Question

Diffusion is rapid over very short distances, and slow over longer distances. The time, t in seconds, required for diffusion is given by the equation
t = d²/D
where d is the distance in meters a molecule diffuses, and D is the diffusion coefficient (units: m²/sec) of the diffusing molecule. For a small molecule with a D of 2.2 × 10^-9 m²/sec, how long would it take for this molecule to diffuse across a spherical cell with a 22.9 μm diameter?

Answer 1

Given, Diffusion coefficient D = 2.2 times 10^-9 m^2/sec diffusion distance = d = 22.9 mu m time = d^2/D = (22.9)^2 times 10^-12 m^2/2.2 times 10^-9 m^2/sec = 238.36 times 10^-3 = 0.238 seconds Time of diffusion = 238 milli seconds