Transcript Osmosis and Diffusion

Cell Transportation
How substances moves in and out of
cells
Review: Cell Membrane
Function

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Protects the cell
Takes in food/nutrients
Gets rid of waste from inside cell
Allows cells to communicate w/ other
cells
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Cell Membrane Structure
 A semipermeable
membrane
 Lipid molecules
form a double
layer
 protein
molecules can
move around
inside layer
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The cell membrane in an
animal cell:
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The cell membrane in a plant
cell:
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Diffusion
 Movement of molecules
across a membrane
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 Molecules move from areas
of high concentration to
areas of low concentration
 high concentration=more
molecules; low
concentration=less
molecules
Diffusion in Cells
 Not all molecules can
move across the cell
membrane by diffusion
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 Rules:
1.) equal # of molecules on
both sides
2.) molecules move in or out
of cell until there is an
equal # on both sides of
the cell membrane
Osmosis
 Movement of water
molecules across a
membrane
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 Like diffusion,
molecules move
from an area of
high concentration
to an area of low
concentration.
Osmosis in Cells
 Rules: 1.) H20 can pass across the cell
membrane in both directions
2.) amount of H20 going in=same
amount of H20 going out
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Three different types of environments
for the cell membrane
 Isotonic Solution: The water
concentration is the same as that of the cell.
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Three different types of environments
for the cell membrane
 Hypertonic Solution: has a lower
concentration of water compared to the cell.
 Water goes out of the cell, causing it to
shrivel.
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Three different types of environments
for the cell membrane
 Hypotonic Solution: has higher
concentration of water as compared to that of
a cell.
 The water pushes into the cell, causing the
cell to swell-up.
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Three different types of
environments for the cell
membrane
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Blood Cells in different solutions
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Passive Transport
 Movement of molecules across a cell
membrane
 Another way of saying ‘osmosis and
diffusion’
 Does not require energy
Active Transport
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ATP=chemical
energy used
For pump!
 Process that allows
molecules to move
across the cell
membrane from lower
to high concentrations
(opposite of diffusion!)
 Active transport
requires energy in the
form of proteins as
they “pump” to move
molecules across the
cell membrane.
Passive v. Active…let’s compare!
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Protein Channels
 Larger molecules (i.e. sugars) need help getting
through membrane; transported through protein
channels
 Does not require energy b/c the molecules are
still moving from areas of higher concentration to
areas of lower concentration.
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