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OSMOSIS
The Movement of Water
Tonicity: Solution Strength
Osmosis
Tonicity
Hypotonic
Isotonic
Hypertonic
Isotonic
Iso = “the same”
0.9 % NaCl
0.9% NaCl
When the solute
concentration within the
cell is the same on both
sides of the membrane,
there is no net movement
of water
•The cell neither swells or shrinks
Hypotonic
Hypo = “lower” solute concentration
0.9 % NaCl
When a cell is placed in a solution
with a lower percentage of solute
than the cell, the cell will gain
water and increase in mass & size.
0.1% NaCl
•The cell will swell and often burst
Hypertonic
Hyper = “higher” solute concentration
When a cell is placed in a
solution with a higher
concentration of solute than the
cell, the cell will lose water
0.9 % NaCl
5% NaCl
•The cell will shrink and shrivel
http://www.biologie.unihamburg.de/bonline/fo22/osmosis.avi
Solve the Following
B
A
10% Sugar
5% Sugar
Versus
Membrane
Permeable
to sugar
10% Sugar
5% Sugar
Describe what will occur in each thistle tube.
Membrane
Impermeable
to sugar
Solution
A
B
Water level is
unchanged
Versus
10% Sugar
Permeable
membrane
5% Sugar
Since the membrane is permeable, both
sugar and water are able to diffuse.
Sugar will diffuse out of the thistle tube
where it has a higher concentration and
enter the beaker where there is a lower
concentration until both concentrations
are equal.
Water level rises
10% Sugar
Impermeable
Membrane
5% Sugar
Since the membrane is impermeable to
sugar, only water is able to diffuse by
osmosis. Since the beaker contains
95% water, it will enter the thistle tube
where there is less water (90%). Water
will always travel from a higher water
concentration to lower water
concentration.