Transcript Osmose and diffusion

Osmose and diffusion
Selective permeability
Review: the cell membrane controls the exchanges done
between the exterior of the cell and the interior of the cell.
If the cell membrane lets only certain substances go in or go out
of the cell, we say it is has selective permeability.
Only certain
molecules are allowed
in or out of the cell
Diffusion
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Diffusion is the movement of particles of solute.
From an area of high concentration
to low concentration
It is by diffusion that particles enter and exit the cell.
The semi-permeable membrane lets the solute particles travel
through because they are small.
Examples of diffusion
• The yellow food coloring that we put in water diffuses until it
is equal all over the water:
• When someone cooks, the smell disperses all
over the house.
• It goes from most concentrated (the kitchen)
to least concentrated (a bedroom)
Osmosis
-The cell is composed of 70% of water
-Molecules of water are small and can pass through the cell
membrane.
-Osmosis is the movement of the water, which is the solvent.
If the solute if too big to go through the cell membrane, the
water will go through instead.
-The movement of the water is determined like diffusion:
-Most concentrated area of water
to an area of less
water
-This is done to dissolve the area that doesn’t have enough
water.
The sugar molecule is too big to go through the
membrane, so the water will go through.
Interesting web sites!
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__how_diffu
sion_works.html
http://www.wiley.com/legacy/college/boyer/0
470003790/animations/membrane_transport/
membrane_transport.htm
Animal
Cell
Plant cell
Result:
Hypotonic
Isotonic
Hypertonic
Here, there is not
enough water
inside the cell, so
the water from the
outside goes in.
Here the
concentrations are
equal: ideal
situation
Here there is not
enough water
outside of the cell,
so the water must
must come out.
The cell inflates
The cell’s shape
does not change
The cell shrivles.