Osmosis and Salt Concentration

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Osmosis in Plant Cells
Sara Braqi
March 25, 2012
Biology I

Research Question
Which saltwater concentration will have the most damaging effects on potato cells? Introduction
Osmosis is the diffusion of water across a selectively permeable membrane. Generally, water moves from a lower solute concentration into a higher solute concentration. This movement of water occurs due to the need for the concentrations in the cell and in the solution to be at equilibrium. A solution with a low solute concentration and a high water concentration is referred to as hypotonic. A solution with a high solute concentration and a low water concentration is referred to as hypertonic. When two solutions are isotonic, there is no net flow of water because the solutions have equal concentrations. When a cell is put into a hypertonic solution, it will lose water and plasmolysis- shrinking of the cytoplasm- may occur in plant cells. Without this water there is little pressure inside the cells and the plant can no longer support itself against the pull of gravity. When a cell is put in a hypotonic solution, it will gain water and become turgid, or swollen. In plant cells, this is the state in which the concentrations are balanced due to the wall pushing back on the cell and the plant is strongest. When they are in a hypotonic solution, the cells become inflated with water and the plant stands upright and is able to overcome the pull of gravity. Aim

The aim of this experiment is to find out which saltwater concentration is most hurtful to potato cells and use this model to see how saltwater affects plants in general.

Hypothesis
The highest salt concentration (15%) will have the most damaging effects on the potato cells. Due to the solution’s high solute concentration and low water concentration, water will move into it and out of the cell, causing the cell to become plasmolyzed and weak. Control: the mass of each potato cylinder before it is put in any of the solutions. Independent variable: the solutions of varying salt concentrations. Dependent variable: the mass of each potato cylinder after it is put into the different solutions. Materials and Methods

Materials for Saltwater Solutions
1. Table salt
2. Tap water
3. 4 Beakers
4. Pan
5. Wooden spoon
6. Teaspoon
7. Bunsen burner/ stove top
8. Graduated cylinder
Procedure for Saltwater Solutions
1. Heat up 100 ml of tap water in a pan above room temperature, but do not boil. 2. After the water is heated up, turn off the fire and start adding salt with a teaspoon. Stir the water with a wooden spoon as you sprinkle in the salt. Keep observing the water as it is being stirred. 3. When the water approaches 100% concentration, the salt crystals will no longer dissolve and they will remain whirling around in the water. Let it sit for a few seconds and then check to see if the crystals can still be seen. 4. If they have dissolved, then add more salt until they remain sitting at the bottom of the pan, at which point the solution is 100% saturated and can't dissolve any more salt crystals. 5. Let the water cool to room temperature.

6. After it reaches room temperature, carefully pour the liquid into a beaker labeled “100% salt concentration”. Do not allow the remaining salt crystals to go into the beaker. 7. Label another beaker “10 % salt concentration.”

8. To make the 10% salt concentration, pour 100 ml of tap water into the beaker. Then pour 10 ml of the 100% salt concentration into the same beaker. 9. Label another beaker “13 % salt concentration.”

10. To make the 13% salt concentration, pour 100 ml of tap water into the beaker. Then pour 13 ml of the 100% salt concentration into the same beaker. 11. Label another beaker “15 % salt concentration.”

12. To make the 15% salt concentration, pour 100 ml of tap water into the beaker. Then pour 15 ml of the 100% salt concentration into the same beaker. Materials...
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