3. Diffusion
• Diffusion: movement of particles from
an area of high concentration to an area
of low concentration.
• the particles will move until they are
evenly distributed.
• many substances move in and out of
cells by diffusion.
• the cell membrane acts like a filter with
extremely tiny openings that allows
only some particles to pass through by
diffusion.
4. Permeable vs Impermeable
• Permeable: Allows liquids or gases to
flow through
• Example: Cotton t-shirt, sponge, soil
• Impermeable: Does not allow liquids
or gases to flow through
• Example: Umbrella, concrete, steel
5. Semi-Permeable
• Semi-permeable (or selectively
permeable): means certain things
cannot cross is but other things can.
• Cell membranes are permeable to water
and smaller particles.This means they
can diffuse across easily.
• Larger particles are impermeable and be
let into the cell through special channels
or gates. Channel proteins or carrier
proteins act as doors to allow larger
particles in an out of cells.
6. Osmosis
• Osmosis: is a special form of
diffusion. It is the diffusion of water
through a selectively permeable
membrane.
• Since membranes are permeable to
water, the water moves based on
concentration.
• MOST IMPORTANT!!!
• Water moves to the high solute
concentration.
