Diffusion Through A Membrane Lab Conclusion Essay

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Introduction
All cells contain membranes that are selectively permeable, allowing certain things to pass into and leave out of the cell. The process in which molecules of a substance move from an area of high concentration to areas of low concentration is called Diffusion. Whereas Osmosis is the process in which water crosses membranes from regions of high water concentration to areas with low water concentration. While molecules in diffusion move down a concentration gradient, molecules during osmosis both move down a concentration gradient as well as across it. Both diffusion, and osmosis are types of passive transport, which do not require help.
When the concentration of the environment outside of the cell is lower than the inside…show more content…

Results
The potato cores started to decrease in weight as the molarity went up. The potatoes that gained weight were the potatoes placed in deionized water, and the sucrose solution molarity of 0.1.
However, the potatoes started losing weight in the sucrose solution of 0.2 and up.
Sucrose Molarity 0 M 0.1 M 0.2 M 0.3 M 0.4 M 0.5 M 0.6 M
Final Weight (g) 5.1g 5g 4.7g 4.5g 4.2g 4.1g 4.2g
Initial Weight (g) 4.4g 4.5g 4.4g 4.3g 4.4g 4.5g 4.4g
Weight Change (g) 0.7g 0.5g -0.3g -0.2g -0.2g -0.4g -0.2g
% Change in Weight 15.9g 11.1g -6.82g -4.65g -4.55g -8.89g -4.55g

Table 1:

Discussion
When the potato gains weight it was in a hypertonic solution, and when the potato loss weight it was in a hypotonic solution. If the potato would not have changed weight it would have been an isotonic solution, but that was not the case in this experiment. The potato either gained, or lost weight. This data therefore supports the hypothesis that the potato that would be more hypertonic to the sucrose solution and would gain weight, whereas the potato would be hypotonic to the solution and would lose weight. Based on the data from the graph, the osmolarity of the potato was 0.4 M. Osmolarity is the molar concentration of when there is no change in the weight of the potato. In

Diffusion Lab

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Diffusion Lab

Problem
Will starch, water, glucose, iodine or a combination of the above diffuse across the membrane of the dialysis bag causing the bag to either expand or shrivel?

Hypothesis & Strategy
I believe that the smaller molecules, such as glucose and water will diffuse through the dialysis bag’s membrane causing it to expand, due to the concentration gradient. I would test this hypothesis by filling the bag with a solution consisting of water, glucose and starch, tie it off and weigh it. I would then place the bag in a beaker of water and let it sit for a day. Then I would reweigh the bag.

Materials
·     Dialysis Tubing
·     Glucose Starch Solution, 15mL
·     IKI Solution, 5mL
·     4 Glucose Indicator Strips
·     1 Graduated Cylinder
·     1 Plastic Cup, 250mL

Experimental Procedure
1.     Pour 15mL prepared glucose/starch solution into the graduated cylinder.
2.     Get a piece of tubing and use a sting to tie a knot on one end of the tubing.
3.     Open the tubing and pour 15mL of the glucose/starch solution into the tubing.
4.     Determine the initial glucose content in the tubing by using the glucose indicator strip. Record the data in Table 1.
5.     Tie another not at the other end, leaving room for expansion
6.     Record the color of the solution in the bag in Table 1.
7.     Fill a 250mL beaker approximately 2/3 full with distilled water. Add 5mL of iodine to the beaker.
8.     Record the color of the solution in Table 1.
9.     Determine the beaker glucose content using the glucose indicator strip and record the data in Table 1.
10.     Completely immerse the dialysis bag in the solution in the beaker.
11.     Wait at least 30 minutes or until there is a noticeable change in the color of the solution in either the beaker or the dialysis bag.
12.     Remove the dialysis bag from the beaker reweigh it and record the final color and glucose content of the dialysis bag and the beaker. Record this data in Table 1.
13.     Wash your hands and clean up lab area.






Observations

     Color          Glucose Content          Bag
Time     Dialysis Bag     Beaker     Dialysis Bag     Beaker     Weight
Start     Cloudy white     Gold     500 mg/dl     Negative     49.5g
After 30 minutes     Cloudy Purple     Clear     100 mg/dl     100 mg/dl     50.9g




Analysis
1.     What do your observations tell you about the presence of glucose, starch, and IKI in the dialysis bag and the beaker before and after the experiment?
Before the experiment the dialysis bag had water with glucose and starch dissolved in it, while the solution in the beaker consisted of water and iodine. After the experiment the iodine had diffused into the bag while the glucose had diffused out of the bag. This is evident because at the conclusion of the experiment the bag was purple due to the reaction of iodine and starch.

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Diffusion Lab         Starch Solution         Glucose         Strip         Indicator         Cylinder         Record         Knot        




The glucose content of the beaker was higher at the end of the experiment than in the beginning, proving that the glucose had diffused into the beaker from the bag.
2.     What can you conclude about the permeability of the dialysis bag membrane? Which compounds were able to diffuse through the membrane? Which were not? Why were only some able to pass through?
The dialysis bag’s membrane was a selectively permeable membrane. Iodine, glucose and water were able to diffuse through the membrane while starch was not able. This occurred because while iodine, water and glucose molecules are small enough to diffuse through the membrane, disaccharides like starch are too large to diffuse through the membrane.
3.     Was there more or less water in the dialysis bag at the conclusion of the experiment? Why?
There was more water in the bag at the conclusion of the experiment because there was a higher concentration of water outside the bag than inside, creating a concentration gradient.
4.     Why did you weigh the bag? Did the weight increase or decrease? What does this prove?
We weighed the bag so that we would know if there was any increase in weight or water in the bag at the conclusion of the experiment. The weight increased. This proves that the bag’s membrane was selectively permeable.

Conclusion
After doing the experiment I could clearly see that the iodine moved in to the dialysis bag, and some of the glucose move out of the bag to be at equilibrium. We found this out because of how the test strips came out positive for the solution inside the beaker.



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