A shipwrecked sailor is stranded on a small desert island with no fresh water to drink. She knows she could last without food for up to a month, but if she didn't have water to drink she would be dead within a week. Hoping to postpone the inevitable, her thirst drove her to drink the salty seawater. She was dead in two days. Why do you think drinking seawater killed the sailor faster than not drinking any water at all? Today we explore the cause of the sailor's death. We'll prepare solutions of salt water to represent the sea, and we'll cut up slices of potato to represent the sailor. Potatoes are made of cells, as is the sailor!
The concentration of solute in a solution will affect the movement of water across potato cell membranes.
potato, corer, 3 plastic cups, marker, salt, sugar, distilled water, paper, pencil, electronic balance, clock with second hand or timer, metric ruler, small ziplock plastic bag, foil or plastic wrap
Results of Osmosis in Potato Cells
|Change in length
(flaccid or crisp)
(flaccid or crisp)
(iso-, hypo-, or hpertonic)
Results & Conclusions:
1. Did any of the potato cylinders change in their turgidity (flexibility), and if so, which ones changed?
2. Explain why the flexibility of the potato slices changed.
3. Define isotonic, hypotonic, & hypertonic solutions.
4. If potato slices changed in length or turgidity, what process was responsible for this?
5. Make a sketch of your potato cylinder in the distilled water and use arrows to show the direction of water movement across the potato cell membranes.
6. What type of solutions were the salt & sugar solutions. Explain how you know this.
7. Which solution served as the control for this experiment & why?
8. In which solutions was their a greater solute concentration outside of the cells?
9. In which direction did water move through these cell membranes?
10. In what type of solution do plant cells do best & why?
11. Using the information you've discovered from this experiment, explain why the sailor died that drank saltwater.