Kathryn Ancarrow
Farr AP Biology
7.03 Lab Report
3/30/17
Title: Diffusion and Osmosis: Observing Osmosis in Living Cells.
Abstract: The purpose of this lab was to observe diffusion across a cellular membrane and exactly how materials move and diffuse in concentration. Both diffusion and osmosis are forms of movement that are part of passive transport dealing with cell membranes. Potatoes were placed in 6 different sucrose solutions to determine the concertation for an allotted amount of time.
Introduction: Diffusion is where the solutes move from an area of high concentration to a low concentration; this is how water flows through cell membranes. Osmosis is specifically the movement of water through membranes. Neither osmosis or diffusion require energy or pumps to work. The process of diffusion also creates different environmental conditions; hypotonic, hypertonic, isotonic. Hypotonic environments occur when the solution has a lower solute concentration compared to the water potential. The hypertonic has a higher solute concentration and lower water potential. Finally, in an isotonic solution, there is no net movement and there is an equal concentration of solutes and water. The potato cores do not shrink because it has a cell wall which supports and maintains a plant cell structure.
Methods: After dicing the potatoes and weighing them they were placed in color-coded sucrose solutions (Red, orange, yellow, green, blue, purple). They remained in the solutions or 30 minutes, were extracted and then weighed again. This measured the rate of osmosis in the plant pieces. Other factors that could change the results would be the moisture in the potato. If the potato was placed in a dry area for several days, it may soak up more water. The materials used for this experiment included potatoes, knife it dice them, balance, ruler, cups, colored- coded solutions.
Results:
Solution Color | Initial Weight (g) | Final Weight (g) | Percent Change |
Red | 0.7 g | 0.9 g | 28.57% |
Orange | 0.7g | 0.6g | -14.28% |
Green | 0.7g | 0.6g | -14.28% |
Yellow | 0.7g | 0.6g | 14.28% |
Blue | 0.7g | 0.8g | 14.28% |
Purple | 0.7g | 0.7g | 0% |
In this experiment, the solutions in a hypotonic environment were red, yellow and blue. Those solutions al had final weights that were greater than initial weights. The orange and green colors both had final weights that were smaller than their initial weights, which means they were in a hypertonic environment. The purple color was an isotonic environment because the initial and final weights are the same.