Ap Bio Lab One: Osmosis and Diffusion

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Meghann Kiphart
AP Biology
Lab Report Number One
Mrs. Irvine

Introduction:
Because all molecules have kinetic energy and are constantly in motion cells go through a process called diffusion. Diffusion is the movement if molecules from an area of higher concentration to and area of lower concentration. This process with continue to occur until an equilibrium is reached. Osmosis is a different and unique kind of diffusion. Osmosis is the diffusion of water through a permeable membrane. The phrase “permeable membrane” means that the membrane will only allow specific molecules through such a water or oxygen. In Osmosis water will travel from an area of higher water potential or an area of lower water potential. Hypothesis:

I think that in this lab, osmosis and diffusion will occur between the solutions of different concentrations until a equilibrium is reached and there is no movement of water. Materials:
EXERCISE 1A: Diffusion
The materials include a 30-cm piece of 2.5-cm dialysis tubing, 15-mL of the 15% glucose/1% starch solution, 250-mL beaker, distilled water, 4-mL Lugol’s solution, and string.
EXERCISE 1B: Osmosis
The materials used include 25-mL of these solutions: distilled water, 0.2M sucrose, 0.4M sucrose, 0.6M sucrose, 0.8M sucrose, and 1.0M sucrose, scissors, string, a balance, six 250-mL cups, and six 30cm strips of dialysis tubing. EXERCISE 1C: Water Potential

The materials that were used included 50mL of distilled water, 0.2M sucrose, 0.4M sucrose, 0.6M sucrose, 0.8M sucrose, and 1.0M sucrose, six 250mL cups with lids, 4 potato cores for each cup, a balance, and paper towel.

EXERCISE 1D: Calculation of Water Potential from Experimental Data This exercise required a calculator and a pencil.
Procedure:
EXERCISE 1A:
Soak the dialysis tubing in water before you start the experiment. Tie off one end of the tubing to form a bag like structure. Through the open end of the bad, place the starch solution in to the bag. Tie off the other end of the bag to secure the substance inside. Make sure to record the color of the solution in Table 1.1. Next you’re going to text the starch solution for the presence of glucose. Record the results in Table 1.1. Fill a 250ml cup about 2/3 of the way full with distilled water. Add 4ml of Lugol’s solution into the distilled water. Record the color of the solution in the Table 1.1. Put the bag in the cup full of the solution. Allow the bag and cup to stand over night. The next day record the final color of the solution in Table 1.1. Finally test the liquid in the cup and in the bag for the presence of glucose. Record the final results in Table 1.1. EXERCISE 1B:

Get six strips of presoaked dialysis tubing and create a bag like was shown in exercise 1A. Pour 25mL of the six solutions into each of the six bags. Tie off the other end of the bags. Rinse each bag gently with distilled water and dry the outside of the bag with a paper towel. Weigh each bag and record the results in Table 1.2. Put each of the six bags into the cups with the six different solutions. Let stand over night. The next day remove the bags from the water and carefully dry the bags with paper towel. Weigh each bag and record them in Table 1.2. Gather the other lab group’s data to be able to complete Table 1.3. EXERCISE 1C:

Pour 50mL of the solutions into a labeled 250mL cups. Using a cork borer, cut the potato into 24 cylinders. (4 potato cores x 6 cups = 24 potato cores altogether) weigh the mass of each set of 4 potato cores. Record the data in Table 1.4. Put 4 potato cores into each solution cup. Cover the cup with a lid to prevent evaporation. Let stand overnight. Remove cores from the cup and dry them with a paper towel. Then determine there combined weigh in groups of 4 (from the same cup). Record the results in Table 1.4. Calculate the percentages changes in mass. Collect the class data and determine the class change in mass. EXPERIMENT 1D:...
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