October 19, 2012.
Diffusion – The process by which molecules of
a substance move from areas of higher
concentration to areas of lower
concentration.
DOES NOT REQUIRE ENERGY!
Because diffusion depends upon random
particle movements, substances diffuse
across membranes with out requiring the cell
to use energy.
Dialysis tubing example
o Tie 1 end
o Add scoop of starch and some water
o Tie other end and rinse bag, place in beaker
o Add 2-3 full droppers of iodine to beaker
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Osmosis is the diffusion of water molecules
across a membrane
No energy is required (diffusion does not use
energy)
Molecules move from areas of higher to lower
concentration
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The concentration of molecules in solution
outside of a cell influences osmosis.
Isotonic solution – means there are equal
amounts of the molecule inside and outside
of cell.
Hypertonic solution – means there are more
molecules outside the cell than inside.
Hypotonic solution- means there are less
molecules outside the cell than inside.
If the
solution
outside of
the cell is:
Then the water
inside the cell will:
Only
LEAVE
Enter and
Leave
Only
ENTER
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A type diffusion where large molecules move
into a cell by passing through a carrier
protein.
Glucose (monosaccharide) travels by
facilitated diffusion into & out of cells.
Definition- movement of materials in the
opposite direction – against a concentration
gradient.
REQUIRES ENERGY!
(Active art from book)
Types
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
Endocytosis
Extocytosis
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Process by which a cell takes material into the
cell by infolding of the cell membrane
Example is phagocytosis
a food particle is surrounded by
phospholipids, creating a vacuole
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Process by which a cell releases large
amounts of material
Example is large amount of water or cellular
wastes being released.