1. 3.4 Diffusion and Osmosis
KEY CONCEPT Materials move across membranes because of concentration differences.

2. 3.4 Diffusion and Osmosis Passive transport:
does not require energy input from a cell.
Molecules can move across the cell membrane from high to low 2.
There are two types of passive transport.
diffusion –movement of materials from high to low concentration
osmosis –movement of water from high to low concentration

3. 3.4 Diffusion and Osmosis
Diffusion and osmosis are types of passive transport.
There are three types of solutions.
Isotonic
Draw arrows
Label isotonic=
iso means same
hypertonic
Draw arrows
Label hypertonic=
hyper shrinks away
(like a hyper kid)
Hypotonic
5. Draw arrows
Label hypotonic
hypo swells and cell will burst

4. 3.4 Diffusion and Osmosis
Some molecules can only diffuse through transport proteins.
Some molecules cannot easily diffuse across the cell membrane.
Facilitated diffusion is diffusion through transport proteins.
Sugar molecules need help so the transport molecules facilitate the movement