test3 - Biol 302 April 17, 2007 Exam 3 Version 1 Answer Key...

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Biol 302 April 17, 2007 Exam 3 Version 1 Answer Key Name ________________________________ SSN ___________ 1. Which of the following lists the general steps of a signaling pathway in the correct order? 1. a receptor generates a new signal 2. cellular response (changes in gene expression) 3. a target protein such as a gene regulatory proteins is activated 4. an extracellular signal is bound by a receptor 5. a message is passed from one signaling molecule to the next a. 3, 2, 5, 1, 4 b. 1, 4, 5, 3, 2 c. 3, 5, 1, 2, 4 d. 4, 1, 5, 3, 2 e. 4, 5, 1, 2, 3 2. True or false. Upon signaling binding, a G-protein-linked receptor can activate many G proteins. a. true b. false 3. Fill in the blank in the following signaling pathway. extracellular signal receptor tyrosine kinase _______ MAP kinase cascade a. Ras b. G protein c. cAMP d. adenylyl cyclase e. Ca 2+ 4. In _____________signaling, extracellular signals act in the local environment while in _______________ signaling, extracellular signals are broadcast throughout the body. a. neuronal, panacrine b. panacrine, endocrine c. endocrine, neuronal d. endocrine, panacrine e. none of the above 5. When a trimeric G protein is activated by a cell-surface receptor a. the β subunit exchanges its bound GDP for GTP. b. the GDP bound to the α subunit is phosphorylated to form bound GTP. c. it dissociates into a free subunit and an αγ subunit. d. the subunit exchanges its bound GDP for GTP. e. it dissociates into an active subunit and an inactive βγ subunit. 1
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6. All members of the steroid hormone receptor family a. are cell-surface receptors. b. do not undergo conformational change. c. are found only in the cytoplasm. d. interact with signal molecules that diffuse through the plasma membrane. e. all of the above 7. The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by a. way of a G-protein-mediated mechanism. b. way of a receptor tyrosine kinase. c. diffusing into cells and stimulating the cyclase directly. d. way of a cell-surface receptor linked to an intracellular signaling pathway. e. activation of intracellular protein kinases. 8. Which of the following statements is true ? a. most signal molecules bind to cell-surface receptors b. all cells can only respond to a single signal c. all cell only produce a single type of receptor d. all cells have a common response upon perception of a particular signal e. none of the above 9. Which of the following molecules acts as a molecular switch whose activity is regulated by whether it is bound to GTP or GDP? a. cAMP b. Ras c. receptor tyrosine kinase d. MAP kinase e. DAG (diacylglycerol) 10. Which of the following statements concerning receptor tyrosine kinases is false ? a. they are a type of enzyme-linked receptors
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test3 - Biol 302 April 17, 2007 Exam 3 Version 1 Answer Key...

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