Lab Report 1

Lab Report 1 - Diffusion across semi-permeable membranes...

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Diffusion across semi-permeable membranes Elliot Mitchell Bio 101, Lab section 7 October 3, 2007 Abstract: In this lab we performed five experiments in order to determine which solutes move across a semi-permeable membrane. This lab lets us visually see which substances were able to diffuse across the membrane, such as iodine and starch. Introduction: In experiment one we measured the rate of diffusion of solutes. We were testing to see whether solutes placed into a gelatin like mixture would diffuse faster or slower according to temperature. My guess is that the solute will diffuse slower in the colder gelatin due to the reduced speed of the molecules. In experiment two we placed varies solutions into small baggies to test the baggies semi-permeability in accordance to the solution in the bag and the solution in the beaker. We estimate that the bags with a greater concentration of sucrose will gain more water while the water on water dialysis will keep a constant weight. In the third experiment we placed a sucrose and water solution in a bag and placed it in a water and iodine solution to wait about ten minutes then to record the results. Then we tested for starches. We decided that the sucrose will not leave the bag because the starch molecules are to large. In experiment four we tested plasmolysis of a plant cells. We did this in order to determine what would happen if a plant cell was place in a hypertonic or hypotonic solution solution. We think that in a hypertonic solution the plant cell will shrivel, in a hypotonic the cells will increase in size. In experiment five we tested the osmotic changes in red blood cells. In short we tested what a blood cell will do in a hypotonic, hypertonic, or isotonic solution. We are sure in a hypotonic solution the cells will burst, in a hypertonic they will get smaller, and in an isotonic solution everything will stay the same. Method and Materials: 7.1 rate of diffusion, we were provided pictures of before and after shots of the hot and cold test tubes. Two sets of three screw cap test tubes were used, three marked room temp and three marked 5 degrees Celsius. Each test tube was filled half way with
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Lab Report 1 - Diffusion across semi-permeable membranes...

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