The Movement of Materials Across a Cell Membrane

Which materials must get into/out of a cell? Food Water O2 (animal cell) CO2 (plant cell) Wastes CO2 (animal cell) O2 (plant cell) excess water

How do materials get into/out of a cell? DIFFUSION The tendency for very small molecules to drift from where they are in greater concentration toward where they are in lesser concentration Ex: perfume molecules diffusing across a room diffusion “stops” when the concentrations equalize -

Diffusion (cont.)

Ex: The diffusion of CO2 across a cell membrane water

- Osmosis is a special kind of diffusion - the diffusion of water molecules across a cell membrane - the laws of diffusion apply -

cell swells cell shrivels cell stays same cell in pure water hypotonic solution contains less dissolved substances than a cell does hypertonic solution contains more dissolved substances than a cell does isotonic solution contains the same concentration of dissolved substances as a cell 100% 70% 50% 70% 70% 70% cell in pure water cell in 50% water (50% salt) solution cell in 70% water (30% salt) solution cell swells cell shrivels cell stays same

Osmosis animation

QUIZ

1 & 2 List two things that must constantly enter a plant cell in order for it to stay alive.

- 3 - Besides the general term “waste”, name one thing that must constantly EXIT a plant cell in order for it to stay alive.

- 4 - Osmosis Diffusion Hypotonic Isotonic Hypertonic Which term refers to the tendency for very small molecules to drift from one place to another because of their relative concentrations?

What will happen to this cell? - 5 - What will happen to this cell? Shrink Swell Stay the same 70% 90% cell in 90% water cell will swell