Ap Biology Diffusion And Osmosis Lab Report 5e483r

INTRODUCTION All molecules have kinetic energy and are constantly in motion1. This motion causes the molecules to bump into each other and move in different directions. The results are two ive transport movements that deal with the cell membrane: diffusion and osmosis. Diffusion is where the solutes move from an area of high concentration to a low concentration. Water also goes through the cell membrane by diffusion2. Osmosis is specifically the movement of water through membranes. Since osmosis and diffusion are both part of ive transport, this means that they do not require energy or pumps. Because of this, there are different environments created due to diffusion. They are the hypotonic, hypertonic, and isotonic environments. Hypotonic is when the solution has a lower solute concentration compared to the water potential. The hypertonic solution, however, has a higher solute concentration and lower water potential. In an isotonic solution, there is no net movement and there is an equal concentration of solutes and water. In our lab, we modeled diffusion and osmosis with an interesting scenario. It is important for a solution to have salts in it so the water and solute can be equal to create an isotonic environment. However, if there was nothing, it would either be a hypotonic causing the cell to expand and burst or it would be hypertonic causing the cell to shrink. We can create models of living cells by using dialysis tubing. The dialysis tube represents a cell membrane, which will act as being selectively permeable to water and some solutes. We will observe the solutes sodium chloride, ovalbumin, glucose, sucrose, and water in the dialysis tubing. The purpose of this experiment is to figure out the type of environment the solutes would create with the water and whether the water would diffuse in or out of the cell, or in this case the tubing. My hypothesis

1 http://chemwiki.ucdavis.edu/Physical_Chemistry/Thermodynamics/State_Functions/Kinetic_Energy 2 http://www.biologycorner.com/bio1/notes_diffusion.html

states that all of the tubes will be in a hypotonic environment after several minutes or hours because there will be a higher concentration of water outside of each tubing. The water will diffuse inside the cell; therefore the cell will gain weight. We took the initial weight of each tube with the solute inside, the final weight, and then after that, we took the percent change in weight. The control of the experiment was the beaker where there was water inside and outside of the tubing. For the second part of the experiment, we were to use potatoes to observe them in different liquid substances. The purpose was to identify concentrations of sucrose solutions that we were given. We were to find what solution was closest to being isotonic in order to identify which of them was water. There were six different solutions that we observed. Each solution was in a red, orange, yellow, green, blue, and purple color. A tubular slice of potato was to be placed in each of the solutions. My hypothesis states that the potato would remain the same size in the warm colored solutions because it would have an isotonic environment and, because it is sucrose, a sugar found in most plants, it would probably be in an equilibrium state. I also believe that if the potato was placed in a hypotonic environment, then the percent change in mass would be greater than if placed in a hypertonic environment.

RESULTS Table 1 – Data Results Got From Modeling Diffusion and Osmosis (Part 1) Solute

Initial Weight (g)

Final Weight (g)

Percent Change

NaCl

11.74 g

12.88 g

9.71039 %

Glucose

12.37 g

15.05 g

21.665319 %

Sucrose

13.01 g

16.95 g

30.284396 %

Ovalbumin

11.42 g

12.15 g

6.3922942 %

Water

7.67 g

8.23 g

7.3011734 %

Table 1 represents to the percentage change in each solution. This shows that water diffused in all of the cells, causing them to be in a hypotonic environment.

Graph 1 - Mass Percent Change in Modeling Diffusion and Osmosis

Graph 1 shows the multiple ranges of percent change from the initial weight of the dialysis tubes to the final weight. Notice that all of the solutes had increases in mass, meaning that the

tubes were in hypotonic environments. Table 2 - Data Results Got From Observing Osmosis in Living Cells (Part 2) Solution Color

Initial Weight (g)

Final Weight (g)

