Surface Area If diffusion across the cell membrane

Surface Area

If diffusion across the cell membrane or within the cell is too slow, the cell won’t get what it needs fast enough and will be inefficient and could die.

How can the diffusion rate of substances in and out of cells be increased?

a. Concentration Gradient: concentration gradient diffusion speed

b. Cell size: cell size diffusion into, out of and through cell because Surface Area: Volume ratio

Size and number of pores in membrane: pore size or number diffusion

d. Temperature: Temperature diffusion speed

Surface Area-to- volume ratio Calculation = Surface area of cell / volume of the cell.

If the surface area to volume ratio is too small there is not enough membrane surface for diffusion, and it takes too long for substances to diffuse through the cell.

Cells need a high SA: VOL ratio. IT IS BETTER TO BE A SMALL CELL! cellsize SA: vol ratio

SA/Vol ratio problems limits cell size This is why multi-celled organisms have to have quabillions of small cells instead of being just one HUMUNGOUS cell

Cell Shape Cells’ surface areas (SA) are increased in ingenious ways so there is lots of cell membrane surface to increase sites for diffusion and activity.

Irregular shaped cell membrane microvilli