The membrane that surrounds a certain type of living cell has a surface area of

Question

The membrane that surrounds a certain type of living cell has a surface area  of 5.9 x 10-9  m2 and a thickness of 1.5  x 10-8 m. Assume that the membrane behaves like a  parallel plate capacitor and has a dielectric constant of 4.3. (a) The potential on the outer surface of the membrane is +54.8  mV greater than that on the inside surface. How much charge resides on the  outer surface? (b) If the charge in part (a) is  due to K+ ions (charge +e), how many such  ions are present on the outer surface?  

Explanation / Answer

C=A*epsilon/d

C=(5.9*10^-9)*(4.3)/(1.5*10^-8)

Q=CV=(54.8*10^-3)*(5.9*10^-9)*(4.3)/(1.5*10^-8)=0.09268coulomb

b)

No. of ions=Q/e=0.09268/(1.6*10^-19)

Ions K+ present=5.79*10^17

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