Exam 1 Posted Answers

Exam 1 Posted Answers - BISC 307 Spring 2009 Exam 1 Answers...

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BISC 307 – Spring 2009 Exam 1 Answers 1 Posted Answers.doc Page 1 of 6 3 pts. 4 pts. 3 pts. 4 pts. 6 pts. 1. Breathing raises the concentration of O 2 in the blood, lowers the concentration of CO 2 in the blood, and raises blood pH. According to the principles of negative feedback regulation, which one of the following is most likely to stimulate an increase in breathing? (d) a. an increase in blood O 2 concentration b. a decrease in blood CO 2 concentration c. an increase in blood pH d. none of the above would stimulate an increase in breathing 2. In a typical mammalian cell, which one of the following is most likely to occur if the Na + /K + ATPase is inhibited with ouabain? (c) a. a decrease in intracellular [Na + ] b. an increase in intracellular [K + ] c. an increase in intracellular [Ca 2+ ] d. an increase in Na + -glucose co-transport e. an increase in Na + -Ca 2+ exchange 3. Which one of the following statements is false? (d) a. A slice of potato immersed in a hypotonic aqueous solution is likely to swell. b. Sodium-dependent glucose transport is an example of secondary active transport. c. The glucose transporter can move glucose in either direction across the plasma membrane. d. The symptoms of cystic fibrosis are consequences of a defect in the epithelial Na + channel. e. Epithelial cells involved in the transport of water from one body compartment to another are likely to express aquaporin molecules. 4. Imagine two aqueous solutions, A and B, that are separated by a membrane that is permeable to K + but not to Cl - or H 2 O. Solution A is 100 mM KCl, and solution B is 1 mM KCl. Which one of the following statements is most likely to be true? (e) a. Solution B is hyperosmotic compared to solution A. b. K + ions will diffuse from solution A to solution B until the [K + ] of both solutions is 50.5 mM. c. K + ions will diffuse from solution B to solution A until the [K + ] of both solutions is 50.5 mM. d. Over time, osmosis will increase the volume of solution A and decrease the volume of solution B. e. Solution A is electrically negative with respect to solution B. 5. The effects of hormones on target cells can be tremendously amplified by intracellular signaling pathways. In the case of the cAMP signaling pathway, which steps are responsible for this amplification? ANS: Amplification occurs at several steps. Binding of one hormone to its receptor can activate several stimulatory G-proteins. Each of these can activate several adenylyl cyclase enzymes, each of which generates many molecules of cAMP. These cAMP molecules in turn activate many protein kinase A molecules, each of which can phosphorylate many target proteins. Some of the target proteins may be enzymes, whose stimulated (or inhibited) activity further amplifies Exam
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6. When the neurotransmitter GABA binds to its postsynaptic receptors, the Cl - permeability of the postsynaptic membrane increases. In the adult mouse brain, this causes hyperpolarizing IPSPs. In young postnatal mice, however, GABA causes depolarizing EPSPs.
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Exam 1 Posted Answers - BISC 307 Spring 2009 Exam 1 Answers...

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