Experiment 2: Osmosis - Direction and Concentration Gradients In this experiment

ID: 39669 • Letter: E

Question

Experiment 2: 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

(3) 250 mL Beakers

(1) 10 mL Graduated Cylinder

(1) 100 mL Graduated Cylinder

Permanent Marker

*8 Rubber Bands (2 blue, 2 green, 2 red, and 2 yellow)

60 g Sucrose (Sugar) Powder, C12H22O11

4 Waste Beakers (any volume)

*Paper Towels

*Scissors

*Stopwatch

*Water

*(4) 15 cm. Pieces of Dialysis Tubing

*Contains latex. Please handle wearing safety gloves if you have a latex allergy.

*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 tubing between your fingers; this will open the tubing. Close one end of the tubing by folding over 3.0 cm of one end (this will become the bottom). Fold it again and secure with a yellow rubber band (use

4. 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.

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 according to the instructions provided on the bottles label (your kit contains 60 g of sucrose in a chemical bottle) . This will create 200 mL of a 30% stock sucrose solution.

8. Use Table 2 to create additional sucrose solutions that are 30%, 15% and 3% concentrated, respectively. Use the graduated cylinder and waste beakers to create these solutions. Set these solutions aside.

Table 2: 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.

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.

13. Verify and record the initial volume of solution from each bag in Table 3.

Figure 8: The dialysis bags are filled with varying concentrations of sucrose solution and placed in one of two beakers.

14. Place the yellow, red, and blue banded tubing in Beaker 2. Place the green banded tubing in Beaker 1 (Figure 8).

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 3.

Data Tables and Post-Lab Assessment

Table 3: Sucrose Concentration vs. Tubing Permeability

Band Color

% Sucrose in Beaker

% Sucrose in Bag

Initial Volume (mL)

Final Volume (mL)

Net Displacement (mL)

Yellow

Red

Blue

Green

Hypothesis:

For each of the tubing pieces, identify whether the solution inside was hypotonic, hypertonic, or isotonic in comparison to the beaker solution in which it was placed.

Which tubing increased the most in volume? Explain why this happened.

What do the results of this experiment this tell you about the relative tonicity between the contents of the tubing and the solution in the beaker?

What would happen if the tubing with the yellow band was placed in a beaker of distilled water?

How are excess salts that accumulate in cells transferred to the blood stream so they can be removed from the body? Be sure to explain how this process works in terms of tonicity.

If you wanted water to flow out of a tubing piece filled with a 50% solution, what would the minimum concentration of the beaker solution need to be? Explain your answer using scientific evidence.

How is this experiment similar to the way a cell membrane works in the body? How is it different? Be specific with your response.

Table 3: Sucrose Concentration vs. Tubing Permeability

Band Color

% Sucrose in Beaker

% Sucrose in Bag

Initial Volume (mL)

Final Volume (mL)

Net Displacement (mL)

Yellow

Red

Blue

Green

Explanation / Answer

Table 3: Sucrose Concentration vs. Tubing Permeability

Band Color

% Sucrose in Beaker

% Sucrose in Bag

Initial Volume (mL)

Final Volume (mL)

Net Displacement (mL)

Yellow

30%

Red

15%

Blue

Green

30%

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.

Ans) Osmosis is the diffusion of a water through a selectively permeable membrane.

If the solution in the beaker is hypertonic, the water comes out of the dialysis bag and the dialysis bag loses the weight (volume decreases).

If the solution in the beaker is hypotonic, the water will inter into the dialysis bag and the dialysis bag gains the weight (volume increases).

If the solution in the beaker is isotonic, the water diffuses into the dialysis bag, but it will not accumulate in the bag, so there will not be any change in the volume of the bag.

The diffusion occurs till it attains equilibrium.

Beaker 1 has 3% sucrose, the yellow band is having 30% sucrose, so the volume will increase inside the bag at a faster rate. The red band which has 15% sucrose, will also increase in volume but a little bit slower rate than yellow bag. The blue band which has 3% sucrose will not change in the volume as the concentration outside and inside is same.

In beaker 2, green band with 3% solution placed in 30% solution in beaker, here the water from bag will diffuse outside, so there will be loss of volume in the bag.

For each of the tubing pieces, identify whether the solution inside was hypotonic, hypertonic, or isotonic in comparison to the beaker solution in which it was placed.

Yellow band - Hypertonic

Red band -Hypertonic

Blue band -Isotonic

Green band -Hypotonic

Which tubing increased the most in volume? Explain why this happened.

Yellow rubber band and red rubber band tubing increased in size, as water tried diffuse inside because of the presence high solute concentration.

What do the results of this experiment this tell you about the relative tonicity between the contents of the tubing and the solution in the beaker?

The results will tell us that water always flows towards higher solute concentration till it attains equilibrium.

What would happen if the tubing with the yellow band was placed in a beaker of distilled water?

When yellow band is place in distilled water, the water try to enter into the bag at a faster rate and volume will increase. (Sometimes the tube may burst also)

How are excess salts that accumulate in cells transferred to the blood stream so they can be removed from the body? Be sure to explain how this process works in terms of tonicity

When excess salts accumulate in body, outside fluid tend to enter into the cell, as cell will be hypertonic. The cell fluid will be diluted, so salts will move out of cell to the blood stream (as it has become less concentrated).

If you wanted water to flow out of a tubing piece filled with a 50% solution, what would the minimum concentration of the beaker solution need to be? Explain your answer using scientific evidence.

We need 100% water in the beaker if we want the water to flow out from the dialysis tube containing 50% solution.

How is this experiment similar to the way a cell membrane works in the body? How is it different? Be specific with your response.

The functioning of cell is important for us and it need specific conditions to function. So maintenance of concentration of fluid outside and inside cell is importance. Any abnormal fluid concentration can make a cell to bulge or shrink or sometimes will make to burst. This are very rare condition. The above study shows us how important the maintenance of solute concentration outside and inside the cell.