This note was uploaded on 05/03/2010 for the course BISC 307L taught by Professor Herrera during the Spring '08 term at USC.

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bisc307--exam_1_spring_06 - Exam 1 Answers BISC 307L...

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