NS FL 8 Bio/Biochem #48

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NS FL 8 Bio/Biochem #48

Post by ESTEBAN227 » Mon Jan 07, 2019 12:50 pm

Hi all! So I had a question in regards to the explanation of this question. Wouldn't the cell want to have an interior charge that is negative and an extraneuronal charge that is positive, so that depolarization could occur? Wouldn't this then mean that the permeabiliy fo Cl- be high and low for K+?

I was just thinking this because in regards a normal cell, 2K+ in pumped into the cell and 3Na+ are pumped out of the cell generating a negative charge on the interior of the cell. So would the same logic apply to this question?

Thanks for your help!
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Re: NS FL 8 Bio/Biochem #48

Post by NS_Tutor_Will » Mon Jan 07, 2019 5:46 pm

Thanks for the question!

Your reasoning is solid, but in this case, we're actually looking to initiate an action potential. So, while we would want to have a resting potential that's negative (which would align with what you're saying), the question is actually asking us how we would get depolarization to occur. Thus, we actually want potassium to enter the cell, as that would cause the cell to reach its threshold potential and begin the action potential. If Cl- were allowed to enter, we'd have hyperpolarization and an action potential would be less likely.

Basically, if the question asked, how do we get the cell to proper resting potential, your reasoning is perfect. But, in this case, since it's asking how to depolarize, D is the correct answer. You approached it as "how do we generate resting potential so that depolarization can occur" rather than "how do we get depolarization to occur" — hopefully that makes sense!

Good luck with your prep!
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