Quiz 2 Solutions

Quiz 2 Solutions - Many drugs(and toxins act on ion...

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Question 1 Assume a cell membrane has ion channels that conduct a single ionic species: Cl-. Assume the chloride ions are pumped so that the concentration is 100 mM outside and 5 mM inside. What is the resting membrane potential of this cell? Provide answer in mV rounded to 2 digits to the right of the decimal. Answer -80.66 Answer range +/- 0.005 Question 2 Assume the membrane potential of a cell is currently at +50 mV, and the conductance to K+ across the membrane is 0.6 nS. If the K+ reversal potential (i.e. battery value) is -90 mV, what is the outward K+ current in pA? Answer 84 Answer range +/- 0.5 Question 3 Current flow through an ion channel is passive, and obeys Ohm’s law as long as a large concentration gradient exists across the membrane. Answer True False Question 4 The following are true of ion channels: Answer They contribute to the establishment of the resting membrane potential. The underlie all rapid voltage signaling.
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Unformatted text preview: Many drugs (and toxins) act on ion channels, often mimicking the action of endogenous neurochemicals. Ions are either pumped or flow passively through ion channels. Ion channels can be represented by a battery and a conductance in series. They mostly have molecular weights in the range of 25K to 250K Daltons. Question 5 Assume you are studying a glial cell whose membrane potential of -90mV is due to a K+ gradient across the membrane. Suppose you dump a potassium salt in the extracellular fluid, which doubles the potassium concentration outside the cell. Which of the following do you expect to happen: Answer The membrane potential will move in the positive direction. The membrane potential will move in the negative direction. The membrane potential will not change. The membrane potential will move gradually to a more positive value as the pumps slowly return the the membrane potential to its equilibrium state....
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