Osmosis And Diffusion

Osmosis In Living Cells

In animal cells, the movement pf water inot an out of the cell is influenced by the relative concentration of solute on either side of the cell membrane. If water moves out of the cell, the cell will shrink. If water moves into the cell, the cell may swell or burst. In plant cells, the presence of a cell wall prevents the cells from bursting, but pressure does eventually build up inside the cell and the cell can resist the influx of water building up turgor pressure. When the pressure inside the cell becomes large enough, no additional water will accumulate in the cell even though the cell still has a higher solute concentration than does pure water. So movement of water through the plant tissue cannot be predicted simply through knowing the relative solute concentrations on either side of the plant cell wall. Instead, the concept of water potential is used to predict the direction in which water will diffuse through living plant tissues.

Procedure:

1. Slice a potato so that the segment is 3cm in height. Using the potato corer, punch out 3 cores for each of the 6 molar solutions. You should have 18 potato cores.

2. Make sure that all 18 cores are the same size. Dry the cores in a paper towel mass all 3 cores together at once and record the initial mass in the data table.

3. Pour 100 mL of each of the solutions into plastic cups.

4. Place the potato cylinders into the cups and let them soak overnight

5. After 24 hours have passed, remove the potato cylinders from the cups and carefully blot off any excess solution with a paper towel.

6. Determine the mass of the 3 potato cylinders and record the final mass in the data table

Discussion and Conclusions:

Claim: When a cell is placed in hypertonic, and hypotonic solutions, the hypertonic solution causes the cell to shrink, and the hypotonic solution causes the cell to increase.

Evidence: Potato cores were measured, put into various solutions, and let to sit for 24 hours. After this experiment, it was observed that the initial mass of the potatoes that were placed into the distilled water was 5.09 grams but after 24 hours, the potato core's mass increased to 6.41 grams. Also, it was observed that the potato cores placed into the 0.6 M solution had an initial mass of 5.39 grams, but after 24 hours, its mass decreased to 4.39 grams.

Reasoning: This supports the concept of osmosis. The potatoes placed into the distilled water increased in mass, which showed that the distilled water was hypotonic. On the other hand, the potatoes that were placed into the 0.6 M solution, had decreased in mass after the 24 hours which showed that the solution was hypertonic. In Osmosis, hypotonic solutions have a high concentration of water and a low concentration of solute which the distilled water contains so when the potato cores were placed into the water for a 24-hour period, the core absorbed the water while in hypertonic solutions, they contain a higher concentration of solute than water, and when the potato core was placed into the 0.6 M solution, the solute sucked the water out of it. In conclusion, this lab demonstrated that the potatoes placed into the distilled water increased in mass because the solution was hypotonic while the potatoes placed into the 0.6 M solution decreased in mass because the solution was hypertonic.