1. OSMOSIS & TONICITY SEC 4.3 PG 74-75

6. OSMOSIS: -a special case of diffusion involving water -water molecules move across a selectively permeable membrane from an area of high water concentration to an area of low water concentration -does not require ATP energy. -Special channe; proteins allow water to pass through the cell membrane.

7. OSMOSIS Movement of water across a membranes results in: OSMOTIC PRESSURE:buildup of pressure due to osmosis. osmotic pressure acts against HYDROSTATIC PRESSURE to cause changes in osmotic apparatus (thistle tube, u-tube) and in cells. HYDROSTATIC PRESSURE: the pressure of gravity on the solution

10. TONICITY Tonicity refers to the strength of solution in relationship to osmosis. 3 terms to know: 1.Isotonic 2.Hypotonic 3.Hypertonic  The type of solution will determine the movement of water!

11. ISOTONIC SOLUTIONS iso = “the same” tonic = “solution” concentration of solute outside cell is the same as the solute concentration in the cell water moves into cell at equal rate to water moving out cell stays the same, is at EQUILIBRIUM

12. HYPOTONIC SOLUTIONS hypo = “lower” solute concentration OUTSIDE cell = LOWER INTO More water outside cell  water moves INTO cell cell swells LYSIS –bursting may occur in animal cells TURGOR PRESSURE builds up in plant cells  Vacuole pushes outwards against cell wall

13. HYPERTONIC SOLUTIONS hyper= “ higher” solute concentration outside cell is higher water concentration is lower outside cell net movement of water OUT OF cell CRENATION occurs in animal cells PLASMOLYSIS occurs in plant cells

14. D) E) F) A) B) C)