Monday, October 21, 2013

Diffusion-Osmosis Lab

Chau: A
Gunnar: B
Derek: C
Luke: E

Purpose:
1A Diffusion: The purpose of this part of the lab was to test diffusion of small molecules through a selective permeable membrane. We were testing with solution color and the presence of glucose.

1B Osmosis: The purpose of the osmosis portion of the lab was to test the relationship between solute concentration and the movement of water through a selectively permeable membrane.

1C Water Potential: The purpose of this experiment was to gain an understanding of how the molarity of a solute affects the transfer of water in solutions.

1E Plasmolysis: The purpose of the Onion Plasmolysis lab was to examine how highly concentrated solutions affect diffusion and the contents of a cell.


Introduction:
1A Diffusion: The membrane allows molecules to pass through through the process of diffusion. However a selectively permeable membrane only allows some molecules to pass through but not others. Molecules go from a higher concentration to a lower concentration.

1B Osmosis: Osmosis is a process where molecules of a solvent pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane.

1C Water Potential: The term "water potential" refers to the tndency of water to move around from one place to another. In general, water moves from areas of high water potential to areas of low water potential.

1E Plasmolysis: A plant cell, such as the onion cell in the experiment, strives to be at a full state, so that it may retain its structure. It achieves this in a hypotonic solution, but wilts and dies in isotonic and hypertonic solutions respectively. Plasmolysis is when the cell has lost so much water that the cytoplasm inside pulls away from the cell wall and can cause the cell wall to collapse.


Methods:
1A Diffusion: we had the dialysis bag put into the solution of iodine and distilled water for diffusion to occur. before hand we had to prepare the bag using water.

1B Osmosis: We filled six dialysis bags, one with  0 M distilled water and the rest with sucrose solutions of 0.2 M, 0.4 M, 0.6 M, 0.8 M, and 1.0 M and measured the mass difference and amount of percentage change of mass after they soaked in a cup of water for 30 minutes.

1C Water Potential: We measured out equal amounts of distilled water and sucrose solutions of 0.2, 0.4, 0.6, 0.8, and 1.0 molarities into plastic cups. We then hole-boring device to cut cylindrical cores out of our potatoes, and placed four similarly sized cores in each cup. We left these cups to sit overnight so that the osmosis could reach equilibrium.

1E Plasmolysis: We placed the onion cells on a wet mount and placed them underneath a microscope. Then, using a dropper, placed 3 drops of 15% NaCl solution onto the slide, pushing it over onto our cell. After that, we followed the same procedure, only this time using fresh water instead.


Data:
1A Diffusion: The bag solution color was colorless initially and then final it was black. For the presence of glucose the bag had glucose to begin with so ended with having glucose. For the beaker the color was red initially and then lighter red in the end. For presence of glucose it had none to begin with then in the end it had glucose.

1B Osmosis: After the bags soaked in cups of water for 30 minutes they had fairly significant mass differences and thereby significant percent changes in mass. The bag with 0 M distilled water had a loss of mass and negative percent change in mass while the dialysis bags with sucrose in them from .2 M and up gained mass and increase in percent changes in mass. 

1C Water Potential: The masses of the potato cores in the distilled water increased overnight by a good amount, and the mass of the cores in the 0.2M sucrose increased as well, if less so. However, the cores in the rest of the cups saw a decrease in mass, with the severity of the mass decrease being bigger in solutions with higher concentrations.

1E Plasmolysis: before the application of the NaCl solution, the onion cells were mostly a bright pink/red color. When we used the solution, the shade of the cell grew darker, and the color retracted from the inner edges of the cell. Using the fresh water, the cell went back to its previous state.


Graphs and Charts:

1A Diffusion:

1B Osmosis:


Dialysis Bag results
Percent change in mass of dialysis bags graph












1C Water Potential:


1E Plasmolysis:
--The top layer shows the regular onion cell, while the bottom shows the plasmolyzed cell.  



Discussion:

1A Diffusion: The results concluded that iodine and glucose were the molecules that went through the process of diffusion to have equilibrium. The bag received the iodine which made its drastic color change while the beaker received glucose.

1B Osmosis: The dialysis bag containing water had a negative mass difference and negative percent change because more water exited the dialysis bag than entered. That occurred because there was a larger amount of distilled water in the bag than out of it, causing the selectively permeable membrane to transfer the distilled water out of the bag, making it lose mass. The dialysis bags with sucrose in them from .2 M and up had positive mass differences and positive percent changes in mass because more water entered the bag than exited. That occurred because there wasn't any water in the bag in the first place, causing the selectively permeable membrane to transfer water inside the bag, making the bag gain mass.

1C Water Potential: The increase in mass of the potato cores in the water and low-concentration sucrose was due to a higher water potential in those solutions. Because the water potential in the potato cores was less than that of the solutions they were submerged in, the water moved into the cores and their masses increased. When the molarity of the sucrose began to reach higher than 0.2M, however, the water potential of the cores ended up being higher than that of the solutions, so the water moved out of the cores, causing the drop in mass.

1E Plasmolysis: The application on the NaCl solution created a hypertonic environment, causing the cell to lose water and convert to a plasmolyized state. The water inside of the cell flowed out into the solution in order to balance out the NaCl to Water ratio and reach equilibrium. When we poured fresh water back into the cell, the process was reversed and a hypotonic environment was created. The cell reverted back to being full, as the greater concentration of water on the outside of the cell proceeded to flow back.


Conclusion:

1A Diffusion: We found out that starch was not one of the molecules that passed through the membrane and that glucose was the one that was allowed through the selectively permeable membrane.

1B Osmosis: In conclusion it can be determined that if water and another solution differ in concentration and are separated by a selectively permeable membrane, water will move between the membrane until both sides contain equal amounts of water.

1C Water Potential: Looking at the results of our experiment, it can be concluded that higher solute concentrations result in lower water potential, which causes the water to move into those solutions with high solute.

1E Plasmolysis: These results confirm that a hypotonic solution allows a plant cell to retain its turgidity and live, while the hypertonic solution causes it to lose water and become inneffective. DETRITUS!



References: N/A