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Lab 3: Properties of Biological Membranes BIOL-111L Tuesday 2-5pm Professor Backil Sung Isabella Contreras Elijah Esquivel 13 March, 2019 1
Abstract Diffusion has always been important as one of the many basic elements in cell membranes. In this lab we were able to observe diffusion and osmosis through different concentrated solutions. In the first exercise we observed solutions in pre-punched holes on agar plates to determine the diameter of each spot. The bigger the weight the slower the rate of diffusion and in constant rate there is equilibrium. In exercise two dialysis tubing was used to differentiate smaller molecules from larger molecules. The indicators used were phenolphthalein for ph and iodine for starch. We obtained 2 dialysis tubing and tied both ends once both were filled with distilled water and the indicator, making sure to not have any air inside. Once this is done we observed the bags in different beakers, one with 1M NaOH and the other with 30 drops of iodine to see their color changes and movement. Bags A and B had “movement out” and bags C and D had “movement in.” In exercise three we observed osmosis with four new tubes and solutions identifying hypertonic, hypotonic, or isotonic. The contents used were 3mL of 1% sucrose, 0.9% NaCl, 10% sucrose, and 25% sucrose. Once weighed the bags were put into a 600 mL beakers filled halfway with 1% sucrose, and a 250 mL beaker filled halfway with 25% sucrose. Once put in beakers record weights of the bags at 15 minute intervals four times. Exercises four, five required fov’s, already provided, of osmosis in erythrocytes in hypertonic, hypotonic, and isotonic environments. The difference in exercise five is involvement of plasmolysis. Exercise six tested for solvent stress in membranes in the depiction of absorbances: 25% acetone was 0.321, 50% acetone was 0.527, 35% ethanol was 0.455, 70% ethanol was 0.665, and 0.9% NaCl was 0.214. The higher the percentage the more absorbance was recorded. Using a spectrophotometer can help determine the amount of pigment that is absorbed in a solution. This can help in distinguishing blood samples and the factors in them. Word Count: 300 2
Introduction: Dialysis tubing, also known as Visking tubing, was brought into the world around the late 1800s to early 1900s with the help of Thomas Graham. By the 1940s the first tube was officially produced and approved for the use of a patient. With the use of dialysis tubing we are able to we are able to find osmotic pressure, temperature, size of molecules, and molecular weight. In dialysis tubing one is able to mimic the idea of the process of kidneys. According to “Journal of Kidney,” in having lost kidney function, one is able to use dialysis tubing to remove toxins from a patient’s bloodstream. It is used as a filter to let specific particles pass or block ones that shouldn’t be allowed in the bodily function.