Cellular Transport UnitCellular Transport Unit

Passive TransportPassive Transport = = movement of substances movement of substances across the cell membrane across the cell membrane without any input of without any input of energyenergy by the cell by the cell

Passive TransportPassive Transport

TypesTypes1) Diffusion 1) Diffusion = movement of = movement of molecules from high to low molecules from high to low [ ] (concentration)[ ] (concentration)- driven by the - driven by the concentration gradientconcentration gradient

- spreads out evenly till - spreads out evenly till dynamic equilibrium is dynamic equilibrium is reachedreached

DiffusionDiffusion

2) Osmosis 2) Osmosis = diffusion of water= diffusion of water

A solution may be one of the A solution may be one of the following: (compared to a cell)following: (compared to a cell)

- isotonic solution: same [ ] of - isotonic solution: same [ ] of water and solutewater and solute

- hypotonic solution: lower [ ] - hypotonic solution: lower [ ] of solute, a lot of waterof solute, a lot of water

- hypertonic solution: higher [ - hypertonic solution: higher [ ] of solute, less water] of solute, less water

Isotonic Solution (Red Isotonic Solution (Red Blood Cells)Blood Cells)

A solution is A solution is isotonic to a cell isotonic to a cell if it has the same if it has the same concentration of concentration of solutes as the solutes as the cell. cell. Equal Equal amounts of amounts of water enter and water enter and exitexit the cell, so the cell, so its size stays its size stays constant.constant.

Hypotonic Solution (Red Hypotonic Solution (Red Blood Cells)Blood Cells)

A hypotonic A hypotonic solution has solution has fewer solutes fewer solutes than a cell. than a cell. Overall, Overall, more more water enterswater enters a a cell in a cell in a hypotonic hypotonic solution, causing solution, causing the cell to expand the cell to expand and even burst.and even burst.

Hypertonic Solution (Red Hypertonic Solution (Red Blood Cells)Blood Cells)

A hypertonic A hypertonic solution has more solution has more solutes than a solutes than a cell. Overall, cell. Overall, more water more water exitsexits a cell in a a cell in a hypertonic hypertonic solution, causing solution, causing the cell to shrivel the cell to shrivel and even dieand even die

Direction of OsmosisDirection of OsmosisOutside the Cell Inside the Cell Outside the Cell Inside the Cell NetNet Movement of Movement of

WaterWater

Isotonic Isotonic Isotonic Isotonic None None HypotonicHypotonic Hypertonic Hypertonic Inside the CellInside the Cell Hypertonic Hypotonic Outside the CellHypertonic Hypotonic Outside the Cell

** If the solution outside the cell is hypotonic, then inside the cell is hypertonic and vice versa** Water tends to diffuse from hypotonic to hypertonic

- Plasmolysis = cells shrink - Plasmolysis = cells shrink when turgor pressure is lostwhen turgor pressure is lost- the reason plants wilt- the reason plants wilt

- Cytolysis = cell bursts due - Cytolysis = cell bursts due to water entering the cellto water entering the cell

3) Facilitated Diffusion3) Facilitated Diffusion

= move molecules across = move molecules across the cell membrane the cell membrane through carrier/transport through carrier/transport proteins proteins

- are specific for the type - are specific for the type of molecule they help of molecule they help diffusediffuse

Facilitated Diffusion (Open Facilitated Diffusion (Open Channels)Channels)

Facilitated Diffusion Facilitated Diffusion (Proteins Change Shape)(Proteins Change Shape)

Diffusion vs. Facilitated Diffusion vs. Facilitated DiffusionDiffusion

DiffusionDiffusion Facilitated Diffusion Facilitated Diffusion

Active TransportActive Transport = = substances can cross substances can cross the cell membrane the cell membrane with with an input of energyan input of energy from the cellfrom the cell

Active TransportActive Transport

1) Endocytosis1) Endocytosis = the process = the process by which cells ingest “stuff”by which cells ingest “stuff”

- vesicle holds the “stuff”- vesicle holds the “stuff”

- two types:- two types:

1) pinocytosis - solutes and 1) pinocytosis - solutes and fluidsfluids

2) phagocytosis - large 2) phagocytosis - large particles or whole cellsparticles or whole cells

EndocytosisEndocytosis

2) Exocytosis 2) Exocytosis = the = the process by which cells process by which cells release “stuff”release “stuff”

- is essentially the reverse - is essentially the reverse of endocytosisof endocytosis

ExocytosisExocytosis