Exam2 - Cell Biology / Cell Biochemistry BIOL 4374 / BCHS...

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Cell Biology / Cell Biochemistry BIOL 4374 / BCHS 4313 Exam 2 Oct 5, 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 resting 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 2. The resting membrane potential of a neuron is primarily determined by which of the following proteins? a. potassium leak channels b. voltage gated sodium channels c. voltage gated potassium channels d. sodium-potassium ATPase e. Ran GTPase 3. Which structural domain is responsible for ion selectivity 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 4. 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 5. 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 6. 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 7. Which of the following is false about the nicotinic acetylcholine receptor? a. it is a heteropentameric, ligand gated ion channel b. acetylcholine molecules bind to both of the α subunits c. the channel is permeable to sodium ions d. it was the first ligand gated ion channel to be isolated e. all of the above are true
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8. 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 9. You have identified a novel transport system for the uptake of tryptophan into yeast. You show that, as the extracellular concentration of tryptophan is increased, the rate of transport into the yeast cells reaches a maximum, and fails to increase further even at very high tryptophan concentrations. This observation is a characteristic of which of the following transport systems? a. active transport
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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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Exam2 - Cell Biology / Cell Biochemistry BIOL 4374 / BCHS...

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