Exam 2 - Cell Biology / Cell Biochemistry BIOL 4374 / BCHS...

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Cell Biology / Cell Biochemistry BIOL 4374 / BCHS 4313 Exam 2 Mar 9, 2009 Read each question carefully . Chose the single best answer to each of the following questions. In some cases, key words are emphasized in bold italics font. 1. The relationship between the equilibrium potential for an ion, and the concentration gradient of that ion across a semi-permeable membrane is described in … a. the Nernst equation b. page 634 of the textbook c. the phone book d. the Houston Chronicle e. none of the above 2. The equilibrium potential of a “typical” excitable membrane is approximately -70 mV. This value is closest to the equilibrium potential for which ion? a. potassium b. sodium c. chloride d. calcium e. lithium 3. The membrane potential of an excitable membrane is primarily determined by which of the following proteins? a. sodium-potassium ATPase b. voltage gated sodium channels c. passive potassium channels d. ABC pump e. Ran GTPase 4. Which structural domain is responsible for inactivation of the voltage gated potassium channel? a. C-terminal helical domain b. N-terminal globular domain c. P segment d. S4 transmembrane helix e. none of the above 5. Which of the following structural features of the aquaporin channel prevents the transport of hydrogen ions? a. appropriately spaced carbonyl oxygen atoms along the selectivity channel b. a string of negatively charged amino acids near the extracellular opening of the channel c. a string of positively charged amino acids near the cytosolic opening of the channel d. two consecutive asparagine residues near the middle of the channel e. none of these, because hydrogen ions freely pass through the aquaporin channel 6. What is the basis for ion selectivity in the voltage gated potassium channel? a. appropriately spaced carbonyl oxygen atoms along the selectivity channel b. a cluster of negatively charged amino acids along the selectivity channel c. a cluster of positively charged amino acids along the selectivity channel d. two consecutive asparagine residues near the middle of the channel e. none of these, because ion selectivity is determined by the concentration gradient 7. Which of the following events is responsible for the depolarizing phase of the action potential? a. opening of voltage gated sodium channels b. opening of voltage gated potassium channels c. closing of voltage gated sodium channels d. closing of voltage gated potassium channels e. inactivation of voltage gated sodium channels
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8. The changes in ion permeability of the axonal membrane that give rise to the action potential were first determined using which model organism? a. mouse b. fly c. squid d. horseshoe crab e. cougar 9. Action potentials propagate faster along myelinated axons because … a. myelin is an excellent electrical insulator b. voltage gated sodium channels are concentrated at the nodes c. action potentials “jump” from node to node d. all of the above e. none of the above
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This note was uploaded on 10/05/2010 for the course BCHS 3305 taught by Professor Briggs during the Spring '10 term at University of Houston-Victoria.

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Exam 2 - Cell Biology / Cell Biochemistry BIOL 4374 / BCHS...

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