Name: ____________________________

Period: _____

Osmosis in Elodea Cells

Introduction

One of the functions of the cell membrane is to control the flow of materials into and out of the cell. In this investigation, you will observe the effects of placing plant cells in solutions of various concentrations. 

Purpose

To view the process of osmosis and see the effects it has on plant cells.

Materials 

Elodea leaves                        microscope slides                cover slips        

microscope                        distilled water                        tap water

5% salt solution                        10% salt solution                paper towels

Procedure

1. Prepare a wet mount of an Elodea leaf with tap water.

2. Observe the leaf at 40X and record your observations.

3. Increase the magnification to 100X, observe, and record your observations.

4. Remove the slide from the stage of the microscope and place two drops of the 5% salt solution on the slide at the edge of the coverslip. Tear off a small piece of paper towel and place the torn edge on the slide at the edge of the coverslip that is opposite the side where the salt solution was placed. The piece of towel should begin to soak up water, drawing the salt solution under the cover slip as it does so.

5. Return the slide to the microscope stage and repeat the observations of the cells at 40X and 100X. Record your observations. Repeat the above procedure. Record your observations. Remove the slide from the stage, clean it and the cover slip, and put it away. Put the microscope on low power and put it away. 

Observations

Sketch a group of Elodea cells under each set of conditions. (Fresh water, distilled water, 5% salt solution, and 10% salt solution.) Label the sketches and note the cell structures/organelles 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.

Conclusions

Answer the following questions as completely as possible. 

1. What is the shape of the typical Elodea cell?

2. What are the small green blobs found inside the cells? What is their function?

3. What happens to the cells as the salt water flows under the cover slip?

4. What happens to the cells when the salt water is flushed out with distilled water?

5. Elodea normally lives in freshwater. What changes would you observe in the cells of an Elodea plant that was suddenly moved from freshwater to saltwater? Why?