Osmosis Notes

Osmosis = Diffusion of H2O Across A Membrane The Plasma Membrane 4/26/2017 Osmosis = Diffusion of H2O Across A Membrane Draw this picture  High H2O potential Low solute concentration Low H2O potential High solute concentration G. Podgorski, Biol. 1010

Osmosis Diffusion of water through a semi-permeable membrane Semi-permeable: permeable to solvents (WATER), but not to large molecules High [water] to low [water] Dissolved molecules (i.e. glucose, starch) are called solutes REMEMBER: Water = solvent Glucose, Starch = solutes

Salt Sucks Salt draws water to where it is. Water wants to equal everything out. A simple rule to remember is: Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.

3 Key Terms Hypo = below Hyper = above Iso = equal

Isotonic Solution The solution the cell is in is equal to the inside of the cell. "ISO" means the same

Hypotonic The word "HYPO" means less There are less solute (salt) molecules outside the cell then inside the cell since salt sucks, water will move into the cell Animal cell could burst Plant cell wall keeps it from bursting

Hypertonic The word "HYPER" means more There are more solute (salt) molecules outside the cell. Water goes in the direction of the salt Cell may die if too much water is lost.

Osmosis in Living Cells Cellulose in cell wall Plasmolysis = cell membrane detaching from the cell wall (shrinking)

Osmosis in Red Blood Cells Isotonic Hypotonic Hypertonic Iso: Normal blood cells Hypertonic solution: the cells shrink Cell may die if too much water is lost. Crenation Hypotonic solution: In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.

Review Passive Transport = _____ Energy used Diffusion is defined as: What occurs in osmosis? Identify the 3 types of solutions.

Effect of Water on Cells Hypertonic Environment High [solute], low [water] Cell shrinks Hypotonic Environment High [water], low [solute] Cell fills with water, too much water can cause the cell to lyse Isotonic Environment [water] = [solute] Normal cell: everything is equal Hypertonic Hypotonic Isotonic

Osmosis in Plant Cells Hypertonic Plasmolysis Hypertonic: In plant cells, the central vacuole loses water and the cells shrink, causing wilting. Hypotonic Hypotonic: In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting