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.