Cells have kinetic energy. This causes the molecules of the cell to move around and bump into each other. Diffusion is one result of this molecular movement. Diffusion is the random movement of molecules from an area of higher concentration to areas of lower concentration. Osmosis is a special kind of diffusion where water moves through a selectively permeable membrane (a membrane that only allows certain molecules to diffuse though). Diffusion or osmosis occurs until dynamic equilibrium has been reached. This is the point where the concentrations in both areas are equal and no net movement will occur from one area to another. If two solutions have the same solute concentration, the solutions are said to be isotonic. If the solutions differ in concentration, the area with the higher solute concentration is hypertonic and the area with the lower solute concentration is hypotonic. Since a hypotonic solution contains a higher level of solute, it has a high solute potential and low water potential. This is because water potential and solute potential are inversely proportional. A hypotonic solution would have a high water potential and a low solute potential. An isotonic solution would have equal solute and water potentials. Water potential (y) is composed of two main things, a physical pressure component, pressure potential (yp), and the effects of solutes, solute potential (ys). A formula to show this relationship is y = yp + ys. Water will always move from areas of high water potential to areas of low water potential. The force of water in a cell against its plasma membrane causes the cell to have turgor pressure, which helps maintain the shape of the cell. When water moves out of a cell, the cell will loose turgor pressure along with water potential. Turgor pressure of a plant cell is usually attained while in a hypotonic solution. The loss of water and turgor pressure while a cell is in a hypertonic solution is called plasmolysis. Hypothesis:
During these experiments, it will be proven that diffusion and osmosis occur between solutions of different concentrations until dynamic equilibrium is reached, affecting the cell by causing plasmolysis or increased turgor pressure during the process. Materials:
Lab 1A - To begin Lab 1A, first collect the desired equipment. The materials needed are dialysis tubing, Iodine Potassium Iodide (IKI) solution, 15% glucose/ 1% starch solution, glucose Testape or Lugol’s solution, distilled water, and a 250-mL beaker. Lab 1B - For Lab 1B you will need to collect six presoaked dialysis tubing strips, distilled water; 0.2M, 0.4M, 0.6M, 0.8M, and a 1.0M sucrose solution; six 250-mL beakers or cups, and a scale. Lab 1C - Lab 1C these items are needed: a potato, knife, potato core borers, six different solutions, and a scale. Lab 1D - During Lab 1D, only paper, pencil, and a calculator will be needed to make the calculations. Lab 1E - n Lab 1E these items are needed: a microscope slide, cover slip, onion cells, light microscope, and a 15% NaCl solution. Procedures:
Lab 1A - After gathering the materials, pour glucose/starch solution into dialysis tubing and close the bag. Test the solution for presence of glucose. Test the beaker of distilled water and IKI for presence of glucose. Put the dialysis bag into the beaker and let stand for 30 minutes. When time is up test both the bag and the beaker for presence of glucose. Record all data in table. Lab 1B - Obtain the six strips of dialysis tubing and fill each with a solution of a different molarity. Mass each bag. Put each bag into a beaker of distilled water and let stand for half and hour. After 30 minutes is up, remove each bag and determine its mass. Record all data in its appropriate table. Lab 1C - using the potato core borer, obtain 24 cylindrical slices of potato, four for each cup. Determine the mass of the four cylinders. Immerse four cylinders into each of the six beakers or cups. Let...
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