Diffusion: Random movement of molecules from an area of high (many) concentration to an area of low (few) concentration.
Examples of Diffusion:
c. Movement of food across intestinal wall.
d. Movement of air across lung wall.
Membrane: Barrier (thin wall)
Types of membranes in living things
1. Permeable: Has large hole in it to let most molecules pass through.
2. Semi-permeable: Membrane having smaller holes so only molecules smaller than holes pass through. Most cells have semi-permeable membranes.
3. Impermeable: Membrane with no holes. Molecules can not pass through.
The diffusion of water through a semipermeable membrane from high concentration to low concentration.
Importance of Osmosis:
a. Movement of water into roots.
b. Food preservation (sugar, salt, preservatives draw water out of molds or germs).
c. Weed killing.
d. Filtering urine through kidneys
e. Movement of water across intestine walls.
f. Dialysis/ kidney machine.