Percent Change

Red

0.741 g

0.957 g

29.149 %

Orange

0.725 g

0.634 g

-12.5517 %

Yellow

0.681 g

0.779 g

14.3906 %

Green

0.718 g

0.611 g

-14.9025 %

Blue

0.822 g

0.919 g

11.8004 %

Purple

0.974 g

0.978 g

0.41067 %

In Table 2, the solutions in a hypotonic environment were red, yellow, and blue. Those solutions all 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 mean they were in a hypertonic environment. The purple color could have been either in an isotonic or hypotonic environment, because the initial and final weights were just about the same, but it increased a little bit. Graph 2 - Mass Percent Change in Observing Osmosis in Living Cells

Graph 2 shows the multiple ranges of percent change from the initial weight of the potatoes to the final weight. Notice that the green and orange are decreasing, meaning that they are in a

hypertonic environment. DISCUSSION Based on the results I got for the first part, all of the solutes that were in the tubes had increased by over five percent, with the sucrose having the highest percentage, along with the glucose at twenty-one percent. The lowest increase was the ovalbumin, which increased above six percent. The glucose and sucrose increased majorly because their molecules are hydrophilic and were probably small compared to the other solutes. The ovalbumin probably has larger and more hydrophobic molecules, meaning that the ive transport was fairly longer in time compared to the sugars glucose and sucrose. For the second part, there were three colored solutions that increased, with the red solution having slightly more than twenty-nine percent, yellow with approximately fourteen percent, and blue with around eleven percent. The red solution had the highest increase, possibly because the solution was very hypotonic, since the solution gave the potato more weight than its initial weight. The purple solution did increase, but only a little. This could mean that the purple solution could have been either an isotonic solution or a hypotonic solution. The remaining two colors decreased, meaning that the solutions were most likely hypertonic, because the potato slices had a final weight that was less than the initial weight. The green solution decreased to over fourteen percent, and the orange solution decreased to about twelve percent. My hypothesis for part one, stating that all of the dialysis tubes would be in a hypotonic environment, was proven to be correct. This is because the tubes were placed in a beaker of water. Because there was a higher concentration of water than the solute, this will cause the water to diffuse in the tubing after several days. When water diffuses into a cell, this causes the cell to be enlarged. My hypothesis for the second part, believing that the potato would remain the same size in the warm colored solutions, was proven to be wrong because the solutions in all of

the different colors varied in solute added. This shows that the colors had a different environment in them, with the colors red, yellow, blue, and purple in hypotonic environments, and the colors orange and green in hypertonic environments. This explains that the colors had nothing to do with the gain or loss of weight in the potatoes, but the amount of sucrose or other solution used for them to result in that. Possible errors that my group and I could have made on the experiments would be tying the dialysis tubes incorrectly, inaccurate measuring when gathering the solutions, and the potatoes may have been dried up when one of us sliced them and just left them there instead of putting them in the beakers right away. This experiment relates to the unit we were on, because by observing the cells, we were able to maintain equilibrium or homeostasis by testing cells in an isotonic environment, hypertonic environment, or even a hypotonic environment. We also learned about testing different types of solutes that make a specific cell, such as a potato slice or a dialysis tubing, gain or lose mass percentage, as well.

RESOURCES 1. "Diffusion and Osmosis." HyperPhysics. Web. 4 Jan. 2015. 2. Friedl, Sarah. "Hypertonic Solution." Education Portal. Education Portal. Web. 5 Jan. 2015. 3. "Cellular Processes: Energy and Communication." College Board. College Board. Web. 5 Jan. 2015. 4. "Diffusion and Osmosis." Biology Corner. Biology Corner. Web. 5 Jan. 2015. 5. "Diffusion, Osmosis, and Movement Across a Membrane." Diffusion. The University of Illinois at Chicago. Web. 5 Jan. 2015. 6. "Kinetic Energy." ChemWiki.University of California, Davis. Web. 4 Jan. 2015. 7. Brundage, Adrienne. "Hypotonic Solution."Education Portal. Education Portal. Web. 5 Jan. 2015. 8. Brundage, Adrienne. "Isotonic Solution."Education Portal. Education Portal. Web. 4 Jan. 2015.