Work in groups of 3. Cut 10 cm of dialysis tubing and soak it in water for 5 - 1
ID: 97859 • Letter: W
Question
Work in groups of 3. Cut 10 cm of dialysis tubing and soak it in water for 5 - 10 minutes until it is pliable. Tie off one end of the tubing tightly with string to form a bag. To open the other end of the bag, rub the end between your fingers until the edges separate. Place 5 - 10 mL of 15% glucose/1% starch solution in the bag. Tie off the other end of the bag, leaving sufficient space for the expansion of the contents in the bag. It is imperative the bag not leak! Record the color of the solution in Table 3. The filled bag will serve as a model of a cell. Fill a 250-mL beaker two-thirds full with the distilled water. Add approximately 4 mL of IKI solution to record the results in Table 3. Immerse the bag in the beaker of solution. Allow your setup to stand for approximately 30 minutes or until you see a distinct color change in the bag or in the beaker. Record the final color of the solution in the bag, and of the solution in the beaker, in Table 3. Which substances move in or out of the membrane and what experimental evidence supports your answer? Which substances do not move in and out of the membrane and why? Explain the results you obtained. Include the concentration differences and membrane pore size in your discussion. Based on your observations, rank the following by relative size, beginning with the smallest: water molecules, IKI molecules, membrane pores, starch molecules. What results would you expect if the experiment started with an IKI solution inside the bag and only starch and water outside? Why? How can you tell if osmosis occurred in the cell model? What are the two main factors in the above activity that influence movement of materials? Predict the change to the rate of movement of materials if you stirred the extracellular solution. Why do you predict this? Predict the change to the rate of movement of materials if you heated the extracellular solution. Why do you predict this?Explanation / Answer
1) glucose and iodine moves in and out of the membrane as the concentration of glucose has changed and the presence of iodine after 30 minutes.
2) starch. it is nonpermeable to the membrane.
3) pore size allows the glucose and iodine molecule to pass through it but did not allow the starch like big molecule to pass through it.
4) water, IKI molecule, membrane pore and starch molecule.
5) outside we will get coloured solution because IKI solution will go outside and reacted with starch solution.
6) the amount of the solution in the bag will be increased.
7) semi permeability and concentration .
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