Download PPT

Osmosis
Diffusion of Water
Biology 11
Ms. Lowrie
Selectively Permeable Membrane
Isotonic Solution
Solute & water
concentration:
Equal inside and outside
cell
Water moves in and out
equally
Dynamic equilibrium
Cell size:
Stays the same
= solute
Hypotonic Solution
Solute concentration:
Higher INSIDE cell
Water concentration
Higher OUTSIDE cell
Water moves INTO cell
Cell size:
Grows
 Think: hypo = hippo!
= solute
Hypertonic Solution
Solute concentration:
Higher OUTSIDE cell
Water concentration
Higher INSIDE cell
Water moves OUT OF cell
Cell size:
Shrinks
Think: hyper = sweat
= solute
Osmosis in Plant Cells
Turgor pressure
A type of water pressure
Applies only to plant cells
When is a plant rigid or
wilted?
Depends on water level in
vacuoles
Turgor Pressure
When high:
Vacuole(s) full
Pushes cytoplasm
against cell wall
Keeps plants rigid
Hypotonic
When low (due to
water loss):
Vacuole(s) shrink
Cytoplasm and cell
membrane pull
away from cell wall
Plant wilts
Hypertonic OR
isotonic
Dangerous Water Movement!
Animal
Hypotonic solution
May burst
“Lysed”
Plant
Hypertonic
Cell membrane
pulls away from cell
wall
“Plasmolysis”
Extra Questions
1. What determines whether water will
enter or leave a cell?
 Concentration of solutes or water
2. Why will a goldfish die if it is placed in
salt water?
 Hypertonic situation
 Goldfish cells will give off water
Any Questions???
Let’s review!