Purpose:
1A- In part 1A, we tested to measure the diffusion of small molecules, glucose and starch to be more specific, through dialysis tubing, which is an example of a selectively permeable membrane. In this experiment, the only variable we would have control over would be in the amount of solution in the beaker and in the dialysis bag. We would not have control over the permeability of the bag, or how much solution would or wouldn't pass through. Then depending on significant color change, we would be able to detect the presence in substances different from what was originally in the two closed solutions at the beginning of the lab.
1B- The purpose of this lab is to use the dialysis tubing to the determine the relationship between the solute concentration (sucrose) and the water movement through the process of osmosis. In the lab, the control variable is only the concentration of the solution in the dialysis bag and the beaker. The percentage change in mass of the dialysis tube is depended on how long the dialysis tube have been sit in the beaker. Over time, this will cause the dialysis tube to increase or decrease. In this lab we are trying to find out if the mass of the dialysis tube increase or decrease when it have been sit in the beaker for a period of time.
1C- the purpose of this lab to find out the water potential of potato cylinders. We used a potato to cut 5mm potato cylinders and weighed them. We then put them in a sucrose solution and let them sit over night. The next morning we took them out of the sucrose solution and weighed them again. We took the difference in weight and found the percentage of change.
Introduction:
1A-Diffusion occurs when a substance attempts to equalize. The concentration gradient that a substance will always follow in diffusion is the movement from a high concentration gradient to a low concentration gradient, until equilibrium occurs. For example, if a cell is placed into a solution that has a higher percentage of water in the solution than inside the cell, water will move into the cell until there is an equal percentage of water both inside and outside of the cell. But sometimes a membrane will only allow certain molecules to pass through it; this is called a, as the function states, selectively permeable membrane. In addition, a Benedict's test is used in testing for the presence of glucose. Should a strip change color when submerged into a solution, that would signify that a solution contains glucose within it. A cell membranes permeability is determined by pores in the membrane itself. Depending in the size of the pores in the membrane Denise which molecules can or can't pass through. If a molecule is larger than the openings of the pores in the membrane then it will not be able to pass through.
1B-The process of osmosis occur when water need to move from lower solute concentration to a higher solute. In simple term, when there is more stuff in or outside of the cell, water tend to move to the area that have more stuff. This process is very crucial to determine the balance of cell and it environment or the death of a cell. Osmosis consist of three different type of environments: isotonic, hypertonic, and hypotonic. In isotonic solution, the stuff outside the cell is equal to the stuff inside the cell. In the case of the animal cell, the cell under this condition is stable. Unlike animal cell, plant cell become shriveled and cause the plant to not standing upright. In hypertonic solution, there is more stuff outside than inside the cell. This would cause the water to leave the cell faster than it can enter into the cell. Both plant and animal cell under this condition will die. In the hypotonic solution, there is more stuff inside the cell than outside the cell. Water in this solution will enter the cell faster than it can leave the cell. The animal cell is unstable in this solution and eventually it will burst. With a lot of water rushing into the cell, the plant cell benefit from this solution in that the cell will become more turgid and the plant will stand upright. In this lab, we would expect the potato core to increase in mass under the hypertonic solution and decrease in mass under the hypotonic solution.
1C- Water potential is when a molecule with a lot of water give up water to its surroundings to try creating an equilibrium state. Water potential occurs becuase of two reasons, one reason is when the pressure raises the water potential and the relative concentration of the solute. The pressure rises because if water leaves the cell the the cell will shrink and if the water enters the cell the cell will explode.
Methods:
1A-Diffusion occurs when a substance attempts to equalize. The concentration gradient that a substance will always follow in diffusion is the movement from a high concentration gradient to a low concentration gradient, until equilibrium occurs. For example, if a cell is placed into a solution that has a higher percentage of water in the solution than inside the cell, water will move into the cell until there is an equal percentage of water both inside and outside of the cell. But sometimes a membrane will only allow certain molecules to pass through it; this is called a, as the function states, selectively permeable membrane. In addition, a Benedict's test is used in testing for the presence of glucose. Should a strip change color when submerged into a solution, that would signify that a solution contains glucose within it.
1B- To set up the lab, the six dialysis tube need to be fill with six solution of different concentration of sucrose. Before doing anything else, the initial mass of the tube need to be weighted. The dialysis tube then need to be place in a beaker that have the same concentration of sucrose. In the next step, the dialysis tube need to be sit in the beaker for 30 minute. After the dialysis tube have been sit for 30 minute, the dialysis tube need to be weight to see if there have been a change in mass of the dialysis tube.
