Download - Passive Transport
Cellular Transport
‘07 Biology
2 Types:
PassiveNo energy!
ActiveEnergy!
Passive TransportSubstances are allowed to cross the cell
membrane without any input of energyRemember: The cell membrane is
“selectively permeable”
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Types of Passive TransportDiffusionFacilitated DiffusionOsmosis
DiffusionMovement of molecules from areas of
high concentration to lowHow does it work?“Kinetic energy” (energy in motion)Concentration gradient- caused by a
difference in concentrationDiffusion results in equilibrium (all
molecules occupy the same amount of space)
Facilitated DiffusionSome molecules are helped across the
cell membrane by carrier proteinsNo energy is required in this process
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OsmosisThe diffusion of water across the
cell membraneThe direction of osmosis depends
on the concentration of solutes inside and outside the cell
Osmosis (continued)Hypotonic- concentration of solutes
outside the cell is lower than the concentration inside
Hypertonic- concentration outside is higher than inside
Isotonic- concentrations inside and out are equal
Direction of Osmosis
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Active TransportSometimes cells must move molecules
against the concentration gradientThis process requires energy (ATP)
and special protein “pumps”
Sodium-Potassium PumpSpecial proteins within the membrane
that transport Na+ and K- ionsSome cells must have a higher
concentration of Na+ ions outside of the cell and a higher concentration of K- ions inside the cell
2 Potassiums are brought in for every 3 Sodiums removed
Sodium-Potassium Pump
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Movement In VesiclesSome molecules are too big to be
transported across the cell membrane by passive and active transport
Endocytosis- “cell eating”Exocytosis- “cell pooping”
EndocytosisProcess by which cells ingest
macromolecules, fluids, large particles and even other cells
These molecules are enclose in a bubble of membrane (vesicle) that pinches away from the cell membrane
Endocytosis (continued)Pinocytosis- ingestion of small
particles and fluidPhagocytosis- ingestion of large
molecules or other cells
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ExocytosisProcess by which waste and large
particles are released from the cellA vesicle will fuse with the membrane,
releasing its contents into the extra cellular environment
Endocytosis/Exocytosis
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