Download File

Diffusion &
Osmosis
Diffusion
Diffusion is the movement of molecules
from an area of high concentration to an
area of lower concentration
Molecules in solution tend to slowly spread apart over time.
T1
T2
T3
A drop of ink will gradually spread
out through the water to areas
where ink is lower in concentration.
shows how the food odour particles have spread
out through the room because of diffusion
Which molecules will diffuse in
each of the figures below?
1
2
5
3
6
4
ANIMAL CELL PLANT CELL
If all individual cells must interact with their surrounding
environment, what part of the cell controls the movement of
materials in and out of the cell?
CELL MEMBRANES
• Made up of 2 layers of fat
(lipids)
• Are selectively permeable
– allow some substances
but not others to go
through
Compare to…..
permeable – permits passage through
impermeable – does not allow passage through
Diffusion in and out of a cell
The concentration of
oxygen molecules is
greater outside the cell
than inside
sugar +
So the oxygen molecules
diffuse into the cell
O2  CO2
+ H2O + energy
In mammals, birds, reptiles and amphibia, oxygen and carbon dioxide are exchanged
by diffusion in the lungs
blood supply to air sac
diffusion of
oxygen
diffusion of
carbon dioxide
air breathed
in and out
O2
CO2
A single air sac
Earthworm
Section through
worm’s skin
the blood vessels
absorb the O2 and
carry it to the body
diffusion takes place through the thin
skin of the worm
O2 diffuses in
CO2 diffuses
out
Leaf
O2 and CO2
diffuse through
pores in the
epidermis
the ‘veins’
bring water
O2 and CO2 diffuse
into the spaces between cells
OSMOSIS
A special case of diffusion
The movement of water through a selectively
permeable membrane
When concentration of water on one side becomes lower, water
moves through the membrane to balance out the concentration.
OSMOSIS
Salt
Water
Unequal water concentrations;
therefore, water will diffuse from side X to side Y.
Water moves back and forth until a balance is reached
Even after the balance is there the water moleules still move, but in
equal numbers back and forth
Osmosis
Water molecules go through
a semipermeable membrane.
Similarities
Molecules
move around
to create
equilibrium
Diffusion
Molecules spread out
over a large area.
TURGOR PRESSURE
• When water fills the vacuoles and cytoplasm causing
them to swell against the cell wall it exerts this pressure
• Turgor pressure supports plants, causing their leaves and stems to stay rigid
• When concentration of water inside the cell is greater, water moves out and
causes the cell to shrink
• the cell membrane pulls away from cell wall causing the plant to wilt
Can you make GREEN EGGS & HAM????