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
Phospholipids
Membrane Proteins

Maintains fluidity in the membrane!!! (think
about the cotton plant!)

Maintains
shape, act as
enzymes,
transport
in/out of cell,
cell
communication
(receptors)
Animation: Membrane Selectivity
Right click on animation / Click play
© 2012 Pearson Education, Inc.
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Only small, non-polar molecules move through
the bilayer (ex: O2, CO2, H2O, LipidHormones, Fatty Acids)
**Ionic, Charged, Large, Polar (hydrophilic)
molecules CANNOT cross the membrane
without help!)**


Inactive structural supports composed of
polysaccharides
Plants (cellulose), Fungi (chitin), Many
Prokaryotic cells (peptidoglycan)
Molecules of dye
Membrane
Pores
Net diffusion
Net diffusion
Equilibrium
Net diffusion
Net diffusion
Equilibrium
Net diffusion
Net diffusion
Equilibrium
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Measurement of the relative concentrations of
solute between two solutions (inside and
outside of cell)
Hypertonic – More solute/less solvent
Hypotonic: Less solute/More solvent
Isotonic: Equal concentrations
**These terms are COMPARATIVE**
Lower
Higher
concentration concentration
of solute
of solute
Equal
concentrations
of solute
H2O
Solute
molecule
Selectively
permeable
membrane
Water
molecule
Solute molecule
with cluster of
water molecules
Osmosis