Transport Mechanisms Transport Mechanisms through Cell Membranesthrough Cell Membranes

Chapter 3.3Chapter 3.3

Passive vs. Active TransportPassive vs. Active Transport

Selectively PermeableSelectively Permeable = cell membrane = cell membrane will only allow some things through!will only allow some things through!

Large macromolecules Large macromolecules and charged ions can and charged ions can NOT get through the NOT get through the lipid bi-layer!!!lipid bi-layer!!!

Passive TransportPassive Transport Movement Movement from high to from high to

lowlow concentrations.concentrations. Does Does NONOT require T require

energyenergy.. 3 Types of Passive 3 Types of Passive

Transport:Transport: DiffusionDiffusion OsmosisOsmosis Facilitated DiffusionFacilitated Diffusion FiltrationFiltration

DiffusionDiffusion

Movement of molecules Movement of molecules from high concentration to from high concentration to low concentration.low concentration.

OsmosisOsmosis

Diffusion of Diffusion of WATERWATER!!!!!!!!!! What happens when you eat popcorn?What happens when you eat popcorn? Why do your fingers get wrinkles when you Why do your fingers get wrinkles when you

swim too long?swim too long? Have you ever put salt on a slug???Have you ever put salt on a slug???

Facilitated DiffusionFacilitated Diffusion Diffusion with the Diffusion with the helphelp of “channel” proteins. of “channel” proteins.

- - Usually because Usually because molecules are too bigmolecules are too big or or have a have a chargecharge and can not go through the membrane alone. and can not go through the membrane alone.

Three Types of Three Types of Solutions Solutions

(Water + Solute/stuff)(Water + Solute/stuff)

HypertonicHypertonic Solutions that Solutions that

have MORE have MORE “stuff” and less “stuff” and less water than the water than the cell.cell.

Water will move Water will move out of cell, out of cell, causing it to causing it to shrivel.shrivel.

HypotonicHypotonic

Solution has LESS Solution has LESS “stuff” and more water “stuff” and more water than the cell.than the cell.

Water will move INTO Water will move INTO cell, causing cell to cell, causing cell to burst.burst.

IsotonicIsotonic Solution has the SAME Solution has the SAME

amount of “stuff” and amount of “stuff” and water as the cell.water as the cell.

There is no net gain or There is no net gain or loss of water from the loss of water from the cell.cell.

This is the IDEAL This is the IDEAL solution that your body solution that your body tries to maintain!!!!tries to maintain!!!!

FiltrationFiltration

Separation of small particles, due to hydrostatic (water) pressure through a selectively permeable membrane.

Active TransportActive TransportMovement Movement from low to highfrom low to high concentration.concentration.Requires Requires ENERGYENERGY..3 Types of Active 3 Types of Active Transport:Transport:

- - Protein PUMPSProtein PUMPS- Endocytosis - Endocytosis (Phagocytosis)(Phagocytosis)- Exocytosis- Exocytosis

Protein “Pumps”Protein “Pumps”Movement of molecules from Low concentration into Movement of molecules from Low concentration into

High concentrations, requiring energy.High concentrations, requiring energy.

Endocytosis or PhagocytosisEndocytosis or Phagocytosis Active transport of large particles INTO the cell, by Active transport of large particles INTO the cell, by

surrounding them with the cell membrane.surrounding them with the cell membrane.

ExocytosisExocytosis

Active transport of substances OUT of the cell Active transport of substances OUT of the cell using the cell membrane.using the cell membrane.

Concentration MountainConcentration Mountain

Passive Transport

Active Transport

DiffusionOsmosisFacilitated Diffusion

Protein pumpsEndocytosisExocytosis

Uses EnergyNo Energy