1. Surface Area

2. 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.

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

4. a. Concentration Gradient: concentration gradient diffusion speed

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

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

7. d. Temperature:
 Temperature
 diffusion speed

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

9. 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.

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

11. 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

12. 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.

13. Irregular shaped cell membrane
microvilli