BIO 120L Module Three Lab Report – Diffusion and Osmosis

11 Jun BIO 120L Module Three Lab Report – Diffusion and Osmosis

Question
BIO 120L Module Three Lab Report: Diffusion and Osmosis

Experiment 1: Diffusion Through a Liquid

After completing this experiment, record your data in the tables below (Tables 1 and 2).

1. Based on the background information provided regarding the two dyes and general properties of diffusion, make your prediction about how the diffusion rates of the two dyes will differ.

2. Next, propose a specific method to test your prediction.

Table 1: Rate of Diffusion in Corn Syrup

Time (sec.) Blue Dye Time (sec.) Red Dye

10 10

20 20

30 30

40 40

50 50

60 60

Table 2: Speed of Diffusion of Different Molecular Weight Dyes

Structure Molecular Weight Total Distance Speed of Diffusion (mm/hr.)*

Blue Dye

Red Dye

* Multiply the total distance diffused by 60 to get the hourly diffusion rate.

3. Which dye diffused faster? Did this support your initial prediction? Why or why not?

4. Does the rate of diffusion correspond with the molecular weight of the dye?

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Experiment 2: Diffusion—Concentration Gradients and Membrane Permeability

After completing this experiment, record your data in the tables below (Tables 3 and 4).

Table 3: Indicator Reagent Data

Indicator Starch Positive Control (Color) Starch Negative Control (Color) Glucose Positive Control (Color) Glucose Negative Control (Color)

IKI Solution

Glucose Test Strip

Table 4: Diffusion of Starch and Glucose Over Time

Indicator Dialysis Bag After 1 Hour Beaker Water After 1 Hour

IKI Solution

Glucose Test Strip

5. Why is it necessary to have positive and negative controls in this experiment?

6. Which substance(s) crossed the dialysis membrane? Support your response with data-based evidence.

7. Which molecules remained inside of the dialysis bag?

8. Did all of the molecules diffuse out of the bag into the beaker? Why or why not?

9. Does the rate of diffusion change over time? Why or why not?

Experiment 3: Osmosis—Direction and Concentration Gradients

After completing this experiment, record your data in the table below (Table 6).

10. For each bag, hypothesize whether water will flow in or out of each dialysis bag, and provide your reasoning using specific terms from this module.

Yellow:

Red:

Blue:

Green:

Table 6: Sucrose Concentration vs. Tubing Permeability

Band Color Sucrose % Initial Volume (mL) Final Volume (mL) Net Displacement (mL) +/-

Yellow

Red

Blue

Green

11. 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.

12. Which tubing increased the most in volume? Why?

13. What does this tell you about the relative tonicity between the contents of the tubing and the solution in the beaker?

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

15. How are excess salts that accumulate in cells transferred to the bloodstream so they can be removed from the body? Explain how this process works in terms of tonicity.

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

17. 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.

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Experiment 4: Osmosis—Tonicity and the Plant Cell

After completing this experiment, record your data in the table below (Table 7).

Table 7: Water Displacement per Potato Sample

Potato Type Potato Sample Initial Displacement (mL) Final Displacement (mL)—Step 11 Net Displacement (mL)

A

B

A

B

18. How did the physical characteristics of the potato differ before and after the experiment? Did it vary by potato type?

19. What does the net change in the potato sample indicate?

20. Different types of potatoes have varying natural sugar concentrations. Explain how this may influence the water potential of each type of potato.

21. Based on the data from this experiment, hypothesize which potato has the highest natural sugar concentration. Explain your reasoning.

22. Did water flow in or out of the plant cells (potato cells) in each of the samples examined? How do you know this?

23. Would this experiment work with other plant cells? What about with animal cells? Why or why not?

24. From what you know of tonicity, what can you say about the plant cells and the solutions in the test tubes?

25. What do your results show about the concentration of the cytoplasm in the potato cells at the start of the experiment?

26. If the potato is allowed to dehydrate by sitting in open air, would the potato cells be more likely to absorb more or less water? Explain.

27. Explain why in order to achieve optimal health, physicians advise drinking at least eighteight-ounce glasses of water per day. List several ways that this helps the body cells function properly. Why is a diet high in sodium a bad idea when it comes to blood pressure?