1C- We started out by cutting long cylinders out of the potato with a cork borer. We did this twenty-four times to have 4 chunks for each solution. Then we weighed the mass of groups of four and recorded it, so that later we could see if any diffusion/change occurred. We put the groups of 4 into the sucrose solutions (ranging from distilled water to 1 M of sucrose) and covered them with plastic to prevent any evaporation. We let it sit for thirty minutes so that the sucrose could diffuse from the solution. After that, we took the potato chunks out and weighed them once more to see how much they changed. We recorded the weight change as well and calculated the percentage change. This let is see how much solution diffused in or out of the potato.
Data:
Graphs and Charts:
Discussion:
1A-For this part of the experiment, we only had to fill out a chart with whether or not glucose was present and the color of the solution. We were able to find out that after waiting 30 minutes for the diffusion to happen, glucose was present inside AND outside the bag. We tested this out by using Benedict's solution (which is very accurate). The validity of our results is also very high because we discussed as a class what the results for the chart we're supposed to be. Because of that, we compared out graph to what was up posed to be correct and found no inconsistencies with our data. We were also sure of this because our results also made sense; it was what we had predicted would happen. Because there was diffusion of glucose out of the bag, since the membrane was selectively permeable, it was only appropriate that the outside solution would test positive for glucose. We could always have more trials for more accurate results, but since it was easy to test, our results were accurate and fit our hypothesis.
1B-The data stable showed that the more molarity the solution has, the more mass the bag gained. It was pretty constant throughout the experiment that this trend followed. The only outliers were the .2 M and the 1 M solutions. Both the data table and the graph show that these sections don't seem to fit because if the dramatic drop in weight. Also, it doesn't fit our hypothesis that they should gain, not loose, weight as the molarity increases. We think something might've gone wrong with those bags which is why we try to use the class data to compare its validity. Obviously our section brought the class average down, so we can't completely trust that part. However, we can look at other tables' outcomes and compare there. As we predicted, the more the molarity they had, the more it weighed. Even though our experiment came out a little bad, looking at others' results helped conclude that out hypothesis was correct. In the future, more trials of each part would obviously help since ours came out faulty. Also, more time is needed for the bags to be left in the solution for more diffusion to occur.
1C-The data table shows that when there is 0 M (distilled water) to .2 M of sucrose, the solution diffused into the potato cylinders. Once they were in .4 M to 1 M of sucrose solution, the potato cylinders diffused starch out to the solution. This is proven by the data because the percent change in mass is positive from 0-.2 M of sucrose and negative from .4-1 M of sucrose. This make sense because more concentration in the solution means more diffusion will have to occur to reach equilibrium. The data table shows that there is a consistent decrease in percent change in mass up until the .8-1 M of sucrose. It might just be a kink in the solution, but other than that the data is pretty accurate. The higher concentration the solution is, the more diffusion will occur to reach equilibrium. This supported our hypothesis that higher water potential want to go to lower water potential. We also know this data is valid because our percentages were very close to the class average. It would be more valid if we had more trials for each concentration of the sucrose solution and if we let the potato cylinders sit in the solutions a lot longer than thirty minutes. Overall, it was a successful experiment.
Conclusion
1A- in our experiment, the goal was to measure the diffusion going on between the starch solution in the dialysis tubing and the surrounding water. As seen in our chart, after we tested each solution with a Benedict's test , the mix of iodine and distilled water entered the bag while the glucose/starch solution left the bag. We knew this because of the different colors it turned according to whether or not there was glucose present in each solution which there was at the end because some of the solution inside the bag left and was able to bypass the membrane.
1B- In the experiment we concluded the higher the molarity of a substence the greater the osmosis. When plotting the points on our graph we found out that we had two points wrong compared to the class average. We believe they were wrong because we didnt let them sit in the water long enough.
1C- We wanted to prove that water will move from an area of higher water potential to one with lower water potential. Therefore, the lower the concentration of sucrose solution, the more it will diffuse into the potato cylinders. Our data supported this seeing as the percent change in mass is positive from 0-.2 M of sucrose and negative from .4-1 M of sucrose.
Onion Cell Plasmolysis (1E):
Purpose: The purpose of this lab is to investigate what happen to onion cell is put in the hypotonic, isotonic, and hypertonic.
Hypotonic:
In a hypotonic solution, water enter the cell faster than it can leave. This is to the fact that there is more solute inside the cell than outside the cell. Because to this, the size of the cell expand. In an animal cell, the cell would explode. Since this is the onion cell, the onion would become turgid and tough. Hypotonic solution is most suitable to plant like onion.
Isotonic:
In this solution, the amount of water that enter and leave the cell is equal. Because there is no excessive in water entering the cell, the onion cell actually wilt. This mean that the onion is not as turgid as the cell in the hypotonic solution.
Hypertonic :
In this solution, the water leave the cell faster than it can enter the cell. This happen because there is more solute outside the cell than inside the cell. Through the process of osmosis, the water leave the cell. The hypertonic solution is not very suitable for the onion cell. Because so much water is leaving cell, the onion cell significantly shrink in size that there isn't much content left in the cell and the cell die.
