The Movement of Materials Across a Cell Membrane

The Movement of Materials Across a Cell Membrane

Which materials must get into/out of a cell? IN • • Food Water O 2 (animal cell) CO 2 (plant cell) OUT Wastes • CO 2 (animal cell) • O 2 (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

Diffusion (cont. )

Ex: The diffusion of CO 2 across a cell membrane CO 2 water

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

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

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