Passive Transport - Diffusion and Osmosis
Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
Diffusion does not require energy, it is a form of passive transport.
Equilibrium occurs when the molecules are evenly spread out across a space.
Facilitated Diffusion
In facilitated diffusion, molecules that cannot cross the phospholipid bilayer, cross the membrane through special protein channels.
Osmosis
Osmosis is the diffusion of water across a selectively permeable membrane.
Water will tend to move toward the area with the highest concentration of solutes.
A simple rule to remember is "SALT SUCKS!"
If a cell is placed in very salty water, the water in the cell will move toward the salt outside the cell.
Types of Solutions
Isotonic: Solution outside the cell is equal to the cell
Hypotonic: Solution outside the cell has fewer solutes, water will move into the cell
Hypertonic: Solution outside teh cell has more solutes, water will move out of the cell.
Example: A cell has a molarity of 0.8 and is placed into a distilled water, which has a molarity of 0.0. The cell has more solutes, therefore water will move into the cell. The cell will gain water and may potentially burst.
Worksheets on Diffusion and Passive Transport
Investigation: How Can Diffusion Be Observed?
Investigation: The Effect of Salt on a Carrot
Diffusion and Osmosis: What Do You Know?
Diffusion and Osmosis Crossword Puzzle