Osmotic pressure versus osmotic potential

[reising1]

A few questions:

1. Is Osmotic potential the same as Osmotic pressure?
2. I know that water travels from hypotonic (high pressure) to hypertonic (low pressure) solutions. Does this mean that the more solute, the lower the osmotic pressure? Is this also true for osmotic potential?

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[dcamkl1]

They are different things.

Picture a tank of water, divided into two compartments by a semipermeable membrane. One the left is just pure H2O, on the right you had a bunch of salt, or some other solute. As you mentioned, the water on the left (hypotonic) will flow into the right, which is hypertonic.

The compartment on the right will have a higher osmotic pressure (pi = mirt), which is defined as the pressure needed to resist the flow of water into it.

The compartment on the left has a higher osmotic potential, because the definition of osmotic potential is the measure of a solution's "potential" to move to a hypertonic solution. The pure water on the left has a bigger potential to flow to the right; the salt solution on the right has a negative potential to move to the left. A tank of just pure water has an osmotic potential of zero.

 

[reising1]

They are different things.

Picture a tank of water, divided into two compartments by a semipermeable membrane. One the left is just pure H2O, on the right you had a bunch of salt, or some other solute. As you mentioned, the water on the left (hypotonic) will flow into the right, which is hypertonic.

The compartment on the right will have a higher osmotic pressure (pi = mirt), which is defined as the pressure needed to resist the flow of water into it.

The compartment on the left has a higher osmotic potential, because the definition of osmotic potential is the measure of a solution's "potential" to move to a hypertonic solution. The pure water on the left has a bigger potential to flow to the right; the salt solution on the right has a negative potential to move to the left. A tank of just pure water has an osmotic potential of zero.

Why would the compartment on the right have a higher osmotic pressure? Balance says that high pressure wants to flow to low pressure. In this case, the left flows to the right, so the left should have the higher pressure.

Are you saying that with osmotic pressure, low pressure wants to flow to high pressure??

 

[krogers21]

Why would the compartment on the right have a higher osmotic pressure? Balance says that high pressure wants to flow to low pressure. In this case, the left flows to the right, so the left should have the higher pressure.

Are you saying that with osmotic pressure, low pressure wants to flow to high pressure??

The right side has a higher osmotic pressure because water wants to flow into the right side whereas osmotic pressure is the pressure trying to oppose this transfer of water into the right side. Make sense?


Also, the pressure the water is exerting on the higher concentration is the hydrostatic pressure(the fluid essentially trying to create equilibrium).

 

[reising1]

Okay, so more solute means higher osmotic pressure and lower osmotic potential?

 

[hamsawx]

seems like it could be related to gravitational potential. something at a high gravitational potential (10 meters in height) will want to fall towards a low gravitational potential (ground level). So high osmotic pressure on the right side, which is where the solvent (water) wants to "fall," cause the water to "fall" towards a lower osmotic potential from a higher osmotic potential.