L.O: to define diffusion and facilitated diffusion
to state factors affecting diffusion
Starter: Recap on Osmosis
a) What would happen to a red blood cell placed
in a solution with low water potential (hypotonic)?
b) What would happen to a plant cell placed in a
solution with lower water potential (hypotonic)?
L.O: to define diffusion and facilitated diffusion
to state factors affecting diffusion
Transport across the cell membrane
All cells are surrounded by a partially-permeable membrane
that controls what substances can enter and exit the cell.
A cell needs to be able to import
the substances it needs to
survive, and to export waste
materials and substances that
are needed outside the cell.
There are several methods by which substances (molecules
and ions) can cross the cell membrane:

diffusion

osmosis

active transport.
The movement of molecules or ions from a region
of high concentration to a region of low
concentration.
It is a passive process, so requires no ATP
(energy).
• http://mrhardy.wikispaces.com/Diffusion.s
wf
Facilitated Diffusion?
What on earth is it?
Discuss in pairs
Facilitated Diffusion
Diffusion involving the presence of protein
carrier molecules to allow the passive
movement of substances across a plasma
membrane.
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation_
_how_facilitated_diffusion_works.html
L.O.2 Factors Affecting Diffusion
• There are 4 factors affecting diffusion
• You investigated one factor during the
induction lesson back in July….!
• You have just seen another factor during
the demo
• Think and discuss what the other two
factors could be
Fick’s Law
Movement Across the Membrane
Diffusion
Direction
along conc.
gradient
ATP
(energy)
needed?
Carrier /
channel
proteins
used?
What is
moved?
Facilitated
Diffusion
Osmosis
Active
Transport
Movement Across the Membrane
Direction
along conc.
gradient
ATP
(energy)
needed?
Carrier /
channel
proteins
used?
What is
moved?
Diffusion
Facilitated
Diffusion
Osmosis
Down
Down
Down
No
No
No
No
Yes
No
Molecules Molecules
Water
Active
Transport