We performed a lab that studied osmosis in potato cells. We put cylinders of potato into varying molar Sucrose solutions and after recording different types of data were able to find the osmotic and water potential of the sucrose solution and potato cells.
One of the questions on our lab packets goes as follows:
"Would the water potential of the potato cells change if the cylinders were allowed to dry out? In what way?"
I wasn't sure about the answer, but this is what I wrote. Is it plausible, or am I thinking incorrectly?
Yes, the water potential of the potato cells would change if the cylinders were allowed to dry out. Water potential is defined as the “the potential energy of water relative to pure water in reference conditions”. In other words, water potential describes the tendency of water to move from one place to another. If the cylinders were to dry out, the amount of solute inside the cylinders would remain constant, but the amount of solvent would be reduced to zero (if the potato cylinders were to COMPLETELY dry out). While the amount of solute would stay the same, the concentration of the solute would become infinitesimally high (mol of solute/ (approximately zero L solvent) = infinity). Since water potential is equal to osmotic potential under constant pressure, water potential is largely influenced by the concentration of solute. Since the concentration increased, the water potential would increase as well. This means that if the cylinders were to be put in a water solution, water would rapidly flow into the potato cells in an attempt to equilibrate the solute concentrations inside and outside the cell.
sounds reasonable to me from what I remember in bio but I'm not sure you need the last part if all they are asking is what will happen if the potato cylinders dry out since your above statement is probably adequate.
"This means that if the cylinders were to be put in a water solution, water would rapidly flow into the potato cells in an attempt to equilibrate the solute concentrations inside and outside the cell." => this is the statement that can be included but is more than what they ask.
You used the word "infinitesimally" in an interesting way...
Really had to say that.
Why is the percentage change of each strip calculated but not the actual change?
Well, your answer is technically correct and provides a good explanation of why the water potential of the potato cells would change if they were allowed to dry out. However, let me clown it up a bit for you:
Oh, the poor potato cylinders! If they were allowed to dry out, they would definitely experience a change in water potential. It's like leaving a thirsty clown in a desert with no water gun. When the cylinders dry out, the amount of solvent (water) inside the potato cells would become as scarce as a good joke at a library. The solute concentration would remain the same, but the lack of water would make the concentration explode, like a balloon filled with too much air. This increase in concentration would make the water potential of the potato cells shoot through the roof!
If these dehydrated potato cylinders were placed in a water solution, water would rush into them faster than people running towards free ice cream! It's all about that balancing act, you know? The potato cells would desperately try to reach equilibrium with the lower solute concentration outside. So, in order to rehydrate those poor potato fellows, lots of water would be needed. Just like a clown needs a never-ending supply of water balloons to create laughter!
So, yes, the water potential of the potato cells would definitely change if they were allowed to dry out because of the imbalance in solute concentration compared to the surrounding environment. And we certainly don't want our potatoes feeling like they're stranded in a desert without any water balloon fun!
Your explanation is mostly accurate, but there is a slight technical error in your reasoning.
When you say that "the amount of solute inside the cylinders would remain constant", that is not entirely correct. When the potato cylinders are allowed to dry out, the water inside the cells will evaporate, causing a loss of solvent. As a result, the concentration of solutes within the cells will actually increase.
This means that the water potential of the potato cells would decrease if the cylinders were allowed to dry out. As you mentioned correctly, water potential is influenced by the concentration of solute. Higher solute concentration results in a lower water potential, as water will tend to move from an area of higher water potential to an area of lower water potential.
Therefore, if the cylinders were to be put in a water solution after drying out, water would still flow into the potato cells, but at a slower rate compared to hydrated cells. This is because the water potential of the cells would be lower, and the concentration gradient between the solution and the cells would be less pronounced.
To summarize, the water potential of the potato cells would decrease if the cylinders were allowed to dry out, leading to a slower rate of water uptake when placed in a water solution.