How can we accurately measure osmosis in a cell?

[alexandria]

Homework Statement

Hi, I'm doing a biology course online and I'm specifically learning biochemistry right now. I'm having a problem with the following question related to one type of passive transport in a cell: this being osmosis. This question relates to measuing osmosis (isotonic, hypertonic, and hypotonic categorizations)

Homework Equations

none

The Attempt at a Solution

Here are my attempted answers, please correct me if I'm wrong, thanks in advance!
Also, I read some answers online for part b), and apparently the beaker that contains the distilled water is beaker B, so I'm not sure if i did part b) of this question correctly?? Any help would be appreciated :)

 

[DrClaude]

I think that your answer is correct. The only thing I would change is that I would not use the expression "water concentration." Water is the solvent here, so it makes no sense to talk about it's concentration. You could maybe use water potential instead..

 

[Borek]

Water is the solvent here, so it makes no sense to talk about it's concentration.

Sounds a bit strange perhaps, but I see nothing intrinsically wrong with the idea. Pure water has a molar concentration of 55.56 mol/L.

 

[DrClaude]

Sounds a bit strange perhaps, but I see nothing intrinsically wrong with the idea. Pure water has a molar concentration of 55.56 mol/L.

I never heard anything like that, but you have a greater experience of this than I do. So @alexandria, you can forget my comment. What you wrote is fine.

 

[alexandria]

I used the term 'water concentration' because they explained it in the lesson that way:
so should i change it to 'water potential' by saying "area of higher water potential to an area of lower water potential"?
Here is what was written in my lesson:

so for part b) is my answer correct? does beaker A actually contain the distilled water and does my explanation make sense?

 

[Empirical Wizardry]

(1) Hi Alexandria, good answer for part (b)! Have a look at the water level in the container as well; how is the change in the container compared to the osmometer? Why do you think it's important to keep track of where all the water in the system goes before we say anything further?

(2) The term 'water potential' was suggested rather than 'water concentration'. Water potential is a more general and safe term that does not presuppose any mechanism, only a free energy difference between the compartments, so it is why it is preferred.

Understanding osmosis as movement of water from a lower concentration to a higher concentration provides an intuitive and usually correct understanding of osmosis, so usually it is not an issue. However this supposes a mechanism for the movement of water. If this mechanism is wrong, then our understanding of osmosis and the predictions we make from the model will be wrong for certain cases.

So does osmosis work as the result of a water concentration gradient? As a scientist it's important to look at how to prove something wrong rather than right. The hypothesis is that water will move from a region of higher concentration of water molecules to a lower concentration of water molecules. What observation would we have to see to refute the water concentration hypothesis? Has anyone else tried to test this hypothesis before (try a google search)? If they have, what are their results?