Transcript 2-7 Diffusion

2-7 Diffusion
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Molecules

Molecules are the smallest part of a
substance that still have the
characteristics of that substance.

Molecules are always moving
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Diffusion is..

Movement of material from an area where
molecules are crowded to an area where
they are less crowded.

http://commons.wikimedia.org/wiki/File:Diff
usion.gif
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Passive Transport

Is diffusion through cell membranes

http://www.bio.miami.edu/~cmallery/150/m
emb/c8.7x11.diffusion.jpg
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OSMOSIS
Osmosis is the movement of water
molecules through a membrane
 Many substances dissolve in water.
 Water plus the dissolve substance move
through the cell membrane
http://www.stjohn.ac.th/Department/school/bi
o_pix/osmosis.gif

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What do you think?

What would happen if water constantly
entered a cell, and none left it?
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It will burst
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Active Transport
The cell may need more of a substance
inside the cell than outside.
 This requires molecules to move in the
opposite direction they would normally
move.
 Energy is required for molecules to move
from less crowded to more crowded areas.
 http://www.biology4kids.com/files/art/cell2_
active1_240x180.gif

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