Osmotic pressure

[brood910]

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In hypotonic solution, as water enters the cell, I thought osmotic pressure will increase, in order to resist the flow of water. But, TPRH says the otherwise. It says "even though osmotic pressure inside the cell is high, after water flows in, it decreases." Why is this? Are they talking about AFTER the water FINISHED flowing in?

 

[pjk77]

i think you might be confusing osmotic pressure and hydrostatic pressure
osmotic pressure is the difference due to solute concentrations and is high when there is a big difference in solute concentrations. thus, as the solute concentrations become more at equilibrium and more similar, osmotic pressure (due to a difference in solute concentrations) is going to go down to zero.
Hydrostatic pressure- which is the outward pressure due to water would increase opposite to osmotic pressure. So it would increase as water enters the cell, but it would just go from negative to zero. if the water becomes greater inside the cell, then hydrostatic pressure could be positive to force it out.

in summary, osmotic pressure draws water in; hydrostatic forces it out.

 

[Lifeman]

Think of osmotic pressure as the hydrostatic pressure that a column of water can support through a semipermeable membrane.

 

[brood910]

"When two solutions having different solute concentrations are divided by a semi permeable membrane, the solvent at the low concentrated side tends to move to the high concentration side. Imagine a balloon made of the semi permeable membrane filled with high concentration solution submerged inside the low concentrated solvent. The solvent will transfer to the inside of the membrane. This will cause the pressure of the inside of the membrane to rise. This risen pressure is known as the osmotic pressure of the system. This is a vital mechanism in transferring water to the inside of the cells. Without this mechanism, even trees cannot survive. The inverse of osmotic pressure is known as water potential, which is the tendency of the solvent to stay in the solution. Higher the osmotic pressure, lower will be the water potential."

http://www.differencebetween.com/di...essure-and-vs-osmotic-pressure/#ixzz2qXeAf4pW"

Other places including this website says the otherwise tho..
They are saying that osmotic pressure increases as water enters..

I am even more confused now wtf..

 

[TheVitalReview]

that's a pretty confusing explanation that you found there.

Osmotic pressure is the pressure that is created because of the DIFFERENCE in concentration between two solutions on opposite sides of a membrane. So if you have water flowing from one side of the membrane to the other to balance out concentrations, the DIFFERENCE in concentration goes down, so your osmotic pressure will go down as well.

here's a 1 minute animation that might make the process a little more clear:

 

[pjk77]

yeah don't read that differencebetween.com website.. thats just not accurate.