1.3 Transport in cells

Medium58%

The rate of diffusion of a solute across a cell membrane can be modelled using Fick's Law:

\text{Rate of diffusion} \propto \frac{\text{Surface Area} \times \text{Concentration Difference}}{\text{Thickness of Membrane}}

A student compares diffusion in two spherical model cells, as shown in the diagram:

Comparison of diffusion into two model cells of radius r and 2r

Both cells are exposed to the same external solute concentration difference, and both have identical membrane thicknesses.

If the radius of the model cell is doubled from $r\,$ to $2 r$ , how does the initial rate of diffusion per unit volume of the cell change?

It is halved (multiplied by a factor of $0.5$ )

It is quartered (multiplied by a factor of $0.25$ )

It is doubled (multiplied by a factor of $2.0$ )

It is quadrupled (multiplied by a factor of $4.0$ )

1.3 Transport in cells Questions