Osmosis Jones Penetrating the Membrane Essays - Chemistry

Osmosis Jones: Penetrating the Membrane By Emma Nicholas Jeffrey O'Hara First Lab Report 40811 Tuesday, Wednesday, Thursday at 12:45pm-3:45pm July 17, 2013 Theresa Gburek Abstract: The objectives in the osmosis lab include the following; how concentration gradients influence the direction of net water flow during osmosis. Also, how a selectively permeable membrane allows selective diffusion of various substances. In addition, how to create serial dilutions for use in laboratory experiments. Lastly, how to generate hypotheses and test them experimentally. The methods used in this lab include the creation of dilutions and the preparation of dialysis tubing. An important part of this experiment is the use of solutions with known concentrations of solute. Dialysis tubing is a kind of membrane that allows water to pass through it, which lets us observe osmosis in action. The results are presented in a graph displaying the gradual increase of weight throughout the osmosis experiment with the exception of a malfunctioned dialysis tubing in which case a portion of the experiment was disrupted. Concluding that throughout osmosis the weight of the bag increases becaus e of the exchange of molecules between the membrane and surrounding water. Introduction: Living organisms are made up predominantly of water. Proteins, sugars and many other biologically important molecular are dissolved in this solvent. Plasma membranes, however, are made up of lipids, which are hydrophobic. Thus, the plasma membrane is able to compartmentalize cells and organelles in an aqueous environment. It is, however, selectively permeable: some substances can flow freely across the membrane, some require assistance, and some cannot cross it at all. Transport proteins help move some molecules through membranes. Diffusion is the simplest form of flow across membranes. Osmosis is the form of diffusion in which water, not the solutes dissolved in it, flow across the membrane. During the time lapse of this experiment, questions and hypotheses were either asked and or addressed. (E.g.) Temperature, viscosity and concentration gradients will affect the rate at which molecules move across a membrane. However, what happens when the solutes reach equilibrium? What are the differences between hyper- and hypotonic solutions? What happens when two solutions have the same concentration? Our hypothesis on osmosis is as follows; increased concentration gradient will change water flow due to osmosis. "Many desalination plants around the world rely on reverse osmosis membranes, which enable water molecules to separate from brine with the application of power" (Winters, 2010). "RO [reverse osmosis] can treat for a wide variety of health and aesthetic contaminantsRO [reverse osmosis] also can be effective for treating health contaminants such as arsenic, asbestos, atrazine (herbicides/pesticides), fluoride, lead, mercury, nitrate and radium" (Harrison, 2006). Materials and Methods: For this experiment, the following materials are required, sucrose, 4 15cm lengths of dialysis tubing, 8 10cm pieces of waxed dental floss, 4 400mL beakers, 25mL graduated cylinder, tags, ring stand, wax pencil, balance, distilled water, scissors and compound microscope. The procedure for this experiment begins with obtaining the required materials (which are listed above). First step is to tie one end of the dialysis tubing with the waxed dental floss. Then prepare the sucrose solution that will fill the dialysis tubing. Measure out the amount of sugar using a balanced scale, adding the appropriate amount of sugar in the solution to obtain the desired sucrose content. Before beginning the test, mix up a 0% solution, 15% sucrose solution, 30% sucrose solution and a 90% sucrose solution. Then fill four different dialysis tubing with the prepared sucrose solutions, and then tie off the top. Weigh each tube before the experiment. Place each of the filled tubing into the corresponding labeled beaker. After the passing of 5 minutes, remove each bag from its beaker, then weigh and record the weight changes. Repeat this step for the next 30min. In this experiment the independent variable is the percentage of sucrose solution. Decreasing and increasing the percentage of sucrose altered this variable. The dependent variable is the weight of the tubing contents. During our osmosis lab, there was no positive control. However, our negative control was the dialysis tubing filled with only water (i.e.) 0% sucrose solution. Results: The Y-axis represents the amount of grams each tube weighed. The X-axis represents the time at which the bags were weighed. This represents the recorded quantitative