Passive Transport

Passive Transport● Movement of molecules across a membrane● Uses no energy● Moves down the concentration gradient

(high to low concentration)

High Low Equilibrium

Passive TransportThere are 3 types of passive transport● Diffusion● Facilitated diffusion● Osmosis

Diffusion● The movement of molecules in fluid or gas

until molecules are in equilibrium (evenly spread out)

● Examples: Dye in water, smells● In cells, small lipids, CO2, & O2 diffuse

through the membrane

Diffusion

Facilitated Diffusion● Diffusion across a

membrane with transport proteins

● Proteins only allow a specific particle through

Osmosis● The movement of water

across a semipermeable membrane

● The more particles in a solution means less water, causing a movement of water.

3 Solutions of OsmosisIsotonic● Equal concentration of

particles and water in & out of the cell

● Equal water movement in and out

● Cell stays the same size

3 Solutions of OsmosisHypertonic● Solution has more

particles than inside the cell

● Water leaves the cell

● Cell shrinks

3 Solutions of OsmosisHypotonic● Solution has more water

than inside the cell● Water enters the cell● Cell expands