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Comparing Animal and Plant Cells Lab
Objectives
Examine the similarities and differences between the structure of cells in
animals and the structure of cells in plants.
Materials
• dropper bottles of iodine and methylene blue
• compound light microscope
• forceps
• elodea
• microscope slides and coverslips
• toothpicks
• prepared slides of three unknowns
Background
In this investigation, you will use a compound light microscope to
observe cells from animals and plants. First, you will make and view your own
slide of a leaf from Elodea, a pond weed and common aquarium plant. Then
you will make and view a slide of your own cheek cells.
Based on your observations of human cheek cells and Elodea leaf cells,
you will be asked to classify three slides of unknown cells as either animal or
plant cells.
Before you examine any cells, list the structural characteristics that
distinguish animal cells from plant cells.
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PART A: PLANT CELLS
1. Carefully tear off one small leaf near the top of an Elodea sprig. Using
forceps, place the whole leaf in a drop of water on a slide. Be sure it is flat
and not folded over. Place a coverslip on top of the leaf.
2. Observe the leaf under low power. The outermost part of the cell is the cell
wall. The many small, green organelles in the cells are chloroplasts.
3. Locate a cell that you can see clearly, and move the slide so that the cell is
in the center of the field of view. Examine this cell under high power.
4. Find an Elodea cell that is large enough to allow you to see the cell wall
and the chloroplasts clearly. Make a drawing of the entire field of view
including this cell in the space below. Label the cell wall and several
chloroplasts in your drawing.
5. The chloroplasts may be moving in some of the cells. If you observe no
movement, warm the slide in your hand or shine a bright lamp on it for a
minute or two. Then, reexamine the slide under high power, and look for the
movement of the cell’s contents. This movement is called cytoplasmic
streaming.
Because the cell membrane is pressed against the cell wall, you may not see
it. Also, the abundance of chloroplasts may hide other organelles in the cells.
You can make the cell membrane, vacuole, nucleus, and nucleolus more
visible by making a stained wet-mount slide of Elodea.
5.
Prepare a wet-mount slide of Elodea as you did in step 4, but substitute
iodine solution, a stain, for the water. Allow the iodine solution to diffuse
throughout the leaf.
6. Observe the stained cells under low and high power. Make a drawing of a
single stained Elodea cell under high power in the space below. Label the
central vacuole, nucleus, nucleolus, chloroplasts, cell wall, and cell membrane
if they are visible.
PART B: ANIMAL CELLS
1. Place a drop of water in the center of a clean glass slide.
2. Using the flat end of a toothpick, gently scrape the inside of your cheek.
The end of the toothpick will have several cheek cells stuck to it even
though you may see nothing but whitish gook.
3. Stir the water on the slide with the end of the toothpick to mix the cheek
cells with the water. Throw away the toothpick.
4. Put one drop of methylene blue stain on top of the drop of water
containing the cheek cells. Wait one minute, and then carefully place a
coverslip over the stained cheek cells.
5. You next must remove the excess stain from under the coverslip and
replace it with clear water in order to see the cheek cells. To do this, place
a paper towel at one edge of the coverslip. Then place a drop of water at
the edge of the coverslip on the opposite side. The stain under the
coverslip will be absorbed by the paper towel, and as the stain is removed
the clear water will be drawn under the coverslip.
Discard the paper
towel after it has absorbed the stain. See the diagram on the next page.
6. After the excess stain is removed, use the low power objective to locate a
few cheek cells under the microscope. Adjust the diaphragm to reduce the
light intensity and achieve greater clarity. You may need to move the slide
around to find intact cells.
7. Observe a few cheek cells under high power. Draw the entire field of view.
Identify and label the cell membrane, the cytoplasm, the
nuclear envelope, and the nucleus of one of the cells in your drawing.
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PART C: IDENTIFYING UNKNOWN CELLS
1. Obtain prepared slides of three unknown specimens.
2. Observe each specimen under low and high power. Record your
observations as described in the data table on the next page.
3. Clean up your materials, and wash your hands before leaving the lab.
Classification of Unknown Specimens
Unknown
Classification
(code
(plant or
number)
animal)
Analysis and Conclusions
Reasons for classification
1. What is the shape of an Elodea cell?
2. What is the general location of the nucleus in an Elodea cell?
3. What is the shape of the cheek cell?
4. What is the general location of the nucleus in a cheek cell?
5. Why are stains such as iodine and methylene blue used when observing
cells under the microscope?
6. According to your observations in this investigation, list several ways that
plant and animal cells are structurally similar and several ways that they are
different.
7. What do you think might be the function of cytoplasmic streaming in a
plant cell?
8.Which organelles that you read about in this chapter did you not see in this
investigation? Why do you think you were unable to see these organelles in
your slides?
9. In general, the surface of a tree has a harder “feel” than does the surface
of a dog. What cell characteristic of each organism can be used to explain
this difference?