Transport - Research Article from Macmillan Science Library: Animal Sciences

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Osmosis

The simplest kind of cellular transport is osmosis. Osmosis is the passage of water molecules through a semipermeable membrane from a wet environment (a region of high water concentration), to a dry environment (a region of low water concentration). The defining characteristic of a wet environment is a low concentration of dissolved solute in the water. A dry environment has a high concentration of solute. Cells store a high concentration of proteins and other molecules within the membrane. If a cell were removed from biological conditions and placed in distilled water (water containing no dissolved substances), the small water molecules would rush through the bilipid membrane into the relatively dry interior of the cell. The membrane would expand with the increased water intake until the cell exploded.

This scenario does not normally occur in nature for two reasons. First, organisms balance their internal osmolarity. Internal osmolarity is the...

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This section contains 1,726 words
(approx. 6 pages at 300 words per page)
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Macmillan Science Library: Animal Sciences
Transport from Macmillan Science Library: Animal Sciences. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.
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