Old 09-30-08, 11:38 PM
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Originally Posted by fuzzbox View Post
Well, the long answer is that animal cells have membranes surrounding them that are both hydrophilic (at the "heads") and hydrophobic (at the "tails"). This allows an easy or passive distribution of hydrophobic molecules through the membrane (things like Oxygen and Carbon Dioxide) but prevents hydrophilic molecules to pass through (like water). The reason for the cell doing this is that Oxygen and Carbon Dioxide must pass quickly through the cell, but the cell needs to be more restrictive about the other substances it lets in.
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