Unformatted text preview: Diffusion Shana Fowler Kristin Robb Andrea Sciulli Plasma Membranes Plasma membranes consist of a phospholipid bilayer, with a hydrophobic interior and a hydrophilic exterior. Diffusion Diffusion is the tendency of molecules or particles of a particular substance to move from areas of high concentration to areas of low concentration of that substance. Diffusion is the consequence of random thermal motion which will make the concentrations more equal. Concentration Gradient Difference in concentration from one space to another is called a concentration gradient. Eventually an equilibrium will be reached in which the particles uniformly fill the available volume. The steeper the concentration gradient, the higher the rate of diffusion. Purpose To determine which molecules are able to diffuse through a semipermeable membrane by using a dialysis tube, which will represent the membrane. Hypothesis The permeable molecules will be uncharged and small enough to be able to pass through the bag and change its weight. Null Hypothesis The molecules that are uncharged and small will not able to pass through the membrane, meaning there will be no change in the weight of the bag. Predictions/Rationales 1) When Silver Nitrate is added to the solution, it will change from clear to a cloudy white, indicating the presence of NaCl. Rationale: NaCl is a neutral compound with no charge, so it should be able to pass through the membrane easily. Predictions/Rationales 2) When Benedict's Test is used to test for glucose, the color will turn from turquoise blue to green, because only a small amount of glucose will be able to pass through. Rationale: Glucose passes through membranes very slowly because it is a large molecule . The water will diffuse into the bag because of the high concentration of glucose. Predictions/Rationales 3) When Iodine is added to test for the presence of starch, the solution will remain yellow because no starch should be able to pass through. Rationale: Starch will not be able to pass through the semipermeable membrane because it is extremely large and made of many glucose molecules. Predictions/Rationales 4) When an Albustix reagent strip is used to test for the presence of proteins, the strip should change colors because proteins are able to easily pass through the membrane. Rationale: Proteins are able to diffuse easily because they are hydrophobic. ...
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- Fall '06
- Osmosis, Molecular diffusion, Kristin Robb Andrea Sciulli