Diffusion Lab

1A;

The purpose of this experiment is to test the permeability of glucose and starch through a selectively permeable membrane. The inside of the bag has a higher concentration of glucose, and because of diffusion some glucose will go outside of the bag, where there is a lower concentration.

Glucose is a monosaccharide, which means its particles are small enough to pass through a selectively permeable membrane without assistance. Because of this, diffusion of glucose will occur from areas of high concentration to low concentration. The solution's ultimate goal is to reach equilibrium, where the outside and inside of the membrane are at equal concentrations of solute. However, large particles like polysaccharides will be unable to pass through a selectively permeable membrane without facilitation. Starch is a polysaccharide of long chains of glucose.

We filled a bag of dialysis tubing with 15mL of a solution of 15% sucrose and 1% starch. This was put in a cup of water 4 ML of iodine. We let the bag sit the water for about 30 minutes before removing the bag. After letting it sit we tested for the presence of glucose in both the bag and cup.

This is what the diaylsis of the solution looked inside the cup of water and iodine.

This is the data table used to collect date in the experiment.

Before the bag went into the water, we tested the water for starch and glucose. It tested negative for both. Afterwards, the water stayed orange, which showed that no starch left the bag, while glucose was found to be present in the solution. This outcome supported what we know about diffusion because since starch didn't pass through the membrane into the water, it shows that it is a particle too large to pass through. The presence of glucose in the solution from the bag after 30 minutes shows that its structure is small enough to pass through a selectively permeable membrane. It could have been improved if we made sure that the bag was sealed as tightly as possible so that movement of particles was purely from diffusion and not seeping out of the top of the bag.

We concluded that glucose could pass through the membrane. Starch on the other hand is unable to do so and stays on the side of the membrane it started on.

1B:

The purpose of this experiment is to test the osmosis of water in different concentration gradients of sucrose, to see if sucrose can pass through the membrane and the osmosis of water at different concentrations of solute.The independent variable is the amount of sucrose in the bag at the start, and the defendant variable is the percent change of the bag after 30 minutes. 

In this experiment we know that the dialysis bag has a semi-permeable membrane, which means sucrose cannot go through the bag. The only thing that can go through the bag is water so when the weight of the bags change it shows how much water went and out of the bag. When water goes in and out if a membrane it is called osmosis.

We created 6 bags made out of dialysis tubing that were each about 30 cm each. After we cut them we each filled them with a substance of either distilled water, 0.2 M sucrose, 0.4M  sucrose, 0.6 M sucrose, 0.8 M Sucrose, and 1 M Sucrose. After filling the bags we measured the mass of each of them. After closing the bags with rubber bands, we placed all of them in their own cup full of water. We let the bags sit for 30 minutes and after taking the bags out of the water we massed the bags again.

This is a picture of the sucrose solution inside the cup of distelled water.

Here is the data table we used to find both masses for the dialysis bags before and after the experiment plus their mass difference. 

Here is a graph showing the change in mass difference with the dialysis bags.

The reason we calculating percent changes was because they can be easily compared to other tests without having all the initial masses be the same. After looking at the class data we can see that their is a direct relationship between the mass and molarity, because as the molarity of the solution went up the mass difference increased as well. f each of bags were placed in a 0.4 M Sucrose instead of distilled water, the mass differences would change because sucrose would not be able to pass through the semipermeable membrane of the bag. The mass difference for the 0.2M and 0M bags would increase since the solution would be hypotonic. The mass difference for the 0.4M would become zero, because the solution would be isotonic. The mass difference for the 0.6M, 0.8M, and 1M would decrease since the solution was hypertonic.  

1C:


We first filled up 6 different cups with each different solutions (0M, 0.2M, 0.4M, 0.6M, 0.8M,1M). Then by using a cork borer we cut out 4 potato cores for each cup of solution (so 24 potato cylinder in total). Before putting the cores in the solutions we first took the mass of the four cores together. After letting the potato cores soak overnight in the solutions, we dried off the potato cores and then weighed them together.

Here are the potato cores in the 0M, 0.2M, and 0.4 solutions. Notice how they are on the bottom of the cup.

Here are the potato cores in the 0.6M, 0.8M, and 1M solutions. Notice that the potato cores are all floating.

Here is the data from when we massed the potato cores before putting them in the solutions and the mass after they were soaked in the solution overnight. 

Here is the graph representation of the decrease or increase in percent in mass of the potato cores.
1E:


Plasmolysis occurs when water rushes out in a hypertonic solution around a plant cell. As water rushes out of the plant cell the cell shrivels. The cell wall separates from the membrane and the cytoplasm even begins to shrink inside. In the onion cell, this process if plasmolysis occurred because far more water was outside than in the cell. As a plant cell, the rigid cell walls like to be in a hypotonic solution to bear pressure, but on the opposite spectrum of that causes flaccid es and limpness. If water continues to come out of the cell, plasmolysis will occur. In the onion cell, this process if plasmolysis occurred because far more water was outside than in the cell. As a plant cell, the rigid cell walls like to be in a hypotonic solution to bear pressure, but on the opposite spectrum of that causes flaccid es and limpness. If water continues to come out of the cell, plasmolysis will occur.

Here is an example of plasomysis in an onion cell.

http://www.csun.edu/~aef21890/coursework/695/microscopy/microscopy.htm