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Biology 2: Systems, Lecture 2 Question 27 pg 49
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Korolos_5348
#1 Posted : Saturday, June 27, 2020 2:58:01 PM
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Hello,

I just had a question regarding number 27 in the nervous system lecture. The question states that the membrane is impermeable to K+ ions but the Na+/K+ pump is working normally. The Na+/K+ pump moves 3Na+ ions out of the cell and brings 2K+ into the cell. These charges are not equal (+3 vs +2) so there is a net positive charge of +1 leaving the neuron making the inside of the cell more negative. Thus, wouldn't the resting potential become more negative (option C)? The answer key says that A is correct. Would you please clarify this?

Thank you in advance
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INSTR_Rheann_72
#2 Posted : Saturday, June 27, 2020 4:23:57 PM
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This is a tricky question. At first glance you would assume that if less + ion was going into the cell the resting potential would be more negative. However, the Nernst equation doesn't just include potassium, it also includes sodium. When the permeability of potassium decreases, its contribution to the resting potential decreases and is less significant than sodium. Sodium's resting potential is more positive, and so you would expect the resting potential to become more positive.


If you were able to et to A or C that is great for a question like this!
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