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 DYE WATER
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 (c) McGraw Hill Ryerson 2007
Diffusion and the Cell Membrane (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
ANIMATION of Osmosis: http://auth. mhhe
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
OSMOSIS TERMS 1 - ISOTONIC the cell stays the same When there is an equal amount of water on both sides of the membrane. the cell stays the same
Examples of Osmosis Example 2: More water moving into cells than is moving out See page 45 (c) McGraw Hill Ryerson 2007
2 - HYPOTONIC the cell expands or bursts When there is more salt inside the cell (and more water outside). the cell expands or bursts
Examples of Osmosis Example 3: More water moving out of cells than is moving in See page 45 (c) McGraw Hill Ryerson 2007
3 - HYPERTONIC the cell shrinks When there is more water inside the cell (and more salt outside). the cell shrinks
hypotonic sol'n isotonic sol'n hypertonic sol'n Take the Section 1.3 Quiz