Science 7-Yellow House Mrs. Shapiro
Name ______Date _____ Group _____
Laboratory Investigation:
What do Elodea cells look like under the microscope?
Background:
All life is made up of different types of cells, each performing a specific purpose. Muscle cells are obviously different from fat cells, and both are different from nerve cells. Yet these cells which seem so different from each other are in fact, very similar. Cells are the basic units of structure and purpose in living things. These statements are part of the Cell Theory.
If you look at a sample of living material under a microscope, you will see the individual cells. In most cells the nucleus is very easy to pick out. The nucleus is the control center, organizing all the activities that occur within the cell. In eukaryotic organisms, the nucleus is surrounded by a ______. Surrounding the nucleus there may be small dots or blobs; these are organelles. Each organelle performs a specific job for the cell. Two examples of these organelles, the chloroplasts (plants only), which make food from sunlight and the mitochondria, which digest food and provide energy for the cell.
There are some differences between plant and animal cells. In this lab investigation we will observe plant cells from Elodea, a freshwater plant.
Materials:
Microscopes, Glass Slides, Cover slips, Elodea, Paper towels and Lugol’s Iodine solution
Procedure:
1. Examine a sprig of Elodea. With your forceps take a young leaf near its growing tip. Place it on a slide, add a drop of water and apply a cover slip. Observe the leaf under low power.
2. Observe the arrangement of cells in the leaf you are examining and draw your section of the leaf AS IT APPEARS under low power.
3. Switch to high power; do not touch the coarse adjustment knob. Carefully focus using the fine adjustment knob and draw a high power view of several elodea cells. Label the cell parts. You should see: cell wall, cytoplasm, nucleus and chloroplasts.
4. Look for moving chloroplasts close to the cell wall. This movement is the result of cyclosis, the streaming movement of the cytoplasm of the cell.
5. Stain your Elodea leaf with Lugol’s solution on the microscope stage in the following way: Place a drop of Lugol’s at one edge of the cover slip; holding a small strip of paper towel against the opposite edge of the cover slip will draw the Lugol’s solution under the cover slip. Observe whether nuclei have become visible.
6. Clean up your lab area by rinsing off the glass slides and cover slips and wiping off the table.
Observations and Data:
Don’t forget to label all organelles that are visible.
1) Predict how an Elodea leaf would respond to light.
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2) What is cyclosis (aka cytoplasmic streaming) and why do you think that this might be important to the cell? Explain.
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3) What cell structures are made visible by staining with iodine?
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