Download Cells: The Basic Unit of Life

Cells: The Basic Unit of Life
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Background information: When different types of cells are viewed under a microscope, different cell parts
can be seen. Certain living cells are best for showing parts like a nucleus or plasma (cell) membrane.
Cells from producer organisms (plants) will show parts such as chloroplasts and cell walls. Most consumer
organisms (animals, fungi, etc.) have cells that do not have these parts, although fungi have cell walls. We
will not consider fungi in this investigation.
An amoeba is an excellent way to view a simple animal cell. Amoebas are large single celled organisms in
which you can view the nucleus, cell membrane, cytoplasm, and pseudopods (“false-feet”) which are
extensions of the cytoplasm that amoebas use to move.
Human cheek cells may be used for viewing the plasma membrane and cytoplasm. A cell membrane is a
thin outer boundary which surrounds the cell and separates it from neighboring cells. Cytoplasm is the inner
portion of the cell that supports the smaller cell parts.
Onion cells may be used to show a cell’s nucleus and nucleolus. These two structures appear within most
living cells. There may be several nucleoli appearing as tiny dots within each cell’s nucleus. The nucleus
will appear as a round structure inside each cell.
Another cell part found in the cells of many producers is the green chloroplast. Common water plants such
as Elodea show these structures well.
Purpose: In this investigation, you will:
 observe a variety of living and once-living materials under the microscope.
 determine if these materials do or do not show a cellular type of organization
 study and locate under the microscope six specific cell parts
 compare the cell parts found in plant and animal cells
Procedure:
A. Cork Cells
1. Obtain a slide of the amoeba from the front of the room
2. Put the prepared slide on the microscope and focus. Start and low power and zoom into one
specimen under high power.
3. Examine the amoeba under high power
4. Draw the amoeba and label the cell membrane, nucleus, cytoplasm, and pseudopods
5. Label the total magnification.
B. Cheek Cells
1. Place a drop of methylene blue stain and a strand of hair onto a slide. The hair will help you
locate the layer with the cheek cells. CAUTION: METHYLENE BLUE WILL STAIN
CLOTHING.
2. Gently scrape the inside of your cheek with the rounded end of a toothpick. You will not be able
to see anything on the toothpick.
3. Dip the toothpick into the stain on the slide and mix.
4. Add a coverslip and examine under low and high power.
5. Locate and examine cells that are separated rather than those in clumps.
6. Draw a cheek cell under high magnification. Label the plasma membrane and cytoplasm. Label
the total magnification.
C. Onion Cells
1. Cut a small section of an onion scale. Peel off a thin layer of onion tissue.
2. Place onion layer onto slide. Make sure the layer is perfectly flat.
3. Stain the onion with iodine. CAUTION: IODINE STAINS CLOTHING AND SKIN.
4. Place a coverslip on the onion.
5. Observe the cells under both low and high power. Note the brick wall appearance of the cells,
with cell walls separating the cells.
6. Locate a small round structure, the nucleus, within each cell. Examine carefully by focusing up
and down through the cell. The nucleus is surrounded by the nuclear membrane.
7. With high power, observe the tiny dots within the nucleus. These are the nucleoli (plural of
nucleolus).
8. Draw a single onion cell as it appears under high power.
9. Label the cell wall, nucleus, nucleolus, and nuclear membrane. Label the total magnification.
D. Plant Cells
1. Prepare a wet mount of the leaf of a water plant.
2. Use low power to position the leaf so you are looking near the edge. Locate green, oblong cells.
Examine them on high power.
3. Note the small, green structures inside each cell. These are chloroplasts. Attempt to find
chloroplasts that appear to be moving.
4. Draw a single plant cell on high power.
5. Label the cell wall and chloroplasts. Label the total magnification.
Cell Lab
Name_____________________________
Purpose: In this investigation, you will:
 observe a variety of living and once-living materials under the microscope.
 determine if these materials do or do not show a cellular type of organization
 study and locate under the microscope six specific cell parts
 compare the cell parts found in plant and animal cells
Procedure: See handout.
Observations:
See drawings ______________________________________________.
Analysis:
A. Cork Cells
1. Is the amoeba you used alive? __________________________________________________
2. What is the large dark circle you can see under high power called? ______________________
3. Do these units appear filled or empty? ____________________________________________
4. What is in this structure? _________________________________
5. What are the large extensions of the cytoplasm called? _______________________________
6. What are they used for? ___________________________________________
7. Is an amoeba a plant or animal cell?
8. How can you tell? ___________________________________
B. Cheek Cells
1. Describe the shape of a cheek cell. _________________________________________________
2. Are cheek cells produced by plants or animals? _______________________________________
3. How do you know? _____________________________________________________________
4. Are cheek cells alive? ___________________________________________________________
5. Where is the plasma membrane? __________________________________________________
6. Where is the cytoplasm? _________________________________________________________
7. What does the cytoplasm look like? ________________________________________________
8. Why was stain put on the cheek cells? ______________________________________________
C. Onion Cells
1. What is the shape of an onion cell? ________________________________________________
2. Are onion cells produced by plants or animals? ______________________________________
3. Do onion cells have cell walls? ___________________________________________________
4. What shape is the nucleus of an onion cell? __________________________________________
5. Where is the nucleus located? _____________________________________________________
6. What is the shape of the nucleolus? ________________________________________________
7. What structure separates the contents of the nucleus from the cytoplasm? ___________________
8. Why were the cells stained? ______________________________________________________
D. Plant Cells
1. What is the shape of the plant cell? ________________________________________________
2. Is there a cell wall present? ______________________________________________________
3. What color are the chloroplasts? __________________________________________________
4. What shape are the chloroplasts? __________________________________________________
5. What cell part are chloroplasts in? _________________________________________________
6. Are chloroplasts present in animal cells? _______ Explain. ____________________________
Summary Chart:
Nucleus
Cell Wall
Cytoplasm
Nuclear
Membrane
Nucleolus
Chloroplasts
Cell
Membrane
Animal Cell
Plant Cell
Conclusion:
The parts that are found in both animal and plant cells are __________________________________
______________________________________________________________________________________.
The parts found only in animal cells are _____________________________________________________.
The parts found only in plant cells are ______________________________________________________.
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