Diffusion is the movement of molecules from an area of high concentration to low concentration, while osmosis is a type of diffusion where water moves through a selectively permeable membrane. There are three types of solutions where osmosis can occur: isotonic solutions where water levels are equal inside and outside the cell; hypertonic solutions where there is more water outside the cell, causing it to shrink; and hypotonic solutions where there is more water inside the cell, causing it to expand. A cell wall is a rigid membrane that can be affected by osmosis through changes in water levels inside and outside the cell.

1. Diffusion Vs. Osmosis
Biology

2. Definitions
• Diffusion:
– Movement of molecules
from a place where there is
a large amount (high
concentration) to a place
where there is none or a
smaller amount (low
concentration).
• Osmosis:
– Diffusion of water across a
selectively permeable
membrane

3. Diffusion Diagram
• High Concentration
• Low Concentration
EquilibriumDiffusionBeginning

4. Osmosis Diagram
• Selectively Permeable
Membrane: Some
substances can pass
through and some cannot.

5. 3 Types of Solutions where OSMOSIS
can take place
• 1. ISOTONIC – amounts of water
are equal inside and outside of
the cell (EQUILIBRIUM)
93%
93 % 93 %
93%
93%

6. 3 Types of Solutions where OSMOSIS
can take place
• 2. HYPERTONIC – amount
of water inside the cell is
greater than outside of the
cell. (CELL SHRINKS)
85%
85% 85%
85%
93%

7. 3 Types of Solutions where OSMOSIS
can take place
• 3. HYPOTONIC – amount of
water inside the cell is less
than outside of the cell.
(CELL EXPANDS)
98%
98% 98%
98%
93%

8. Osmosis & Cell Wall
• Cell wall is a rigid
membrane, how is it
affected by osmosis?