Download How Plant and Animal Cells Differ

Name __________________________________________
How Plant and Animal Cells Differ
Background:
Although plant and animal cells have many structures in common, they also have
basic differences. Plant cells have a rigid cell wall, and if they are green, they also
have chloroplasts. Animal cells lack both a cell wall and chloroplasts. They also lack
the central vacuole common to plant cells. Instead, animal cells will have many
smaller, specialized vacuoles.
You will observe and compare animal cells and plant cells. You will first examine
epithelial cells from the inside of your cheek. Epithelium is a type of tissue that
covers the surfaces of many organs and cavities of the body.
You will then examine cells from a leaf of the freshwater plant Elodea. Elodea is often
used in home fish tanks. The cells of this plant are green because they contain the
pigment, chlorophyll. Chlorophyll, which is found in chloroplasts within each cell,
enables plants to manufacture their own food.
Objectives of this activity:
1. Observe human epithelial cells (animal cells).
2. Observe Elodea cells (plant cells).
3. Describe the differences between animal cells and plant cells.
Materials:
Microscope
Dropper
Iodine Solution
slides
Eldoea forceps
Methylene Blue stain
coverslips
water
toothpick
CAUTION: Iodine and Methylene blue will stain your skin and clothes.
Procedure: Part I – Human Epithelial Cells
1. Place a small drop of water on a clean slide. Obtain epithelial cells by GENTLY
scraping the inside of your cheek with a clean toothpick. Stir the material
from the toothpick in the drop of water on the slide. Then immediately break
the toothpick in half and throw it away in the trash.
2. Add a small drop a methylene blue stain onto the slide. Carefully place the
coverslip on the slide. (Listen to the teacher for tips on how to decrease the
amount of fluid under the coverslip.) Examine the slide under low power.
When you find some cells that are separate from each other, switch to high
power and examine them.
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3. Make a drawing of two or three cells as they appear under high power in the
circle below. Label the nucleus, nuclear membrane, cytoplasm, and plasma
membrane of one of the cells.
4. What is the shape of the cells? (square, circular, oval, or
irregular)
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5. Describe the appearance (color/texture) of the cytoplasm.
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6. Clean off your slide carefully. Do not get any stain on you.
Cheek cells
Part II – Elodea Leaf Cells
1. Break off a small leaf near the top of an Elodea plant. With the forceps place
the entire leaf in a drop of water on a slide. Add the cover slip to the slide.
2. Examine the leaf under low power. What is the shape of the leaf’s cell?
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3. The boundary that you see around each individual cell is the cell wall. The
numerous small, green dots in the cells are the chloroplasts.
4. Look for an area in the leaf where you can see the cells most clearly. Examine
the cells under high power, carefully focusing up and down with the fine
adjustment. Notice that you are moving through different layers of the leaf.
5. Describe the shape and location, in the cell, of the chloroplasts.
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6. As you examine the cells, you may see the chloroplasts moving around. You
will need to look closely and watch for a few moments to notice the
movement. If they are not moving, warm up the slide in you hand or over a
light for a few minutes. Do not allow the slide to dry out.
7. Describe how the chloroplasts move in a cell. Describe the speed at which
they move and the direction they move, etc.
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Name __________________________________________
8. Make a drawing of an Elodea cell, as you see it under high
power, in the circle to the left. Label the cell wall, chloroplasts,
and any other structures you can see.
9. The cell membrane is pressed tightly against the inside of the
cell wall and is difficult to see. Furthermore, the numerous
chloroplasts often make it difficult to observe cell structures in
the leaf’s cell. In order to see the nucleus, nucleoli, and vacuole
more clearly, you are going to use a stain.
Elodea cells
10. Clean off your slide. Break off another Elodea leaf and place it in a drop of
Iodine Solution on your slide. Add the cover slip and wait a minute or two for
the Iodine stain to penetrate into the cells. Then examine the stained cells
under low power and then high power.
11. Make a drawing of a stained cell in high power in the circle below. Label the
cell wall, cell membrane (if visible), chloroplasts, nucleus, nucleolus, and the
large vacuole.
12. What structures can you see more clearly after
staining the Elodea leaf cells with the Iodine?
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Elodea cells stained with Iodine
13. Are the chloroplasts still moving around in the cell with the
iodine stain added to the leaf?
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Name __________________________________________
Lab Analysis and Conclusion Questions:
1. What cell structures do human epithelial (cheek) cells have in common with
Elodea cells? Please list 3 structures. (3 pts)
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2. How do human epithelial (check) cells and Elodea cells differ? (2 pts)
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3. Some of the epithelial cells are folded or wrinkled up. What does this tell you
about the thickness of the epithelial cells? (1 point)
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4. Chloroplasts cannot move by their own power. Something has to move them
around the cell. How do you think they move around the cell? What cell part
may be responsible for moving them? (2 pts)
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5. What did the iodine solution do to the activity of the cell? (1 point)
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