Cell Membrane Transport

12 Jun Cell Membrane Transport

Question
Cell Membrane Transport

Exercise 1 – Diffusion through an Artificial Membrane

Data Table 1 – Changes during Dialysis

Color

Before Dialysis

After Dialysis

Solution in Dialysis tubing

Solution in Cup 1

Data Table 2 – Benedict’s test Results

Tube Contents

Color Before Heating

Color After Heating

#1 IKI solution from cup 1

#2 Dialysis bag solution from cup 2

#3 Distilled water

Questions:

1. Which of the tubes #1, #2, or #3 is the control for this experiment?

2. What color change did you observe inside the dialysis tubing? What does that change indicate?

3. Was there a color change in the water surrounding the tubing? If so, explain.

4. What color change(in the liquid) was observed in the water containing the IKI after heating? What does that change indicate?

5. Did you notice any precipitate in the tubes after heating? If so, what color was it? Which tubes was it present in?

6. What does the Benedict’s reagent detect?

7. What does the IKI solution detect?

8. Is the transport mechanism observed here passive or active? Why?

Exercise 2 – Diffusion at Different Temperatures

Data Table 3 – Diffusion of KMnO4 at Various Temperatures

Temperature inside cup

Color of water

0 minutes

5 minutes

#1 Cold _______________

#2 Ambient ________________

#3 Hot ________________

Questions:

1. State a general hypothesis to cover how temperature affects rate of diffusion.

2. Did all of the solution in the tubes change color within 5 minutes? If so, which tubes?

3. If you had any tubes that did not change color within 5 minutes, how much longer would you speculate it would take to change colors? Explain your answer.

4. Do you think if the test tubes were larger and held more water the results would be the same? Explain your answer.

5. How does temperature affect the rate of diffusion?

Exercise 3 – Tonicity and Diffusion

Data Table 4-Potato Dimensions

Tubes of Potato

Potato Weight Before Osmosis

(grams)

Potato Weight After Osmosis

(grams)

Weight Change

(grams)

#1 Distilled water

#2 10% Sodium Chloride

Using the information from Data Table 4, fill in the following chart. Describe the tonicity for the potato cells compared to each tube solution and describe the tonicity of the tube solutions compared to the potato cells. Which is isotonic, hypertonic, or hypotonic and how did the water move? (into the cell, our of the cells, no water movement)

Tubes of Potato

Hypotonic, Hypertonic, or Isotonic

Describe the movement of water

Potato

Tube contents

#1

#2

Questions:

1. What is the condition of each potato strip after soaking in the test tubes for an hour? Which one is limp and which one is crisp?

2. How would you explain the difference in the conditions of the potato strips using the concept of tonicity?

3. How do the changes in the conditions of the potato strips relate to the wilting of plants?