Lab Write Up A: Diffusion
Aim/Question: In a plasma membrane where the net movement of molecules move from higher concentration to lower concentration, will the dialysis bag turn blue because of the diffusion of glucose and IKI into the dialysis bag?
Hypothesis: If I added the glucose and IKI into the the distilled water, I hypothesize that the water with the IKI solution will diffuse into the dialysis bag and turn into the color blue.
Objective: The objective of the lab is to see and understand the semipermeable membrane and how the diffusion of molecules from high concentration to low concentration works. By adding the IKI into the water and observing whether or not the IKI will diffuse into the glucose/starch solution is the objective.
Materials: Dialysis tubing, plastic cup, glucose/starch solution, distilled water, iodine-potassium iodide (IKI) solution, dropping pipet, glucose test strips, beaker.
Test two locations: the dialysis bag and the cup. Test two solutions: IKI and glucose/ starch solution. For the data collection, construct a table and in the table show/describe the initial solution color and the final solution color for each. Also indicate the glucose test results, using the + symbol for a positive test result and a – symbol for a negative test result.
Pour 160-170 mL of distilled water into a plastic cup. After perform a Benedict’s test for monosaccharide and record the initial glucose test results in a table. Then add approximately 4 mL of IKI solution to the water, mix well and record the initial solution color in Table 1.
Perform the Benedict’s test for monosaccharide for the glucose/starch solutions and record the data.
Acquire a piece of dialysis tubing that has been soaked in water. Since the tubing is soft and pliable, roll the tubing between your thumb and index finger to open it. With a string tie one end of the tune, forming a bag.
Using a small funnel, pour 15 mL of glucose/starch solution in the dialysis bag and smooth out the top of the bag by running it between your thumb and index finger to let out air. Tie the top end of the bag, but leave leave enough room in the bag for expansion. Record the initial color of the glucose/starch solution in Table 1.
Immerse the dialysis bag in the solution in the cup and make sure the portion of the bag containing the glucose/starch solution is completely covered by the solution in the cup at all times.
While waiting for 30 minutes, complete the following exercise. Create a drawing of your experiment (dialysis bag in the cup) and call it Figure 2. Indicate on Figure the initial locations (insider outside of the bag) of all the kinds of molecules that are available for diffusion through the dialysis membrane. For each of the molecules you list on Figure 2, worse a prediction below your drawing their direction of net (overall) diffusion: into the bag, out of the bag, both into and out of the bag equally, or none (will not diffuse across the dialysis membrane). Give a reason for each prediction.
After 30 minutes, remove the bag from the cup, blot it in paper towel and cut a slit in the bag large enough to insert a dropper to obtain a sample to test. Lastly, fill in the final columns of Table 1.
In the figure 2 drawing, the glucose/starch solution will be inside the dialysis bag, but only the glucose will be able to diffuse across the bag. The starch solution is too big to diffuse across the pores of the dialysis bag. On the other hand, the glucose is small enough to go through the pores. Similarly, water molecules and IKI that are outside the dialysis bag, will easily be able to move in and out of the pores. In order for glucose to reach facilitated equilibrium, it will diffuse out into the cup. Through osmosis, the water molecules move to where there are more concentration to reach facilitated equilibrium.
My hypothesis of the IKI solution added in water diffusing into the dialysis bag, was correct. The experiment for lab A had no conflicts that caused me to revise my predictions.
The data tells me how the starch is bigger than the pore size of the dialysis tubing because there was no sign of starch in the dialysis bag. The data also tells me how the the glucose solution, IKI, and water molecules are small enough to go through the pores of the dialysis bag.
Conclusion: Depending on the how tight the string was tied to both ends of the dialysis bag, would there be an effect on how much IKI or starch would diffuse into the dialysis bag? If the string was tied loose, I think it would allow both the IKI and starch to diffuse into the bag; however if the knot was tight, I think it would have the opposite effect.
Lab Write Up B Osmosis
Aim/Question: Does the difference in how much distilled water there are differ in how much solute concentration there is on the net movement of water molecules through a semipermeable membrane?
Hypothesis: By adding the different amount of concentration of the solution, I hypothesize that there will be a difference in how much solute concentration there are through osmosis.
Objective: The objective is to observe how much solute concentration diffuses through a semipermeable membrane depending on how much molar concentration is used in the lab. By different molar concentration you can see how much of a difference there is.
Materials: Dialysis tubing, plastic cups, distilled water, beaker, sucrose solutions, paper towels, balance, paper weight, calculator.
Complete the following steps for each sucrose solution that you are assigned to test.
Pour 160-170 mL of distilled water into a plastic cup and make sure to label to the cup with the concentration of sucrose that you will test.
Just like lab A, obtain a piece of dialysis tubing that has been soaked in water and roll the tubing between your thumb and index finger. Close one end of the tubing by knotting it or tying it off with string. This will form a bag.
Using a small funnel, pour 25 mL of sucrose solution into the dialysis bag and smooth out the top of the bag by running it between your thumb and index finger to expel the air. Tie off the open end of the bag, but leave enough room in the bag to allow for expansion.
