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Need help with water potential

Describe and explain the effects of placing animal and plant cells in solutions of differing solute concentration. For this question, although it asks about solute concentration, the mark scheme mentions nothing of it other than water potential and solute potential. Can anyone elaborate, I am getting confused because I thought that high solute concentration means high solute potential ... Thanks
Original post by coconut64
Describe and explain the effects of placing animal and plant cells in solutions of differing solute concentration. For this question, although it asks about solute concentration, the mark scheme mentions nothing of it other than water potential and solute potential. Can anyone elaborate, I am getting confused because I thought that high solute concentration means high solute potential ... Thanks


This is a broad question so I'm assuming they're expecting you to make a lot of points. The main part of the question is that they want you to describe AND explain the effects of both plant and animal cells, if they come into contact with differing solute concentrations.

First of all, we'll start with animal cells. The question is expecting you to describe what happens if the animal cell comes into contact with a low solute concentration medium, then explain why it has these effects. You'd then to the same describing the nature of an animal cell in a high solute concentration, explaining what happens and why this happens (due to water potential/solute potential). You'd then have to describe the same nature with plant cells. Since the question states "differing solute concentrations", this means it wants to know how the cells react specifically relating to the water/solute potentials.

That's just explaining the question and how they expect you to answer it. Quote me if you need help with your answer :smile:
Reply 2
Original post by Eloades11
This is a broad question so I'm assuming they're expecting you to make a lot of points. The main part of the question is that they want you to describe AND explain the effects of both plant and animal cells, if they come into contact with differing solute concentrations.

First of all, we'll start with animal cells. The question is expecting you to describe what happens if the animal cell comes into contact with a low solute concentration medium, then explain why it has these effects. You'd then to the same describing the nature of an animal cell in a high solute concentration, explaining what happens and why this happens (due to water potential/solute potential). You'd then have to describe the same nature with plant cells. Since the question states "differing solute concentrations", this means it wants to know how the cells react specifically relating to the water/solute potentials.

That's just explaining the question and how they expect you to answer it. Quote me if you need help with your answer :smile:


Hi, thanks for replying. This is what I have mentioned in my answer but it is wrong.
-Incipient plasmolysis and plasmolysis take place when the external solution is hypotonic to the plants cells, causing water to move out of the cell.
-Animal cells will burst when placed in a solution with low solution concentration. (Would this be hypo or hypertonic? )
- Animal cells will shrink and become crenated in a solution that has high solute concentration. The bit about the solute concentration is wrong but I don't understand why. Thanks
(edited 8 years ago)
Reply 3
Original post by coconut64
Hi, thanks for replying. This is what I have mentioned in my answer but it is wrong.
-Incipient plasmolysis and plasmolysis take place when the external solution is hypotonic to the plants cells, causing water to move out of the cell.
-Animal cells will burst when placed in a solution with low solution concentration. (Would this be hypo or hypertonic? )
- Animal cells will shrink and become crenated in a solution that is high solute concentration. The bit about the solute concentration is wrong but I don't understand why. Thanks


A high solute concentration means a lower water potential. Pure water has the highest water potential of 0 kPa. Values of water potential are negative, so the higher the solute concentration the more negative the water potential.

A hypotonic solution is one where the water potential inside the cell is lower than the water potential outside of the cell. This will cause water inside the cell to move into the cell by osmosis (from high to low water potential) causing animal cells to swell and eventually lyse and plant cells to become turgid.
A hypertonic solution is one where the water potential inside the cell is greater than the water potential outside the cell, which causes water outside the cell to rush into the cell by osmosis (from high to low water potential) causing animal cells to crenate and plant cells to become plasmolysed.
An isotonic solution is one where the water potential inside and outside the cell are the same, hence there is no water potential gradient and so there is no net movement of water into or out of the cell.
Reply 4
The more solutes there are, the more negative the solute potential becomes and more negative water potential becomes.

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