Diffusion Across Plasma Membrane Lab Report

Diffusion Across a Plasma Membrane Lab The purpose of this lab was to learn about the permeability of plasma membranes. In this experiment, dialysis tubing was used to simulate the semipermeable plasma membrane of a caterpillar’s intestine. Cooked starch was prepared and mixed with the enzyme amylase to simulate the mixing of the caterpillar’s saliva with a starch/leaf and then placed in the dialysis tubing to simulate the beginning of the digestive process. The enzyme amylase breaks down starch into glucose and that glucose then is able to permeate the membrane of the caterpillar’s intestine. Lugol’s solution is able to detect when a starch is present and, if present, turns the solution blue/black. Lugol’s solution was placed in the surrounding …show more content…
The small beaker where the starch was held was clear at the beginning and end of this experiment and the glucose levels were normal. The amylase mixture was cloudy at the beginning and end of this experiment and the glucose was not present. In the “intestine” (dialysis tubing where the amylase and starch mixture was held), the color was cloudy at the beginning and at the end of this experiment. The glucose test read “500”. In the “cell membrane”, the color at the beginning and end of this experiment was brownish orange. The glucose test read “1000”. In the control group, the dialysis bag was clear at the beginning of the experiment and was blueish black by the end of the lab. The large beaker that contained the control group was brownish orange at the beginning and at the end of the lab. The glucose test was not applicable for the control …show more content…
To do this, red blood cells were examined in solutions of three different saline concentrations, 9% salt concentration, 1.8% salt concentration, and 0% salt concentration. A solution of 9% salt is isotonic to red blood cells. A solution of >9% salt is hypertonic to red blood cells. A solution of <9% is hypotonic to red blood cells. In tube one, the blood cells were placed in a tube with the volume of stock 300mM NaCl was 1.00 ml with no water. In tube two, the blood cells were placed in a tube with the volume of stock 300mM NaCl was .50 ml and there were 0.50 ml of water. In tube three, the blood cells were placed in a tube with no NaCl and 1.00 ml of water. After the blood cells were placed in their tubes, the blood cells were swirled and were observed after one to five minutes. I hypothesize that when the red blood cells are placed in the 9% salt concentration, the blood cells will not change since the amount of water flowing into the cell is equal to the amount of water flowing out of the cell. I also hypothesize when placed in the solution with a solution of 1.8% salt, the blood cells will shrivel up in a process called crenation. When the blood cells are placed in the solution with no salt, I hypothesize that the blood cells will explode from the influx of water entering into the cells. My null hypothesis is that the 1.8% solution will not cause