Experiment 3 Osmosis Direction and Concentration Gradients In this experiment we will investigate the effect of solute concentration on osmosis A semi permeable membrane dialysis tubing and sucrose will create an osmotic environment similar to that of a cell This selective permeability allows us to examine the net movement of water across the membrane You will begin the experiment with a 30 sucrose solution and perform a set of serial dilutions to create lower concentration solutions Some of the sucrose concentrations will be membrane permeable while others will not be permeable can you determine why this is Materials 60 g Sucrose Powder C12H22O11 3 250 mL Beakers 4 Waste Beakers any volume 8 Rubber Bands two red two blue two green and two yellow 10 mL Graduated Cylinder 100 mL Graduated Cylinder Stopwatch Permanent Marker Water Scissors Paper Towel 4 15 cm Pieces of Dialysis Tubing You must provide Be sure to measure and cut only the length you need for this experiment Reserve the remainder for later experiments Procedure 1 Use the permanent marker to label the three 250 mL beakers as 1 2 and 3 2 Cut four strips of dialysis tubing each 15 0 cm long Fill Beaker 3 with 100 mL of water and submerge the four pieces of dialysis tubing in the water for at least 10 minutes 3 After 10 minutes remove one piece of tubing from the beaker Use your thumb and pointer finger to rub the dialysis tubing between your fingers This will work open the dialysis tubing 4 Wrap one of the yellow rubber bands around one end of the dialysis tubing Leave approximately 1 2 in of tubing below the rubber band Tie a knot in the remaining dialysis tubing just above or just below the rubber band This will create a seal and ensures that solution will not leak out of the tube later in the experiment 2013 eScience Labs LLC All Rights Reserved 5 To test that no solution can leak out add a few drops of water to the tubing and look for water leakage If any water leaks tighten the rubber band and or the knot in the tubing Make sure you pour the water out of the tubing before continuing to the next step 6 Repeat Steps 4 5 with the three remaining dialysis tubes using each of the three remaining rubber band colors 7 Reconstitute the sucrose powder your kit contains 60 g of sucrose in a chemical bottle according to the instructions provided on the bottle s label This will create 200 mL of a 30 stock sucrose solution 8 Use Table 5 to create additional sucrose solutions that are 30 15 and 3 concentrated respectively Use the graduated cylinder and extra beakers to create these solutions Set these solutions aside Table 5 Serial Dilution Instructions Sucrose Solution mL of Stock Sucrose Solution Needed mL of Water Needed 30 10 0 15 5 5 3 1 9 3 1 9 9 Pour 150 mL of the remaining stock sucrose solution into Beaker 1 10 Use some of the remaining stock sucrose solution to create an additional 200 mL of a 3 sucrose solution into Beaker 2 Hint Use your knowledge of serial dilutions to create this final 3 sucrose solution Refer to the Introduction for more information on performing a serial dilution 11 Measure and pour 10 mL of the remaining 30 sucrose solution into the dialysis bag with the yellow rubber band Seal the top of this tubing with the remaining yellow rubber band 12 Measure and pour 10 mL of the 15 sucrose solution in the bag with the red rubber band and seal the top of the dialysis tubing with the remaining red rubber band 10 mL of the 3 sucrose solution in the bag with the blue rubber band and seal the dialysis tubing with the remaining blue rubber band The final 10 mL of 3 sucrose solution in the bag with the green rubber band Seal the dialysis tubing with the remaining green rubber band 2013 eScience Labs LLC All Rights Reserved Figure 4 The dialysis bags are filled with varying concentrations of sucrose solution and placed in one of two beakers 13 Verify and record the initial volume of solution from each bag in Table 6 14 Place the yellow red and blue banded tubing in Beaker 2 Place the green banded tubing in Beaker 1 Figure 4 15 Hypothesize whether water will flow in or out of each dialysis bag Include your hypotheses along with supporting scientific reasoning in the Hypotheses section at the end of this procedure 16 Allow the bags to sit for one hour While waiting pour out the water in the 250 mL beaker that was used to soak the dialysis tubing in Step 1 You will use the beaker in Step 19 17 After allowing the tubing to sit for one hour remove them from the beakers 18 Carefully open the tubing The top of the tubing may need to be cut off removed as they tend to dry out over the course of an hour Measure the solution volumes of each dialysis bag using the 100 mL graduated cylinder Make sure to empty and dry the cylinder completely between each sample 19 Record your data in Table 6 Hypothesis Table 6 Sucrose Concentration vs Tubing Permeability 2013 eScience Labs LLC All Rights Reserved Band Color Sucrose Yellow 15 8 11 3 Red 30 10 11 1 Blue 3 10 11 1 Green 3 10 5 5 Initial Volume mL Final Volume mL Net Displacement mL Post Lab Questions 1 For each of the tubing pieces identify whether the solution inside was hypotonic hypertonic or isotonic in comparison to the beaker solution it was placed in The yellow red and blue tubing pieces were hypotonic compared to the solution The green tubing piece was hypertonic compared to the solution 2 Which tubing increased the most in volume Why The yellow tubing had the most increase in volume I think this is because it had equal parts water and sucrose so there was more room for the solution to flow inside of the bag 3 What does this tell you about the relative tonicity between the contents of the tubing and the solution in the beaker The tonicity of the two were mixed This caused the tonicity of the bag to increase and the tonicity of the solution in the beaker to decrease 4 What would happen if the tubing with the yellow band was placed in a beaker of distilled water It would cause the tubing to burst because it would be trying to equal out the 2013 eScience Labs LLC All Rights Reserved solutions in the bag and in the beaker 5 Osmosis is how excess salts that accumulate in cells are transferred to the blood stream so they can be removed from the body Explain how this process works in terms of tonicity The solution of salts inside the cell are hypertonic to the blood stream so the salts move through the semipermeable membrane of the cell to the less concentrated blood 6 How is