Cell membranes (the walled enclosure around a cell) are
typically about d = 7.3 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 61. A. What is the capacitance per
square centimeter of such a cell wall? Express your answer using
two significant figures. 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? Express your answer using two
significant figures.