Tonicity is a measure of the osmotic pressure (as defined by the water potential of the two solutions) of two solutions separated by a semipermeable membrane.

 Solute – substance being dissolved in the solution  Solvent - substance in which a solute is dissolved to form a solution  Concentration- the amount of solute per unit of solvent. Review

 Osmosis - diffusion of water through a selectively permeable membrane.  The flow of water from an area of high concentration to an area of low concentration Water never stops moving, even when equilibrium has been reached.Tonicity

 The net movement of water across the semipermeable membrane is equal.  The amount of water entering a cell is the same as the amount leaving the cell  Isotonic plant cells are flaccid.IsotonicSolutions

 The amount of solute inside the cell is higher than outside. The water concentration will try to even out.  Water will enter the cell. This causes the cell to swell (get larger), it may burst.  Hypotonic plant cells are turgid.  The process of swelling animal cells is called hemolysis. Placing a cell in plain water Hypotonic Solution

 The amount of solute inside the cell is less than outside. The water concentration will try to even out.  Water will leave the cell. This causes the cell to shrink (get smaller)  Hypertonic plant cells are plasmolyzed.  The process of shrinking animals cells is called crenation Placing a cell in salt water Hypertonic Solution

Tonicity of Solution Concentration of Solute (outside of cell) Water (outside of cell) Net Movement End Product IsotonicSame as cell None Hypotonic Less than cell More than cell Cell gains water Swells, turgor pressure Hypertonic More than cell Less than cell Cell loses water Shrinks plasmoly sis

 hill.com/sites/ /student_view0/c hapter21/animation__hemolysis_and_crenati on.html hill.com/sites/ /student_view0/c hapter21/animation__hemolysis_and_crenati on.html  Lets watch a clip and answer questions about red blood cells in different solutions.