Madelyn N. Laird



Osmosis Through Simulated Cells Lab Report Maddie LairdHonors Biology 10, Period 4Cardinal Wuerl North Catholic High SchoolApril 30, 2018Introduction: Passive transport is a type of cell transport that occurs whenever particles/molecules move from a high concentration to a low concentration across a cell membrane. Passive transport does not require any extra energy from the cell (ATP or any other energy storing molecules). Passive transport also happens naturally and moves with the concentration gradient (high concentration to low concentration) (Cooper, 1970). Passive transport is evident in both part 1 and part 2 of this lab. Passive transport can happen within a cell membrane when it is selectively permeable. When a cell membrane is selectively permeable, this means that it allows certain substances (inside or outside the cell) to pass through it. A living cell membrane is selectively permeable and can change its permeability as needed. That being said, living cell membranes allow certain molecules of substances, such as water and carbon dioxide, to pass through it at certain times (Biggs, 2017). In this lab, students represent simulated cells with dialysis tubing. The purpose of this material is to imitate the semi-permeable cell membrane. Because of this tubing, diffusion of smaller substances can to pass through while some larger molecules cannot. One example of simple diffusion that is able to be transported through a selective-permeable membrane is osmosis. Osmosis is the movement of water across a cell membrane from high concentration to low concentration. In order for osmosis to occur, it needs to pass through channel proteins called aquaporins, which are always open (Cooper, 1970). In order for osmosis to happen, there needs to be osmotic solutions, which are solutions or environments that cells are placed into to prompt osmosis. There are 3 types of osmotic solutions: a hypotonic environment, an isotonic environment, and a hypertonic environment (Biggs, 2017). In a hypotonic environment, there is a higher concentration of pure water outside of the cell compared to inside the cell. As a result, water moves into the cell which can cause it to burst (cytolysis). In an isotonic environment, equilibrium is reached because the concentration of a substance inside the cell is the same as the concentration outside of the cell. Therefore, an isotonic environment is the ideal environment for cells. In a hypertonic environment, there is a low concentration of pure water outside the cell compared to the inside of the cell. Because of this, water wants to move out of the cell, which causes the cell to shrivel (Biggs, 2017). These osmotic environments can be applied in many realistic scenarios. For example, drinking too much water in a relatively short period of time can place red blood cells into a hypotonic environment. Because of this, the red blood cells can explode and lead to death. Additionally, fresh produce is often sprayed with water in order to increase turgor pressure. Turgor pressure occurs in a hypotonic environment and whenever the force of water is pushing against the cell wall. This can cause the enlargement of certain foods, particularly in plants. This is especially evident when soaking rice, nuts, or beans in water (Deziel, 2018). Other examples of osmotic solutions in real-world include IVs, pruning, and parameciums. Even though there are many realistic ways to observe the different types of osmotic solutions in everyday life, it is also important to observe this through a scientific lens, such as a lab. This lab consists of 6 beakers that represent the osmotic solutions and 6 dialysis tubes that represent 6 simulated cells. In part 1, there are 6 beakers and 6 simulated cells used. Beaker 1 (water) represents a simulated cell in an isotonic environment. Beakers 2, 3, and 4 (water) represents simulated cells in a hypotonic environment. Beaker 6 also represents a simulated cell in a hypotonic environment even though the beaker is full of 60% glucose solution as opposed to 100% of pure water. Lastly, beaker 5 (60% glucose solution) represents a simulated cell in a hypertonic environment. For part 1 of this lab, the purposes are to show how different concentration gradients affect the rate of osmosis, to help students understand how the semi-permeability of certain materials affect osmosis, to observe the effects of osmosis within a hypotonic, isotonic, or a hypertonic cell environment, and to see how time (the closer you get to equilibrium) affects the rate of osmosis. The dependent variable for part 1 is the mass for the simulated cell while the independent variable is the amount of glucose in the solution. Basically, the independent variable is measuring in what type of environment the cell is placed. Additionally, for part 1, the constants include: the amount (5 mL) of whatever solution (glucose) in the simulated cell, the amount (200mL) of water or solution, how the simulated cell is tied, how the simulated cell is filled, how it is submerged in the water, how it is dried, weighed, and timed. The control group is the simulated cell that contains pure water and is placed into a beaker with pure water. Lastly, for part 1, the experimental group is the other 5 beakers that contain different amounts of glucose solution. For part 2 of this lab, the purpose is to see what other substances can permeate the simulated cell. The dependent variable for part 2 is the color changes in both the simulated cell and the beaker while the independent variable is the placement of the starch. Additionally, the constants for part 2 are the amount of iodine (20 drops) placed into the beaker, the ? spoonful of starch into the