Cell Transport

Diffusion•The cytoplasm is a “solution” of many

substances in water.•Concentration=mass/volume•Diffusion is the process by which molecules

move from an area of high concentration to an area of low concentration.

(Basically, from where there are more molecules to where there are less molecules, until they are even.)

HighConcentration

LowConcentration

CellMembrane

Glucosemolecules

Proteinchannel

Osmosis•Selectively permeable means that only

some substances can pass through.•Osmosis - is the diffusion of water

through a selectively permeable membrane.

•Water diffuses from an area of high concentration to an area of low concentration.

•Diffusion will stop once equilibrium is reached

•We say a solution has reached equilibrium when there is no “net movement” (substances move back and forth equally).

In comparing the inside of the cell to the solutions on the outside of the cell:

• Isotonic- the solution on the outside has the same concentration of solutes and water as the solution inside the cell, causing the cell to remain unchanged.

• Hypertonic- the solution outside has a HIGHER concentration of solutes (and less water) than the solution inside the cell, causing the cell to lose water and shrink.

• Hypotonic- the solution outside has a LOWER concentration of solutes (and more water) than the solution inside the cell, causing the cell to gain water and swell.

• Pressure is exerted on the hypertonic side

Effects of Solutions on CellsPlant Cells Animal Cells• Plasmolysis - occurs in

plant cells placed in a hypertonic solution for a long period of time. The cell shrivels and pulls away from the cell wall.

• Turgidity – occurs in plant cells placed in a hypotonic solution for a long period of time. The cell swells but does not burst due to the pressure of the cell wall.

• Shriveling – occurs in animal cells placed in a hypertonic solution for a long period of time. The cell can eventually die due to lack of water.

• Lysis – occurs in animal cells placed in a hypotonic solution for a long period of time. The animal cell membrane bursts open and dies due to an excess of water.