Diablo® III

Cell membrane question

The tendency for Na+ to move into the cell is due to:

a) the higher numbers of Na outside the cell resulting in a chemical concentration gradient.
b) the net negative charge inside the cell attracting the positively charged Na+
c) the attractive force of K+ inside the cell pulling Na+ into the cell.
d) all of the above.
e) A and B only.

Thanks!
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im thinking A..

net charge affecting permeability? not too sure...
k/na pump.. ok, but it shouldnt affect concentration gradient for Na
Edited by Obechu#1116 on 10/23/2012 10:05 PM PDT
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I'm thinking A as well. Of course I am responding almost two months too late.

A is referring to osmotic pressure.

Regarding B, I don't think you can have a net negative charge inside the cell. You might have one specific part of the cell, such as one side of a single layer membrane or one side of one of the layers that makes up a multi-layer membrane. Phospholipids that form such membranes have a polar end and a non polar end and it is possible that one of those ends could have a negative charge while the other end has a positive charge, with an overall neutral charge for the phospholipid as a whole.

Regarding C, positive ions do not attract other positive ions, unless there is some intermediate step that is being left out, like positive ions attract negative ions, which in turn attract other positive ions or something weird like that.

Of course it's entirely possible that you have a professor who thinks one thing and types something completely different. I have a professor who typed "rice" as one of the multiple choice answers on an ecology based course. He meant to type "rice paddy" as the choice and graded it as such. I did not select rice as the correct answer. I would have selected "rice paddy" as the correct answer. So, maybe for part B your professor means something slightly different from what he actually typed.
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