Lab 6: Diffusion and Osmosis

Student Name:

Course ID/Section: Date:

Answer the questions and report your data in this fillable PDF using the observations and results you recorded in your lab manual while performing the experiments. Save the completed PDF file with your last name and lab number and submit the report as directed by your instructor. (For example: jones_lab6.pdf)

Consider the Concepts1. Explain the difference between the following three terms: solution, solvent, and solute.

Part 1: Diffusion Through a Membrane

2. Based on your results from this experiment, select all the molecules that diffused through the membrane during the one-hour incubation. Select all that apply.

GlucoseStarchWaterLugol's solution

3. Based on YOUR data alone, describe the relationship between the size of a molecule and its ability to diffuse through dialysis tubing membranes.

4. Consider all the solutes inside the dialysis bag "cell" and outside the external solution. At the beginning of the experiment, select the ONE choice that best describes the medium (external solution):

isoosmotic to the cellhypoosmotic to the cellhyperosmotic to the cell

5. At the end of the experiment, did your analysis indicate that some glucose remained inside the dialysis bag? If so, why? If not, why not?

Part 2: Determining Direction of Osmosis6. Using your experimental data, provide the exact change in volume inside each bag, from the initial

10 mL to after osmosis was allowed to occur. Note: If the volume increased, write plus and the amount, if it decreased, write minus and the amount.

Bag #1: mL

Bag #2: mL

7. Did sucrose diffuse through the dialysis tubing? How do you know?

8. For bag #1, compare all the solutes inside the dialysis bag "cell" and outside in the external solution. At the beginning of the experiment, select the ONE choice that best describes the interior of the cell:

isotonic to the mediumhypotonic to the mediumhypertonic to the medium

9. For bag #2, compare all the solutes inside the dialysis bag "cell" and outside in the external solution. At the beginning of the experiment, select the ONE choice that best describes the interior of the cell:

isotonic to the mediumhypotonic to the mediumhypertonic to the medium

10. At any point during the experiment do you think that either bag became isotonic to the external solution? If so, when? If not, why not? How would you demonstrate your assumptions?

11. After studying how a dialysis bag changes in response to different osmotic conditions, some students believe a dialysis bag is more similar to an animal cell, while others consider it more similar to a plant cell. Decide which type of cell you believe is most similar to a dialysis bag and explain your selection in terms of osmosis and osmotic pressure.

Part 3: Tonicity and the Plant Cell12. What types of potatoes did you use in your experiment?

13. In your experiment, what was the exact CHANGE in volume inside each potato strip from the initial volume (initial water displaced) to after osmosis was allowed to occur (final displacement)? Note: If the volume decreased, write minus and the amount.

Potato 1 in water: mL

Potato 1 in salt solution: mL

Potato 2 in water: mL

Potato 2 in salt solution: mL

14. Looking at ONLY the experimental results for your first potato type, select the choices that correctly describe the interior of the potato cells at the beginning of the experiment. Select all that apply.

isotonic to pure waterhypotonic to pure waterhypertonic to pure water

isotonic to 20% NaClhypotonic to 20% NaClhypertonic to 20% NaCl

15. Looking at ONLY the experimental results for your second potato type, select the choices that correctly describe the interior of the potato cells at the beginning of the experiment. Select all that apply.

isotonic to pure waterhypotonic to pure waterhypertonic to pure water

isotonic to 20% NaClhypotonic to 20% NaClhypertonic to 20% NaCl

16. In part 2, you measured osmosis using individual dialysis bags that each represented a single cell. Describe how the potato strip experiment is different.

17. Describe how your results for this experiment would be affected if you had cut the potato slices in advance and left them sitting on the cutting board for several hours before starting the experiment. Be specific about the difference you would expect in your measurements of initial and final potato cell volumes.

Experiment Photographs18. Paste up to four photos of you with your completed lab experiments as directed by your instructor. To upload photos, click inside an empty square below and select your photo file.

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