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OSMOSIS The diffusion of water molecules through a membrane
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Diffusion and Osmosis
DIFFUSION• The process in
which molecules move from areas of HIGH concentration to areas of LOW concentration
OSMOSIS• The diffusion of
water molecules through a membrane
Osmosis
• The diffusion of water across a selectively permeable membrane.
• Osmosis is a type of Passive Transport.
• Osmosis requires NO ENERGY.
When do the molecules stop moving?
EQUILIBRIUM = molecules are evenly distributed
Let’s Practice…
OsmosisOsmosis• Hypertonic- a solution
that causes a cell to shrink because of Osmosis.
• Hypotonic- a solution that causes a cell to swell because of Osmosis.
• Isotonic- a solution that causes no change in the size of the cell
Why are osmosis & diffusion important?
• All living things have certain requirements they must satisfy in order to remain alive – maintain homeostasis
• These include exchanging gases (usually CO2 and O2), taking in water, minerals, and food, and eliminating wastes.
• These tasks happen at the cellular level.• Molecules move through the cell membrane by
diffusion• A balance, or EQUILIBRIUM, must be maintained.
Summary• Diffusion is the movement of molecules from an
area of higher concentration to an area of lesser concentration.
• Osmosis is the movement of water thru a semi permeable membrane.
• Active transport requires energy. (molecules move from an area of lesser to higher concentration)
• Passive transport needs NO ENERGY! (molecules move from an area of higher to lesser concentration).
Let’s Practice…
• 1. The concentration of oxygen particles inside a cell is 45 percent and outside the cell is 30 percent. Draw a picture in your notes of this scenario.
• What will most likely happen? A. The Oxygen will move from inside to outside.– B. The Oxygen will move from outside to inside.– C. Nothing – its isotonic
Let’s Practice…
• 2. The concentration of water molecules inside a cell is 80 percent and outside the cell is 25 percent. Draw a picture in your notes of this scenario.
• What will most likely happen?– A. The Water will move from inside to outside.– B. The Water will move from outside to inside.– C. Nothing – its isotonic
Let’s Practice…
• 3. The concentration of hydrogen particles inside a cell is 33 percent and outside the cell is 62 percent. Draw a picture in your notes of this scenario.
• What will most likely happen?– A. The Hydrogen will move from inside to outside.– B. The Hydrogen will move from outside to inside.– C. Nothing – its isotonic
Let’s Practice…
• 4. The concentration of water molecules inside a cell is 52 percent and outside the cell is 51 percent. Draw a picture in your notes of this scenario.
• What will most likely happen?– A. The water will move from inside to outside.– B. The water will move from outside to inside.– C. Nothing – its isotonic
Let’s Practice…
• What is your prediction for this diagram?• Address BOTH the Salt and the Water
molecules.
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