Download Cell Membrane

Osmosis
Osmosis: the diffusion of water molecules
through a selectively permeable membrane.
• Water moves
from high to low
concentration.
• Is the membrane
permeable to the
water or the
solute? How
can you tell?
Osmosis
Tonicity: Determines the direction of
water movement due to osmosis.
• Hypertonic: the solution with a
greater concentration of the solute.
– A cell would lose water and shrink
if it is placed in a hypertonic
solution.
– Plasmolysis: when the cell
membrane of a plant cell pulls
away from the cell wall.
– Causes the plant to wilt due to a
lack of osmotic pressure.
Osmosis
Tonicity: Determines the direction of
water movement due to osmosis.
• Hypertonic: the solution with a
greater concentration of the solute.
– A cell would lose water and shrink
if it is placed in a hypertonic
solution.
– Plasmolysis: when the cell
membrane of a plant cell pulls
away from the cell wall.
– Causes the plant to wilt due to a
lack of osmotic pressure.
Osmosis
• Hypotonic: the solution with the
lesser concentration of the solute.
– A cell would gain water and
swell if it is placed in a
hypertonic solution.
– Cytolysis: when a cell bursts
because of osmotic pressure.
– Turgor Pressure: the pressure
created when the cell
membrane pushes against a cell
wall.
Osmosis
• Isotonic: concentration of
the solute is the same on
both sides of the membrane
(equilibrium).
– Cells will stay the same size
in a isotonic solution, there is
no net movement of water
molecules.
http://www.glencoe.com/sites/common_ass
ets/science/virtual_labs/LS03/LS03.html
10% NaCL
90% H2O
CELL
20% NaCL
80% H2O
What is the direction of water movement?
Cell in Hypertonic Solution
15% NaCL
85% H2O
ENVIRONMENT
CELL
5% NaCL
95% H2O
What is the direction of water movement?