Transcript Diffusion

Diffusion
•Particles naturally travel from areas where they are crowded
to areas where they are less crowded.
http://www.indiana.edu/~phys215/lecture/lecnotes/lecgraphics/diffusion.gif
•Diffusion is the movement of particles from an area
where their concentration is high to an area where their
concentration is low.
Osmosis
• All living organisms
depend on water
• Living cells are
surrounded by and filled
with fluid that is made up
mostly of water
• The diffusion of water
across a cell membrane
is so important to life
processes that it has
been given a special
name – osmosis.
http://www.himalayancrystalsalt.com/wellness/osmosis.gif
*Checkpoint*
 What would happen to a grape if you placed in a dish full of pure water?
 What would happen to a grape if you placed it in water mixed with a large
amount of sugar?
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http://www.ndpteachers.org/perit/osmosis2.gif
Moving Small Particles
 Some particles (such as
water and oxygen) are small
enough to diffuse directly
through the cell membrane
 Others (such as sugar and
amino acids) are too large to
squeeze through the
membrane and require
protein “doorways” in order to
enter or leave the cell.
http://fig.cox.miami.edu/~cmallery/150/memb/c8x16types-transport.jpg
Passive Transport
 Passive transport is the diffusion of particles through proteins.
 These particles move from an area of high concentration to an area of
low concentration.
 Requires NO ENERGY
http://discover.edventures.com/images/termlib/p/passive_transport/support.gif
Active Transport
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Active transport is the movement of particles through proteins against the
normal direction of diffusion.
Particles are moved from an area of low concentration to an area of high
concentration
Requires ATP
Moving Large Particles
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Endocytosis
Means “within the cell”
Cell membrane surrounds a particle and once the particle is completely
surrounded, the vesicle pinches off and enters the cell.
http://jan.ucc.nau.edu/~lrm22/lessons/endocytosis/endocytosis.gif
Moving Large Particles
 Exocytosis
 Vesicles inside the cell travel to the cell membrane and fuse with it to
release the particles.
http://upload.wikimedia.org/wikipedia/commons/thumb/1/16/Exocytosis_types.svg/399pxExocytosis_types.svg.png