How long does it take for a randomly moving protein to travel the distance of a 10-mu m cell diameter, if its diffusion coefficient is 10^-12 m^2/s? Solution t=X2/2D t=Time D=Diffusion coefficient=10-12 m2/s X=mean distance traveled by the protein=10um=10-6 m X2=(10-6)2m=10-12 m2 t=10-12/2*10-12 sec =1/2 Sec So time required for the protein to travel the distance is 0.5 sec..