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…

Osmosis Osmosis 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.