Transcript Document

Passive Transport
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Passive Transport: Movement of
materials across the membrane that
does not require energy
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Types:
Diffusion
Osmosis
Facilitated Diffusion
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Diffusion is the
movement of
molecules from an
area of high
concentration to
an area of lower
concentration until
they are evenly
spread out
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Factors that determine whether
diffusion occurs across a
membrane are
concentration gradient
and
permeability
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Diffusion occurs across a “concentration
gradient” which is the difference between
the concentration of a particular substance in
one area and the concentration in an adjacent
area
Concentration Gradient
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Permeability is the ability of a substance to
pass through the membrane
Biological membranes are
selectively permeable or
semi-permeable and only
allow certain molecules to
pass through freely by
diffusion
Osmosis is the diffusion of water molecules through
a selectively permeable membrane
Water will continue to diffuse/move until there are
equal numbers of molecules inside and outside the
cell. Animation: How OSMOSIS works
hypotonic
isotonic
hypertonic
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Hypertonic Solutions
• Solute concentration outside of the cell is
higher than the solute concentration inside
the cell
• Water moves OUT of the cell
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Hypotonic Solutions
• Solute concentration outside of the cell is
lower than the solute concentration inside
the cell
• Water moves INTO the cell
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Isotonic Solution
• Solute concentration in the solution is equal
to the solute concentration in the cell
• Water moves equally in and out of the cell
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Which way will the water move?
On the left side,
more of the space
is occupied by
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solutes than by
water
60% H2O
90% H2O
Which way will the
water move?
80% H2O
100% H2O
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What type of solution is
this cell in?
80% H2O
100% H2O
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Which way will
the water move?
90% H2O
90% H2O
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90% H2O
What type of
solution is this
cell in?
90% H2O
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Which way will the
water move?
90% H2O
75% H2O
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What type of
solution is this cell
in?
90% H2O
75% H2O
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Some things like glucose and proteins are
too large to pass though the membrane by
diffusion or osmosis
Carrier proteins
transport (diffuse)
large substances
across the
membrane from
high to low
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concentration