Download Lab 5H - Comparing Plant and Animal Cells PDF

Cell Structure and Function
Lab #5H: Comparing Plant and Animal Cells
Pre lab Discussion:
Ever since the first microscope was used, biologists have been interested in studying the
cellular organization of all living things. After hundreds of years of observations by many biologists,
the cell theory was developed. The cell theory states that the cell is the structural and functional unit of
living things. Cells contain structures called organelles that carry out life processes. Cells can be
classified by the types of organelles they contain. In plant and animal cells, similarities and differences
exist because of varied life functions.
In this investigation, you will compare the structures of a typical plan cell (Elodea) and a
typical animal cell (human).
Problem:
Formulate a hypothesis to answer the questions: How are plant and animal cells alike? How are they
different?
Materials:
Dissecting needle
Medicine dropper
Elodea leaf
Microscope slide
Microscope
Prepared slide of human skin cells
Safety
Put on a laboratory apron if one is available. Put on safety goggles. Always handle the microscope
with extreme care. You are responsible for its proper care and use. Use caution when handling
microscope slides as they can break easily and cut you. Be careful when handling sharp instruments.
Procedure:
Part A. Examining Plant Cells
1. Take a microscope from the storage are and place it about 10 centimeters from the edge of the
laboratory table.
2. Carefully clean the eyepiece and objective lenses with lens paper.
3. Place a drop of water in the center of a clean microscope slide as shown in figure 1.
Figure 1
4. Remove a leaf from the Elodea plant and place it on the drop of water on the slide. Make sure
that the lead if flat. If it is folded, straighten it with the dissecting needle.
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Cell Structure and Function
5. Carefully place a cover slip over the drop of water and Elodea leaf as shown in figure 2.
Figure 2.
6. Place the slide on the stage of the microscope with the leaf directly over the opening in the
stage.
7. Using the low-power objective lens, locate the leaf under the microscope. Turn the coarse
adjustment knob until the leaf comes into focus.
8. Switch to medium-power objective lens, focus, and then switch to the high-power objective
lens. CAUTION: when turning to the high power objective lens, you should always look at the
objective from the side of your microscope so that the objective lens does not hit or damage the
slide.
9. Observe the cells of the Elodea leaf. Draw and label what you see in the appropriate place in
Observations. Record the magnification of the microscope.
10. Carefully clean and dry your slide and cover slip.
Part B. Examining Animal Cells.
1. Place a prepared slide of human cells on the stage of the microscope with the center of the slide
directly over the opening in the stage.
2. Using the low power objective lens locate a few cells under the microscope. Note: you will
need to reduce the amount of light coming through the slide in order to see the cells more
clearly. Adjust the diaphragm as necessary.
3. Switch to medium-power objective lens, focus, and then switch to the high-power objective
lens. CAUTION: when turning to the high power objective lens, you should always look at the
objective from the side of your microscope so that the objective lens does not hit or damage the
slide.
4. Observe some cells. Sketch and label what you see in the appropriate place in observations.
Record the magnification of the microscope.
5. Return your microscope to the storage area.
Observations
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Cell Structure and Function
Magnification _______
Elodea Cells
(Plant cells)
Magnification _______
Human Skin Cells
(Animal cells)
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 a human skin cell?
4. What is the general location of the nucleus in a human skin cell?
Analyze and Conclude
1. How are plant and animal cells similar in structure?
2. How are plant and animal cells different in structure?
Thinking skills and applications
1. What is an advantage of using a wet-mount preparation instead of a dry-mount preparation in
the study of living cells?
2. Explain why you could not use an oak leaf in this investigation.
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Cell Structure and Function
3. In general, the surface of a tree has a harder feel than does the surface of a dog. What cell
characteristics of each organism can be used to explain this difference?
4. If you were given a slide containing living cells of an unknown organism, how would you
identify the cells as either plant or animal?
More to Explore
1. Remove the skin from fruits and vegetables such as tomatoes, onions, and leeks. Prepare wet-mount
slides for each skin and observe the cells under the low-power and high-power objectives of your
microscope. Sketch and label what you see. What cell structures do these cells have in common? How
do these cells compare with animal cells?
2. Make a wet-mount slide of an Elodea leaf using 10% salt solution (10g of table salt dissolved in
100mL of water) instead of water. Examine the leaf under low-power and high-power. Describe any
differences in characteristics between these Elodea cells and the cells observed in water.
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