101midterm_1_sample_08_key

101midterm_1_sample_08_key - 1. The lipid bilayer of the...

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1. The lipid bilayer of the cell membrane… a. is due primarily to the presence of cholesterol. b. is due to the presence of hydrophilic and hydrophobic groups on the membrane’s triglycerides. * c. is formed as a result of the arrangement of phosphate and fatty acid groupings in the membrane’s phospholipids. d. is the result of translational movement of membrane proteins. e. b and c. 2. The establishment of a Gibbs-Donnan equilibrium across a semi-permeable membrane… * a. reflects the point at which the force of diffusion of an ion to which the membrane is permeable is exactly offset by the force of attraction of that ion by the counterion to which the membrane is not permeable. b. results in a voltage across the membrane that can be accurately predicted by the Nernst Equation for up to three permeant ions. c. is possible only if an active pump mechanism is functioning, even in an artificial membrane. d. a and b. e. None of the above. 3. An artificial membrane is highly permeable to Cl - and completely impermeable to its counterion K + . The concentration of KCl on one side of the membrane is 75 mM and on the other is 10 mM. The potential difference generated across the membrane at 25 o C will be… * a. less than 58 mV. b. greater than 58 mV. c. zero. d. negative. e. b and d. 4. You are experimenting with a neuron in the laboratory. The neuron is immersed in a solution that is identical to normal extracellular fluid. Decreasing the internal concentration of K + will… * a. decrease resting membrane potential. b. increase resting membrane potential. c. not affect resting membrane potential. d. hyperpolarize the cell. e. b and d.
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5. A person suffers from a strange disease whereby his neurons have no voltage- sensitive potassium channels. As a consequence… a. the rate at which an action potential reaches its peak would be slower than normal. b. there would be no absolute refractory period. c. following generation of an action potential, recovery to normal resting membrane potential would be faster than normal. * d. following generation of an action potential, recovery to normal resting membrane potential would be slower than normal. e. a and c. 6. In the laboratory, you record action potentials while a neuron is immersed in a physiological saline solution. You find that the amplitude of the action potentials decreases as you lower the external sodium concentration. a. This observation is impossible because it would be a violation of the all- or-none law for action potentials. b. This couldn’t happen because, if anything, decreasing external sodium concentration would make the amplitude of the action potentials greater. * c. This is a perfectly understandable observation because the amplitude of the action potential is determined, in part, by the concentration gradient for sodium. d.
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This note was uploaded on 07/07/2009 for the course NPB NPB 101 taught by Professor Weidner/wingfield during the Spring '08 term at UC Davis.

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101midterm_1_sample_08_key - 1. The lipid bilayer of the...

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