Results:
Preliminary Test Results
1. What happened when you placed a drop of iodine into the starch solution?
There was a color change from yellow to purple when placed a drop of iodine into the starch solution.
2. What happened to the sugar solution and Benedict’s when heated?
The color changes from blue to orange when we heated the sugar solution and Benedict’s.
3. What happened during the experiment while the dialysis tubing was placed in water?
While the dialysis tubing was placed in water, glucose diffused out of the dialysis tubing and water went in by osmosis.
4. What happened to the fluid in the beaker that contained the dialysis tubing after it was heated with the Benedict’s solution?
The fluid in the beaker that contained the dialysis tubing turned from blue to orange after it was heated with the Benedict’s solution
5. A membrane that allows some molecules to pass but not the others is called?
The membrane that allows some molecules to pass but not the others is called a semi permeable membrane.
6. Can material pass through a membrane in both directions at the same time? Support your statement.
Yes. According to our observations from this experiment, glucose was able to go through the membrane to the beaker while water goes in to the bag.
7. In what way is the dialysis membrane like the cell membrane?
Both the dialysis membrane and the cell membrane is semi permeable, it allows certain substances to enter and exit the bag/cell.
8. Indicate the direction of net flow through the membrane of each of the following substances. Support your answer by using the preliminary test results.
a) Iodine – no flow
b) Starch – no flow
c) Glucose – from high concentration to low concentration
d) Water – from high concentration to low concentration
Discussion:
1. Why do molecules diffuse?
Molecules will keep diffusing from an area of high concentration to an area of low concentration until dynamic equilibrium is met so that they are equally spread.
2. Why would molecules of a gas diffuse more rapidly than those of a liquid?
Liquid molecules have a stronger bond than the molecules of gas, that’s why gas molecules move more quickly than liquid molecules.
3. The shrinking of cytoplasm within cell from diffusion is known as?
Plasmolysis is the shrinking of cytoplasm within cell from diffusion. Plasmolysis occurs when the cell is in a hypertonic environment causing the cell to loose water and shrivel.
4. How can this shrinking be a disadvantage to a cell?
As the cell loses water, the concentration of solvents will be too high which could cause death.
5. A cell contains 3% of salt and 97% water. How would this cell respond if placed in a beaker of distilled water?
The distilled water will go into the cell until the solute concentrations are equal. As the cell gains too much water, it would burst and die. (animal cell would die but not plant)
6. For the most part, plants, and animals live in either a salt water environment or a fresh water environment, not both. Explain the reason for this using the principles of diffusion.
Most plants and animals can’t live in both salt water environment and fresh water environment because animals or plants that live in salt water is used to the environment that has more salt and less water. When they are placed in fresh water, its environment become hypotonic to the cell. This would result in water entering the cell causing it to lyse. As for animals or plants that live in freshwater, they are used to an environment with more water and less salt. When they are placed in salt water, its environment become hypertonic to the cell resulting water leaving the cell. Once the water leaves the cell, it becomes plasmolyzed.
