Question

A spherical cell has a radius of 2.3 μm , and the phospholipid bilayer that constitutes its membrane has a thickness of 3.75 nm . At its normal resting state, the outer membrane is at a voltage of 0V, and the inner membrane is at a voltage of -70mV. The dielectric constant of the cell membrane is roughly 9.0. What is the capacitance of the cell? (Note: the surface area of a sphere is 4πr2)

Answer 1

Step-by-step explanation:

The cell is acting like a shell .

Capacity of a shell is given by the following expression.

C= 4πk ε₀ x ab / (b-a )

k is dielectric constant , b and a are outer and inner radius ε₀ is a constant .

Here a = 2.3 x 10⁻⁶ m

b = 2.3 x 10⁻⁶ + .00375 x 10⁻⁶

= 2.30375 x 10⁻⁶ m

b -a = 3.75 x 10⁻⁹ m .

k = 9

4π ε₀ = 1 / 9 x 10⁹ = .111 x 10⁻⁹

C= .111 x 10⁻⁹ x 9 x 2.3 x 10⁻⁶ x 2.30375 x 10⁻⁶ / 3.75 x 10⁻⁹

= 1.41 x 10⁻¹² F

= 1.41 pF .