Cellmembranes (the walled enclosure arounda cell) are typically about 7.5 nm thick.They are partially permeable to allowcharged material to pass in and out, asneeded. Equal but opposite charge densitiesbuild up on the inside and outsidefaces of such a membrane, and thesecharges prevent additional charges from passing through the cell wall.We can model a cell membrane as a parallel-plate capacitor, with themembrane itself containing proteins embedded in an organic material togive the membrane a dielectric constant of about 10.(a) What is the capacitance per square centimeter of such a cell wall?(b) In its normal resting state, a cell has a potential difference of 85 mVacross its membrane. What is the electric field inside this membrane?
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.
(a) What is the capacitance per square centimeter of such a cell wall?
(b) 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?

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