AP Biology Lab 1: diffusion and Osmosis

Essay by cutediva126High School, 10th grade February 2009

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Lab 1: Diffusion and OsmosisPurpose:The purpose of this lab was to understand the mechanisms of diffusion and osmosis as well as there importance to cells by using a model membrane system. Another purpose of this lab is to help describe the effects of water gain and lose in different cells, specifically animal and plant cells. Also in this lab we will learn the concept of water potential, molarity and its relationship to osmotic concentration.

Hypothesis:I believe that some molecules, like starch, will not diffuse through a membrane if they are large while small molecules such as glucose will pass through the membrane easily. Also I hypothesize that if the sucrose concentration is changed, then mass will also change. I believe this because the molarity of sucrose determines the amount of water that moves in to or out of the bag.

Materials:See attachedProcedure:See attachedData:See attachedAnalysis/Conclusion:My hypothesis proved to be correct but while doing this lab some errors were made.

These errors in our data were a result of the lack of time for our bags to stay in the solution. However, we were still able to complete the objectives of the lab and confirm our hypothesis. The molarity of the sucrose in the bag determined the amount of water that either moved into or out of the bag, which changed the mass. In the experiment, when the bag contained a 0.2M solution, water entered the bag to make the concentrations inside and outside of the bag more equal. As this occurred, the mass rose by 1.1g which can be seen on table 1.2 on page 5 of the lab. The fact that glucose which is a small molecule was able to pass through the membrane and starch a large molecule could not was indicated by the color change of the...