Download Name

Name _________________________________________
Date _________________________
How Animal and Plant Cells Differ
Background
In this lab, we will be observing eukaryotic cells from plants and an animal (YOU!). Eukaryotic cells
are much more complicated than prokaryotic cells and will contain specialized structures called organelles, and
also possess a nucleus and nucleolus. Most cells are transparent so we will need to stain the organelles with
special stains (Iodine) so that we can see them under the microscope.
Although plant and animal cells have many structures in common, they also have basic differences.
Plant cells have a rigid cell wall, and possess chloroplasts with chlorophyll for photosynthesis. Animal cells
lack a cell wall and chloroplasts. Animal cells also lack a central vacuole common to plant cells which stores
water, enzymes and wastes.
You will first examine cheek cells (epithelial cells) from the inside lining of your cheek. Epithelium is a
type of tissue that lines the surfaces of many organs and cavities of the body. You will then examine cells from
a leaf of the freshwater plant, Elodea. The cells of this plant are green because they contain the pigment,
chlorophyll found inside the tiny circular chloroplasts for photosynthesis. You will also examine the thin inner
skin of the onion bulb. Since onions grow underground, there is no necessity for chloroplasts with chlorophyll.
They serve strictly to store food.
Purpose
 To observe eukaryotic cells and to observe their complexity.
 To observe both animal and plant cells and see how the structure and function of the cell structures
relate to their functions.
Prelab:
1. Since we are examining eukaryotic cells, what will we expect to see in them?
2. What will be added to the specimens to allow us to see the organelles in the cells?
3. What structures do we expect to find in a plant cell that are not found in an animal cell?
a. _________________________________
b. _________________________________
c. _________________________________
4. What is the function of each of the cells we will be examining?
a. Cheek cells. ___________________________________________________________________
b. Elodea cells. __________________________________________________________________
c. Onion cells. __________________________________________________________________
Materials
Microscope
Slides
Cover slips
Toothpick
Dropper bottle of water
Elodea
Onion
Potato
Forceps
Methylene blue
Iodine solution
Procedures:
Part I. Human Cheek Cells
1. To obtain cheek cells, gently rub the inside of your cheek with the flat side of a clean toothpick. Stir the
material from the toothpick in a drop of iodine on a clean slide.
2. Dispose properly of the toothpick NOW!
3. Carefully, place a cover slip on the slide and examine first under low power.
4. When you have found some individual yellow cells, center and move to medium and then high power
5. Draw 1 cell approximately 3 cm in the space below in pencil. Remember to indicate the power you are
on and label all structures to the right of your draw.
6. Label: Nucleus, nucleolus, cell membrane, and cytoplasm
_____x
Cheek Cells
Part II. Elodea Leaf Cells
1. Break off a small leaf near the tip of an Elodea plant (don’t be afraid of the water!). Using forceps, place
the entire leaf in a drop of iodine on a clean slide. Add a cover slip and observe first on low power.
What is the shape of the Elodea cells? _____________________________________________________
The boundary that you see around each cell is the cell wall. The numerous small, green bodies in the cells are
the chloroplasts.
2. Look for an area in the leaf where you can see the cells most clearly (remember these are 3D). Examine
these cells under high power, carefully focusing up and down with the fine adjustment to see all the
layers of cells.
Describe the shape and location of the chloroplasts. __________________________________________
___________________________________________________________________________________
____________________________________________________________________________________
_
____x
Stained Elodea
The cell membrane is pressed tightly against the inside of the cell wall (due to the central vacuole) and is
difficult to see. Furthermore, the numerous chloroplasts often make it difficult to observe other cell structures in
the Elodea leaf cells. In order to see the nucleus, nucleoli and vacuole more clearly, we needed to use the iodine
as a stain.
3. Draw 3 cells together (3 cm each) in the space provided above, with your drawing showing how they are
arranged and label the: Cell Wall, Cell membrane, Chloroplasts, Cytoplasm, and nucleus.
4. Color the chloroplasts green in your drawing. Be certain to make the cell wall look like a wall.
Part III. The Onion Cells
5. Remove the almost transparent layer of cells from the underside of an onion bulb scale. Place this layer
onto a slide. Make certain that the layer is flat and smooth. Add 2 – 3 drops of Iodine solution. Cover
with a cover slip. Wait a few minutes then observe and draw 3 cell under medium power. If you can go
up to high power, do so. Label the: Cell Wall, Cell membrane, nucleus, nucleoli, and cytoplasm
______X
Onion Cells
Conclusions and Applications
1.
What structures did all the observed cells have in common?
____________________________________________________________________________________
____________________________________________________________________________________
2.
What observed structures did either of the two plant cells have that the cheek cell didn’t?
____________________________________________________________________________________
____________________________________________________________________________________
3.
Some of the cheek cells are folded and wrinkled. What does this tell you about the thickness of the
cells?
____________________________________________________________________________________
____________________________________________________________________________________
4.
Explain why the elodea had chloroplasts while the onion cells did not.
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
5.
Place an X in the appropriate boxes to compare the 3 cell types of the structures found in each type of
cell.
Organelle
Cell
Membrane
Cell Wall
Cytoplasm
Nucleus
Chloroplasts
Cheek Cell
Elodea Cell
Onion Cell