Osmosis

Osmosis

OsmosisMovement of Water across the Cell Membrane

Lets review diffusion!Diffusion requires NO ENERGYMolecules move from HIGH to LOWDownhill!!!! Lets see!Osmosis:Movement of WATER from an area of more water (H) to an area of less water (L)Water moves OPPOSITE of other molecules!

How does osmosis work?Across a SEMI-PERMEABLE membraneOnly certain molecules, like water, can move freely across the membraneWater molecules move from HIGH to LOWThey want to BALANCE OUT a solutionTherefore, water moves OPPOSITE of other moleculesExample of Osmosis #1Condition #1: More Water outside of cellInside cell = 98% Water, 2% saltOutside cell = 100% Water, 0% salt

Water moves into cell, salt moves out to balanceCELL SWELLS orBURSTS!98%L100%HExample of Osmosis #2Condition #2: More water inside of cellInside cell: 98% Water, 2% SaltOutside cell: 95% Water, 5% SaltWater moves out of cell, salt moves in to balanceCELL SHRIVELS!98%H95%LOsmotic PressureCells behave differently when placed in different solutions!This is due to OSMOSIS!Most cells are ~ 98% water!Three types of osmotic pressure:HypotonicHypertonicIsotonicHypotonic ConditionCell is placed in 100% waterSolution outside of cell has MORE water, less of other materials (i.e., salt)Therefore, solution is below strength (hypo)CLICK HERE FOR DEMO!98%Water ENTERS cell100%CELLSWELLS!Hypertonic ConditionCell is placed in 95% waterSolution outside of cell has LESS water, more of other materials (i.e., salt)Therefore, solution is above strength (hyper)CLICK HERE FOR DEMO!Water LEAVES cell98%95%CELL SHRINKS!Isotonic ConditionCell is placed in 98% waterSolution outside of cell has SAME water, same amount of other materials (i.e., salt)Therefore, solution is equal strength (iso)

Water moves equally; Equilibrium exists98%98%CELLSTAYSTHE SAME!Review of Osmosis