when does osmosis stop

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Feb 12, 2018
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I have a question about osmosis that goes a bit deeper than most basic textbooks so I cannot find the answer.Here's the problem:

Imagine an animal cell, say a red blood cell, in a slightly hypotonic solution. The water starts to flow in osmotically. The concentration of solute in the cell decreases. The cell slowly starts to swell but does not burst.

The question is: Does this water entering increases the pressure on the membrane (similar to turgor in plant cells only less, because the cell can increase in volume - comparable to elastic energy that must be overcome when blowing a baloon...) and does this cause osmosis to stop BEFORE the concentrations come to equilibrum (meaning that cytoplasm still has a bit more solute concentration than outside of cell) or do the concentrations perfectly match?

Thanx in advance.

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OldCloner 11 months ago

Yeah, this is a thinker. It probably depends on the nature of the solute and whether or not it can freely cross the membrane. If it can, some of what is in the cell can come out and a true equilibrium can be reached. If not, probably your scenario with the cell membrane holding back expansion before equilibrium is reached could occur. Anybody else have any ideas? I haven’t reviewed osmosis in AGES!