The cell membrane is a fluid structure that is made up of phospholipids and proteins. Its main function is to allow osmosis and diffusion to occur in a cell. It protects a cell from taking in molecules that are too large and other chemicals that are not permeable without energy being used. The cell membrane is considered to be selectively permeable because it does not allow the non-fat soluble chemicals and the larger molecules in, but it does allow fat soluble chemicals and small molecules to pass into the cell.In order for the larger molecules and non-fat chemicals to enter the cell protein channels and energy are needed. In this lab you will see the cell membrane working. The experiment will show the Osmosis of water and a sucrose solution. Osmosis is net movement of water molecules from a high to low concentration until equilibrium is reached. In other words, Osmosis is the diffusion of water. Through the diffusion of water Isotonic solutions may occur. This is where both sides of the membrane have an equal amount of water. There may also be a Hypertonic solution. That is where the membrane has more water and the concentration will move down a gradient causing the membrane to shrink. Another solution that may occur is a Hypotonic solution. This type of solution allows the water molecules to pass through the cell membrane into the solution causing the cell to increase in size. Diffusion of dye in agar and water will be studied in this lab. Diffusion is the movement of a concentration from a high gradient to a lower gradient until area is at same level. We will also study the permeability of the cell membrane when different solutions are used inside and outside of the cell. In this lab, we will observe the changes taking place during the diffusion of dye through agar gel and through water. We will determine what type of solution is formed when placing the mock cell membrane in different levels of solution. We will calculate the rate at which the dye diffused and plot the findings in a chart to show the different rates each cell changed.
In Part A of the lab the cell membrane of bags 2 through 4 will gain mass because of the use of sucrose solution in the cell. The water will move through the dialysis tubing to form equilibrium between the membrane and outer concentration. Bag 5 will be a Hypertonic solution, the water is at a high gradient and the solution surrounding the cell is at a low concentration gradient, causing the bag to shrink. Bag 1 will have an Isotonic solution. In Part B of the lab, the potassium permanganate will diffuse faster in water then in the agar gel.In Part C of the lab, the solutions in the bag and the solutions around the bag will be the same after the testing is done. Starch, chloride, protein, and sulfate ions will be found in both areas tested.
Materials and Methods
See the attached sheets for materials and methods used.
Part A: In bag 1 the mass changed 1/10 of a gram. In bag 2 the mass changed 4.4 grams. In bag 3 the mass changed 6.3 grams. In bag 4 the mass changed 8.3 grams, and in bag 5 the mass changed to a negative 6.0 grams.
Part B: The methylene blue diffused through the agar gel a total of 4.5 mm and the potassium permanganate diffused 10.5 mm. The potassium permanganate diffused through the water a total of 15 mm.
Part C: The solutions in the bag contained starch, which caused the solution to turn black. Sulfate ions and proteins were not found. Chloride ions were found in the solution, the solution turned into an orange-milky color. The solutions in the beaker contained no starch. There were sulfate ions found, which caused the solution to have white particles floating in it. Chloride was found in the solution, the solution turned into a yellow color. The beaker also contained proteins, the color of the solution turned to a violet color.
Discussion and Conclusion
The findings for Part A backed up my hypothesis. Bags 2 through 4 did have a Hypotonic solution. The 5th