Passive Transport

Passive Transport

• does not utilize cellular energy

• molecules move from areas of high concentration to areas of low concentration until equilibrium is met

• Examples- simple diffusion, osmosis, facilitated diffusion

Factors that can affect diffusion

• pressure

• mixing

• temperature

• particle size

• particle concentration 

simple diffusion

movement of molecules down their concentration gradient

osmosis

• movement of water from areas of high water concentration to areas of low concentration

• water travels through channel proteins called aquaporins

• water movement is affected by solute concentration on either side of the membrane

Tonicity

• the concentration of water relative the cell

Hypotonic

• low solute/ more water

Ex: distilled water

Result- cells will gain water when played in solution 

Water enters the cell

animal cell: burst/ lyse

Plant cells: turgid pressure 

Hypertonic

• more solute/less water

Ex:saline 

Result: cells will loose water when played in this solution

Water leaves the cell

Animal: shriveled

Plant: plasmolyzed (cell membrane shrinks)

Isotonic

• Solute concentration is equal on either side of the membrane

• Result: cell stays in equilibrium 

Water enters and leaves the cell

Animal cell-normal

plant cell- wilt or is flaccid

Facilitated Diffusion

• A transport protein that helps materials through the cell membrane.

• Doesn't require energy (ATP).

• Works on a downhill concentration gradient.