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## AP®︎/College Biology

### Course: AP®︎/College Biology>Unit 2

Lesson 7: Mechanisms of transport: tonicity and osmoregulation

# Mechanisms of transport: tonicity and osmoregulation

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## Problem

A group of biology students weighed several potato cubes and placed them in open beakers containing various sucrose solutions at ${30}^{\circ }\text{C}$. The following day, the students weighed the potato cubes again and calculated the differences in mass.
It was determined that solute potential equilibrium was reached at $0.35\phantom{\rule{0.167em}{0ex}}\text{M}$.
Solute potential of a solution: ${\psi }_{s}=-iCRT$
• $i=$ ionization constant ($1.0$ for sucrose)
• $C=$ molar concentration
• $R=$ pressure constant ($0.0831\phantom{\rule{0.167em}{0ex}}\text{L}\cdot \text{bar}\cdot {\text{mol}}^{-1}\cdot {\text{K}}^{-1}$)
• $T=$ temperature in Kelvin (${}^{\circ }\text{C}$ of solution $+\phantom{\rule{0.167em}{0ex}}273$)
What is the solute potential of the potato cubes?