Download 8.3 Cell surface area

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