Before recording the mass, remember to dry the bag on paper towels. Record the initial mass in a table (Table 2). In Table 2, you will need to have 5 columns (Contents in Dialysis Bag, Initial Mass, Final Mass, Change in Mass, and % Change in Mass) and 6 rows (one for each Molar Concentration). Make sure to give yourself room to write down all your calculations.
Immerse the dialysis bag in the water in the cup and make sure that the portion of the bag that contains the sucrose solution is completely covered by the water in the cup at all times. The next step is to wait 30 minutes before continuing to the next step.
After 30 minutes, remove the bag from the cup and dry it on paper towels. Mass the bag and record the final mass in Table 2. Finally, determine the change in the mass of the bag and record this data in Table 2.
The change in mass indicates the gain of water of the sucrose solution from the dialysis bag. The percent change in mass is being tested in this experiment. The first variable that could influence the outcome of the experiment is the amount of watervoutside of the dialysis bag because depending on the amount of water there are in the cup, in order for both sides of the permeable membrane to reach facilitated equilibrium, the water water molecules will differ. The second variable would be the amount of air in the dialysis bag because if there’s too much air, the water molecules won’t be able to diffuse into the dialysis bag. Another variable would be how much water was absorbed in the string that has been tied on the top and bottom of the dialysis bag. The bag 0.0M proved to be hypertonic. If the distilled water were to be put in the dialysis bag, it would become hypertonic because the water would diffuse out of the bag to reach equilibrium. Although there were errors in the experiment that could have had an affect on the lab, the outcome that we hypothesized came out to be correct. My results support my hypothesis because with the amount of concentration in each solution, the mass was either big or small. The 0 M setup was supposed to be isotonic, but the results proved to not be true. If the dialysis was filled with water instead of the sucrose solution, the solution would be hypertonic and the dialysis bag would decrease in mass. Drinking seawater can dehydrate the body since the cell will lose water. The seawater has a greater concentration than the cells lining our small intestine. Therefore in order for the cells to reach facilitated equilibrium, the body will lose a lot of water, dehydrating the body.
Conclusion: Would the amount of concentration in a solution eventually affect the change in mass? I think the different amount of concentration changes the mass of the solution left in the dialysis bag. The more concentration in a bag, the more weight it’ll gain.
Lab Write Up C Plant Cells and Water Potential
Aim/Question: How will the different amount of sucrose solution affect the water potential of the potato cylinders?
Hypothesis: Depending on how much solution there is, I think higher the concentration, the more water the potato will lose because it has more water potential.
Objective: The objective is to observe and understand the water potential by immersing the potato cores in the sucrose solutions and determining the change in mass. We are trying to understand which way the water will diffuse through living plant tissues (specifically potatoes).
Materials: Plastic cups, distilled water, sucrose solutions, potato cores (or cork borer, scalpel, and potato), plastic wrap, paper towels, balance, thermometer, calculator.
Label a cup with the concentration of sucrose that you will test.
With the cork borer, cut four cylinders of potato tissue from the potato. Careful not to stab your hand with the cork borer. Cut the potato cylinders approximately 3 cm in length and trim both ends of the cylinder to remove the skin. When slicing the ends, always be careful.
Place the potato cylinder in a beaker or cup and cover them with a lid or plastic wrap.
Use a balance to determine the total mass of all the potato sections. On Table 3, record the initial mass. Your table should have 7 columns (Contents in cup, temp, initial mass, final mass, change in mass, % change in mass and % change in mass class average) and 6 rows (one for each molarity)
After placing all the potato sections in the labeled cup, pour 100 mL of the assigned sucrose solution into the cup.
Cover the cup with plastic wrap.
If you are assigned with a second concentration of sucrose to test, repeat steps 1-6 using the second solution.
Stop. Allow the potato sections to remain in the sucrose solution overnight. Then, proceed to Step 9.
The water potential of the solution at equilibrium is 0+0=0. The water potential of the potato cells at equilibrium is 0. C=mole/Liter. T= 297K. Using the formula, I got (-1)( )(0.0831)(297)= – bars. I would expect the vegetable slices to gain water since the water potential in the vegetable slices are lower inside its cells. Because the water potential is lower, water will move into the slices, allowing it to expand and become hypotonic. I would advise the farm manager to stop irrigating the seawater from the Mediterranean Sea because instead of helping the wheat, it will in fact make the farm dry. Considering the seawater to have a lower water potential than the roots, the wheat will lose more water trying to reach facilitated equilibrium. If a marine clam is mistakenly added to a freshwater aquarium, the cells in the clam, in trying to reach equilibrium, will become hypotonic and burst causing the clam to die. If this procedure took place, the carrot cells will lose water because the syrup is highly concentrated and it will try to balance it out. Since the syrup is low in potential, when it reaches the epidermis of the carrot cell, it will take up all the water in the carrot cells. The carrot cells have a lower potential than the water and it will gain more water. The syrup absorbs the carrot cell’s water causing the carrot to increase in size and causing the level of the water in the cup to rise.
Conclusion: Would the different temperature have an affect on the water potential of the potato cylinders? I think the higher the temperature, there would be more water potential because of how quickly the molecules diffuse in and out of the dialysis bag.