diffusion and osmosis - university of california,...
TRANSCRIPT
Diffusion and Osmosis
Selectively Permeable Some substances can
pass through themembrane while othercannot
Why is this important?– Cells must let in
needed materials(oxygen, food) whilegetting rid of wasteproducts.
Diffusion Molecules move from an
area of higherconcentration to anarea of lowerconcentration
What causes diffusion?– Random motion of
molecules2
3
14
WaterDissolvedmolecules
Osmosis Diffusion of water
molecules through aselectively-permeablemembrane– Dissolved molecules
(i.e. glucose, starch)are called solutes
– The liquid they aredissolved in is calledthe solvent
Effects of Osmosis on Cells
[water] = [solute]
Low [water]outside cell
High [water]outside cell
Transportation of Molecules Passive Transport
– Movement of dissolvedmolecules through amembrane WITHOUTusing cellular energy
Active Transport– Movement of molecules
through a membraneUSING cellular energy
Egg-speriment
VinegarSugarsyrup
Distilledwater
Coloredwater Cola
DietCola
Saltwater Alcohol
Demonstrate the effects of osmosis using anegg to model a cell– Dissolve eggshells in vinegar (weak acid)– Submerge eggs in different aqueous environments– Measure volume of liquid remaining and egg
circumference to determine movement of water