February 26, 2017

Homework Help: Ap Biology

Posted by Jessie on Saturday, November 24, 2007 at 8:46pm.

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.

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