Download 1.3 Diffusion, Osmosis, and the Cell Membrane • Diffusion is the

1.3 Diffusion, Osmosis, and the
Cell Membrane
•  Diffusion is the movement of particles from an area of
higher concentration to an area of lower
concentration.
•  Concentration is the amount of substance in a given
space.
•  The smell of fresh baked bread “spreading”
throughout the room is an example of diffusion.
The diffusion
of ink in water.
See pages 40 - 41
(c) McGraw Hill Ryerson 2007
Diffusion and the Cell Membrane
•  The cell membrane is a selectively permeable membrane.
w  This means that it has many small openings that let some substances
pass through it but not others.
•  One way that substances can move through the cell membrane is
by diffusion.
•  When the concentration on both sides of the membrane is the
same, it is called equilibrium.
See page 42
(c) McGraw Hill Ryerson 2007
Osmosis
•  Osmosis is the diffusion
of water through a
selectively permeable
membrane.
•  Osmosis occurs when
water particles move
from a higher
concentration to a
lower concentration.
See page 43
(c) McGraw Hill Ryerson 2007
Osmosis and the Cell
•  Cells contain water and need this water to survive.
•  Osmosis is how the cell gains and loses its needed
water.
Explain how placing this wilted
flower in water will cause the flower
to “straighten up”.
See pages 43 - 44
(c) McGraw Hill Ryerson 2007
Examples of Osmosis
Example 1: Equal movement of water in and out of cells
See page 45
(c) McGraw Hill Ryerson 2007
Examples of Osmosis
Example 2: More water moving into cells than is moving out
See page 45
(c) McGraw Hill Ryerson 2007
Examples of Osmosis
Example 3: More water moving out of cells than is moving in
See page 45
(c) McGraw Hill Ryerson 2007