Answer 2 - hypotonic is distilled water, hypertonic is 6% NaCl, isotonic is 0.9% NaCl

Prof. Smith: Excellent! This means that if we place cells (plant or animal cells) in these three different solutions (hypotonic, isotonic, hypertonic), we might expect a structural change depending on osmosis (water movement) in or/and out of the cell. This is the practical for today!

You begin with plant cells, specifically onion cells. You need to prepare microscope slides of inner onion epidermis in the three solutions and observe under the compound microscope. 

You are provided with the following to begin preparing your samples:

1. Onion

2. Three plastic pipettes

3. Compound microscope

4. Microscope lens cleaning supplies (lens paper, lens cleaner)

5. Microscope slides and coverslips

6. Tweezers

7. Marker

The three solutions: distilled water, 0.9% NaCl, 6% NaCl

You follow the steps below:

1. Use a glass slide and add a small piece of the inner onion epidermis that you professor will provide. Add a drop of distilled water and carefully use a cover slip to cover on top (avoid trapping air bubbles, this will affect what you can observe under the microscope!). This is slide 1.

2. Prepare a new glass slide with the same procedure as step 1, but instead add 0.9% NaCl solution. Wait for 5 minutes and then add the cover slip. This is slide 2.

3. Continue to prepare slide 3 with the same procedure as step 2, but instead add 6% NaCl solution.

4. Examine slides 1,2 and 3 separately under the compound microscope starting at lower magnification and focus. Move to higher magnification and focus on one cell. Identify the shape, the plasma membrane and the cell wall.