Factors Affecting Cell Membrane Transport

Surface Area to Volume Ratio

Cells depend on their cell membrane to receive inputs and remove wastes, so their surface area to volume ratio is very important.

As cells increase in size, their surface area to volume ratio decreases.

Some cells have a specialised shape that can increase their surface area to volume ratio.

(The higher the surface area to volume ratio, the higher the rate of diffusion.)

Concentration Gradient

The difference in concentration that brings about diffusion is known as a concentration gradient (diffusion gradient)

The greater the difference between the two concentrations, the faster the rate of diffusion. (As the concentration gradient increases, the rate of diffusion increases.)

Physical Nature of Materials Being Exchanged

Larger molecules will be diffused slower, and may be too large to move through the cell membrane. (Generally speaking, the larger the molecule the slower the rate of exchange.)

Chemical Nature of Materials Being Exchanged

Non-polar molecules (oxygen, carbon dioxide) diffuse readily through the cell membrane, whereas polar molecules (such as glucose) need to use proteins.