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Re: Aquatic Plants Digest V4 #26

>On Wed, 12 Jan 2000, George Booth wrote:
>> Your fish are going to get stressed only if CO2 increases TOO much
>> overnight or the O2 is reduced TOO much overnight. Even with high
>> oxygen levels, fish cannot respire CO2 unless the concentration of CO2
>> in the water is less than the concentration of CO2 in the fishes
>> blood. The exchange of O2 and CO2 in the gills is determined by the
>> relative concentration of each gas on both sides of the gill membrane
>> and the exchange of each gas at the membrane is independent of the
>> other.
>> Many people miss this point. With high O2 AND high CO2 in the water,
>> CO2 cannot leave the blood (meaning O2 can't enter the blood; they
>> bind to the same site on the hemoglobin molecule) and the animal
>> asphyxiates. With low O2 AND low CO2 in the water, CO2 can leave the
>> blood but O2 can't enter and the animal asphyxiates.

No, no, no -- you've forgotten about active transport, which is one way an
organism achieves higher concentrations of the desired material (some
gasses, e.g. O2, & some other molecules) inside the cell than outside, and
lower concentrations of unwanted materials inside than outside. 

back to lurking,
Genetics Major
Texas A&M University