simulated cell, and the washing off of the simulated cell before placing it into the beaker. The control group for part 2 is the original setup, whenever the starch solution is clear inside the simulated cell. Lastly, the experimental group is the setup, whenever there is dark blue (violet) inside the simulated cell. Because there are 6 simulated cells used in part 1 of this lab and just 1 in part 2, there will be 7 hypotheses in total:If the simulated cell containing 5mL of pure water is placed into a beaker with 200mL of water, then the mass change will fluctuate slightly because the simulated cell is paced in an isotonic environment. If the simulated cell containing 5mL of 20% glucose solution is placed into a beaker with 200mL of water, then the mass change will increase because the simulated cell is placed in a hypotonic environment. If the simulated cell containing 5mL of 40% glucose solution is placed into a beaker with 200mL of water, then the mass change will increase because the simulated cell is placed in a hypotonic environment. If the simulated cell containing 5mL of 60% glucose solution is paced into a beaker with 200mL of water, then the mass change will increase because the simulated cell is placed in a hypotonic environment. If the simulated cell containing 5mL of pure water is placed into a beaker with 60% glucose solution, then the mass change will decrease because the simulated cell is placed in a hypertonic environment. If the simulated cell containing 5mL of 80% of glucose solution is placed into a beaker with 200mL and 60% glucose solution, then the mass change will increase because the simulated cell is placed in a hypotonic environment. If the simulated cell containing ? spoonful of starch into a half-filled beaker with water and approximately 20 drops of iodine, then after 24 hours, the simulated cell will change color.Materials: 6 Beakers20% of glucose solution40% of glucose solution60% of glucose solution80% of glucose solutionPure Water SolutionSimulated Cells (Dialysis tubing)Corn starchScaleStringPaper towelsTimerPipettesIodineGraduated cylinderProcedure:Part 1: Gather 5 beakers and fill 4 of the beakers with 200mL of pure water. For the 5th beaker, fill it with 200mL of 60% glucose solution. Prepare the 6 simulated cells, which were previously submerged in water, by filling each simulated cell with their designated amounts of substances (5mL of water and ___% of glucose solution) with a pipette. Fold down the open end of the bag by 1 inch from the top, folding that same fold across, and then folding that fold down again. Then, tie a very tight knot with string in the middle of that fold. Weigh each simulated cell on a scale separately to find the original masses. Record each original mass on data sheet.Place the simulated cells containing 5mL of pure water, 5mL of 20% of glucose solution, 5mL of 40% of glucose solution, and 5mL of 60% of glucose solution into the first 4 beakers containing 200mL of pure water. Then, place the remaining simulated cells containing 5mL of pure water and 5mL of 80% of glucose solution into the 5th beaker filled with 200mL of 60% glucose solution. Make sure that all simulated cells are placed into the specific beaker at the exact same time. Start timer to designate 3 minutes. When 3 minutes has elapsed, take out each simulated cell at the exact same time. Dry each simulated cell off with a paper towel to eliminate any excess water. Weigh each simulated cell on the scale separately to find the first mass change. Record mass change on data sheet. Repeat the same steps (7-9) 2 more times, each at 3 minute intervals. Be sure not to confuse the simulated cells and to record each mass change on data sheet. Part 2:Prepare 1 simulated cell by filling it with a ? spoonful of starch solution. Fold the simulated cell the same way in part 1 above. Rinse the simulated cell off with water to eliminate any excess starch on the outside of the simulated cell. Then, dry off the simulated cell with a paper towel. Fill 1 beaker approximately half way with pure water.Add approximately 20 drops of iodine to the beaker.Place simulated cell into the beaker and let sit for approximately 3 days. Remove the simulated cell from the beaker and record the color change inside the simulated cell and in the beaker on data sheet. Results: Table 1: Mass Changes of Simulated Cells Over TimeTime Water in Water20% in Water 40% in Water 60% in WaterWater in 60%80% in 60%00000003208317408567-15024162915348001009-533316924970111081409-783399-256540331152500Description: All simulated cells’ masses in the table above start at 0 mg. In order to show the mass change over a period of time on a graph, masses are needed for 0, 3, 6, and 9 minutes. Mass changes from 0-3, 3-6, and 6-9 minutes were averaged from multiple groups, since all groups did not have the same initial masses. These averages of mass change were then used to determine the masses at 3, 6, and 9 minutes in the table above. All of the masses at 3 minutes are the average mass changes from 0-3 minutes. All of the masses at 6 minutes are the average mass changes from 3-6 minutes added to the mass at 3 minutes. All of the masses at 9 minutes are the average mass changes from 6-9 minutes added to the mass at 6 minutes. Figure 1: Mass verses Time of Simulated Cells Description: The graph above demonstrates all the mass changes from 0-3, 3-6, 6-9 minutes of each of the 6 simulated cells from the data table above. The dark blue line on the graph represents the mass change of the simulated cell that contained pure water and was placed into a beaker with pure water also. The orange line on the graph represents the mass change for the simulated cell that contained 20% of glucose