(c) McGraw Hill Ryerson 2007

1.3 Diffusion, Osmosis, and theCell 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.

See pages 40 - 41

The diffusion of ink in water.

DYE

WATER

(c) McGraw Hill Ryerson 2007

Diffusion and the Cell Membrane

• The cell membrane is a selectively permeable membrane. 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

Diffusion and the Cell Membrane

(c) McGraw Hill Ryerson 2007

(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

ANIMATION of Osmosis: http://auth.mhhe.com/biosci/genbio/animation_quizzes/graphics/lem4s4b.ram

(c) McGraw Hill Ryerson 2007

Osmosis and the Cell

See pages 43 - 44

• 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”.

(c) McGraw Hill Ryerson 2007

Examples of Osmosis

See page 45

Example 1: Equal movement of water in and out of cells

When there is an equal amount of water on both sides of the membrane.

(c) McGraw Hill Ryerson 2007

Examples of Osmosis

See page 45

Example 2: More water moving into cells than is moving out

When there is more salt inside the cell (and more water outside).

(c) McGraw Hill Ryerson 2007

Examples of Osmosis

See page 45

Example 3: More water moving out of cells than is moving in

When there is more water inside the cell (and more salt outside).

Take the Section 1.3 Quiz