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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