Electric field inside a cell membrane with 85 mV potential difference

[geyikrali]

Homework Statement

Cell membranes (the walled enclosure around a cell) are typically about 7.5 nm thick. They are partially permeable to allow charged material to pass in and out, as needed. Equal but opposite charge densities build up on the inside and outside faces of such a membrane, and these charges prevent additional charges from passing through the cell wall. We can model a cell membrane as a parallel-plate capacitor, with the membrane itself containing proteins embedded in an organic material to give the membrane a dielectric constant of about 10.

In its normal resting state, a cell has a potential difference of 85 mV across its membrane. What is the electric field inside this membrane?

Homework Equations

V=Ed, E(0)=E/K, c=Q/V

The Attempt at a Solution

I put values V=Ed and get E=[85*10^(-3)]/ [7.5*10^(-9)] = 11.33*10^6
But system says that this answer is not correct.. What should I have to do?

 

[Hootenanny]

You didn't take into account the dielectric medium. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/dielec.html#c2

 

[asterrol]

Masteringphysics is wrong.

 

[Hootenanny]

Masteringphysics is wrong.

Care to expand?

 

[asterrol]

normal resting state means nonpolarized state...

 

[Hootenanny]

normal resting state means nonpolarized state...

Erm... no it doesn't. Even when a neurone is at it's resting potential, the cell membrane is still polarised.