solution and was placed into a beaker with pure water. The gray line on the graph represents the mass change for the simulated cell that contained 40% of glucose solution and was placed into a beaker with pure water. The yellow line on the graph represents the mass change of the simulated cell that contained 60% of glucose solution and was placed into a beaker with pure water. The light blue line on the graph represents the mass change of the simulated cell that contained pure water and was placed into a beaker with 60% of glucose solution. Lastly, the green line on the graph represents the mass change of the simulated cell that contained 80% of glucose solution and was placed into a beaker with 60% of glucose solution. For part 2, there was a very apparent color change both within the beaker and the simulated cell. At first, the water within the beaker was yellow because of the 20 drops of iodine added and the starch solution inside the simulated cell was white. Once the simulated cell was placed into the beaker and remained there for approximately 24 hours, the water within the beaker was somewhat clear and the solution in the simulated cell was dark blue/violet. Discussion: During part 1 of this lab, it was apparent that certain simulated cells either gained weight or lost weight according to the data. The data showed the average mass changes of all the simulated cells from 0-3, 3-6, and 6-9 minutes. There were certain mass changes because each simulated cell was placed into a certain osmotic environment. For example, the first simulated cell that contains 5mL of pure water was placed into a beaker with 200mL of pure water. The mass change, represented in the data table and on the graph, represents a slight fluctuation because it is placed in an isotonic environment. Because this simulated cell is paced in an isotonic environment, both the simulated cell and the beaker have the same, pure concentration gradient with no solutes. Not to mention, this simulated cell represents the achievement of reaching equilibrium. As the simulated cell becomes closer to equilibrium, then the rate of osmosis decreases. When there is a greater concentration gradient, the rate of osmosis will be fast because it wants to reach equilibrium. The second simulated cell that contains 5mL of 20% glucose solution and is placed in 200mL of pure water is placed in a hypotonic environment because there is a greater concentration of water outside of the cell. Because of this and the fact that osmosis transfers water from a high to low concentration, water will be moving inside of the simulated cell, causing an increase in mass. This same information applies to the simulated cells that contained 5mL of 40% glucose solution placed in 200mL of pure water, 5mL of 60% glucose solution placed in 200mL of pure water, and 5mL of 80% glucose solution in a beaker with 60% glucose solution. The simulated cell that contained 80% of glucose solution and was placed in a beaker with 60% glucose solution did not gain as much weight from 0-3 minutes as the simulated cell that contained 5mL of and was placed in a beaker with water because the 80/60 simulated cell was placed in a hypotonic environment compared to an isotonic environment. However, the simulated cell that contains 5mL of pure water and is placed into a beaker with 200mL and 60% glucose solution is placed in a hypertonic environment. This is because there is a higher concentration of water inside the cell and a lower concentration of water outside the cell. Because of this, water will be moving outside of the simulated cell, causing a decrease in mass. In part 2 of the lab, the inside of the simulated cell turned from white to a dark blue/violent because the simulated cell is permeable to both iodine and water but not to starch. Conclusion:In conclusion, this lab showed us first-hand the process of osmosis by experimenting with the 3 different osmotic environments and the permeability of simulated cells. This lab truly helped me understand how osmosis works within different substances, the informational reasoning behind the different osmotic solutions, the permeability of simulated cells, and how to interpret data. It was also very interesting to learn that all my hypotheses were supported because I used trustworthy resources and previously learned information to make the lab predictions. However, I did notice some sources of error that I would be sure to improve upon when conducting this lab again. A very large source of error was the fact that this lab was completed in a very short time period, which increased rushing and mistakes. I think it would have been better if the lab was spaced out a little bit more so my group and I could see our simulated cell reach equilibrium. Additionally, I would have made sure to write my data more clearly to eliminate confusion or misconception along with noting certain important aspects of the lab as I went along. For example, when completing the lab, it would have been nice to discuss with my group what the dependent and independent variables were, the constants, the experimental group, etc. Lastly, I think it would have been very beneficial to record the process of the simulated cell in part 2 changing colors (from white to dark blue) in a time-lapse. That way, I could witness first-hand a simulated call being selectively permeable to water and iodine. References:Work Cited:Biggs, A. (2017).?Glencoe biology. Columbus, OH: McGraw-Hill Education.Cells and Diffusion. (n.d.). Retrieved from , G. M. (1970, January 01). Transport of Small Molecules. Retrieved from , C. (2018, March 13). Osmosis Facts for Kids. Retrieved from ................
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