Biology – Movement into and out of cells | e-Consult

Experimental Procedure:

1. Prepare a series of sucrose solutions of known concentrations (e.g., 0 M, 0.2 M, 0.4 M, 0.6 M, 0.8 M). Ensure the solutions are at the same temperature.
2. Cut potato cylinders of equal length and diameter.
3. Weigh the potato cylinders and record the initial mass.
4. Immerse the potato cylinders in each sucrose solution for a fixed time period (e.g., 24 hours).
5. After the immersion period, remove the cylinders from the solutions and carefully pat them dry to remove any excess solution.
6. Weigh the potato cylinders again and record the final mass.

Variables to Control:

• Length and diameter of potato cylinders
• Temperature of sucrose solutions
• Immersion time
• Volume of sucrose solution used for each cylinder

Variables to Measure:

• Initial mass of potato cylinders
• Final mass of potato cylinders

Estimating Water Potential: The student can use the mass change to estimate the water potential. The mass change is proportional to the difference in water potential between the potato tissue and the surrounding solution. A higher mass gain indicates a lower water potential in the potato tissue, and vice versa. A graph of mass change versus sucrose concentration can then be plotted to determine the relationship. The water potential can be estimated from the gradient of this graph.