Question

What is the energy stored in such a cell membrane if the potential difference across it is 7.05×10−2 v?

Answer 1

Capacitance
C= e A/d
or C=Q/V
Energy stored in the capacitor
W=0.5CV^2

This a straight forward problem
W=0.5 e A/d (V^2)
W=0.5 x 4.5 x 4.75 x 10^-9 m^2 / 8.5 x 10^-9
m=
W=...

since d is the thickness and the energy is inversely proportional to energy stored in the capasitor then with the increase of the thickness of the membrane the energy will decrease.