Plasmolysis in Elodea Plant Cells

Write all answers in your composition notebook.   Title this Lab, "Plasmolysis in Elodea Plant Cells" in your notebook.

Pre-Lab (Title this Pre-Lab in your notebook)

Visit the following sites and read the information about the Plasma (Cell Membrane):

Life Science Connections (the Cell Membrane)

University of South Dakota- Cell-ebration: Cell Membrane

Answer the following questions in your notebook. 


1. What is the major function of a cell membrane?
2. Why did the first site depict the cell membrane as a gate?
3. Name 5 important terms associated with the plasma membrane.
4. How is the structure of the cell membrane related to its function?

Visit the following site and read the information about the Cell Wall.  

The Cell Wall from Molecular Expressions

Answer the questions in your notebook. 

5. What is the major function of the cell wall?
6. Describe the structure of the cell wall and its composition.
7. How is the structure of the cell wall related to its function?



Experiment and Observations (Write this as the next section in your composition notebook.)

IMPORTANT NOTE!!! When asked to record your observations do the following:

• Draw a sketch of a group of Elodea cells under the described condition. 

Identify/label the condition.

• Label the magnification under which the plant cells are being observed (40x or 100x).

• Label the sketches to note the cell structures that you can identify.

• Be sure to note any changes in the color, size, and shape of the cells.

• Make your sketches as accurate as possible.

Part 1- Elodea in Tap Water

1. 1. Prepare a wet mount of an Elodea leaf with tap water. To do this, place a drop of water towards one end of the slide. Using forceps, remove a small leaf from the tip of an Elodea plant and lay it flat in the drop of water. Cover with a cover slip.
   2. Observe the leaf at 40X and record your observations.
   3.  Increase the magnification to 100X, observe, and record your observations.
   
   

Part 2- Elodea in 5% Salt Solution

1. Remove the slide from the stage of the microscope.
2. Place 2 drops of the 5% salt solution on the slide at the left edge of the cover slip.
3. Tear off a small piece of paper towel and place the torn edge on the slide at the right edge of the cover slip. The piece of towel should begin to soak up water, drawing the salt solution under the cover slip as it does so. (See Figure)
   
4. Return the slide to the microscope stage and observe the cells at 40X and 100X.
5. Record your observations.

Part 3- Elodea in 10% Salt Solution

1. Repeat the procedure above with 10% salt solution.
2. Observe the cells at 40X and 100X. Record your observations.

Part 4- Flushing Out the Salt Solution

1. Remove the slide from the stage of the microscope.
2. Place 3-5 drops of tap water on the slide at the cover slip.
3. Draw the water through using a small piece of paper towel.
4. Observe the cells at 40x and 100x. Record your observations.
5. 
   

Remove the slide from the stage, clean it, and the cover slip, and put it away.

Conclusions   (Write this in your composition notebook.)

       1. Why did the cells shrink in the salt solutions?  Use the terms diffusion, concentration, and membrane in your answer. 

     2. Why didn't the salt from the outside just move inside the cell instead of the water moving out of the cell?  Use the term selectively permeable in your answer

     3. What structure did the shrinking of the cell allow you to observe in better detail? 

     4. Why didn't the cell wall shrink and collapse? 

     5. Predict what would happen if we used a 20% salt solution for an additional part of the lab.

     6. In a sentence or two, relate what we did in this lab to the concept of HOMEOSTASIS.





Adapted from an AAAS Lab