Transcript Diffusion and Osmosis Power Point

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The CM determines what
gets in and out of cells.
Some molecules pass
through easily including
lipids that dissolve in the
lipid layer of the CM.
Small molecules such as
water, glucose and
amino acids also pass
through easily.
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Some molecules do not
pass through easily
including large
molecules (starch,
protein) and those that
carry charges (attract to
opposite charge on CM).
How cells move
substances across the
cell membrane involves a
number of different
processes.
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Molecules of liquids and gases are always
in motion. These molecules collide with
each other,and thus undergo diffusion.
Diffusion: Movement of molecules from an
area of high concentration, to one of low
concentration(Ex. Perfume,coffee)
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The difference in concentration between a
region of greater concentration and a
region of lesser concentration is called a
concentration gradient (shown below).
Low O2 level
High CO2 level
High O2 level
Low CO2 level
Movement of gases in cellular respiration
involves concentration gradients.Note the direction
of movement from high to low.
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Click here for animation.
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This is a “fast” form of diffusion.
Molecules get some help crossing the
membrane.
Evidence shows that there are proteins in the
cell membrane with hollow channels.
Molecules pass through these channels along
a concentration gradient.
Animation
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This is another way to move materials into
and out of cells.
In this case the cell must use energy to move
substances against a concentration gradient.
This allows the cell to maintain internal
conditions that are chemically different from
the external environment.
Animation
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Osmosis is a type of diffusion.
In this case, water moves across a
semipermeable membrane from an area of
high water concentration to one of low water
concentration.
Animation
Name
Diffusion
Facilitated
Diffusion
Osmosis
Type of
Transport
Passive
Passive
passive
Direction of
Movement
Conditions
Examples
towards
lower
concentrati
on
Concentrati
on gradient
Water,
gases
(02and
CO2), and
steroid
hormones.
towards
lower
concentrati
on
Concentrati
on
gradient,
plus
channel or
carrier
proteins
Water,
glucose,
and amino
acids.
towards
lower
concentrati
on
Concentrati
on
gradient,
channel
proteins
optional
Water 0nly.
towards
Ions,