But First, Let me take a Cell-Fie
Onion Cells
Step 1
Prepare a wet mount slide of onion cells using directions supplied by your
teacher.
Step 2
Focus on the cells with low power. Then, observe them under medium power
and high power.
Step 3
(a) Make a drawing of six adjoining cells (cells touching each other) as they
appear under high power on your own paper. Record ALL THE DETAILS you can
see with high power. For one of the cells in your drawing label these parts: cell
wall, cell membrane, cytoplasm, and nucleus. Use your rules for making an
ACCURATE scientific drawing.
(b) The cell membrane always surrounds the cytoplasm. Usually it is so close to
the cell wall that you cannot see a separation between them, but draw the cell
membrane on your diagram, just inside the cell wall. Use pages 39-44 your
textbook to help you identify the cell parts.
Human Cheek Cell
Step 1
Take a clean toothpick and gently scrape the inside of your mouth.
Step 2
Smear the toothpick on the center of the microscope slide for 2 to 3 seconds by
rolling and rubbing the toothpick along the slide. Make a wet mount by adding
a drop of methylene blue solution and placing a coverslip on top. Methylene
blue stains negatively charged molecules in the cell, including DNA and RNA.
This dye is toxic when ingested and it causes irritation when in contact with the
skin and eyes. Remove any excess solution by allowing a paper towel to touch
one side of the coverslip.
Step 3
Focus on the cells with low power, Then, observe them under medium power
and high power. If you have trouble finding the cells, examine the prepared
slide of human cheek cells using the low, medium, and high power objectives.
The cells seen are squamous epithelial cells from the outer epithelial layer of the
mouth. The small blue dots are bacteria from our teeth and mouth.
Step 4
(a) Make a drawing of three cells which appear near each other on the slide on
your own paper. Include ALL THE DETAILS you can see under high power.
(b) Again, use pages 39-44 of your textbook to help you identify the cell parts.
Remember, your microscope does not allow you to see all the parts shown in
the diagram on page 41. For one of the cells in your drawing label these parts:
cell membrane, cytoplasm, and nucleus.
Name ___________________________
Block _________
Date ___________________
But First, Let me take a Cell-Fie
Onion Skin Stained with Iodine, ________
Human Cheek Smear Stained with Methylene Blue, ________
Analysis
1. Refer back to your models (drawings) to complete the chart below. Put a  in the column for
the type of cell in which you observed the organelles which are listed.
Cell Organelles
Onion Cells
Cheek Cells
2. What are some key ways that the plant cells (onion) and animal cells (cheek) you observed
are similar? What are some key ways that the plant cells and animal cells you observed are
different? Use a Venn diagram to display your findings.
Application
1. Eukaryotic cells have a nucleus whereas prokaryotic cells do not. Are the plant cells and the
animal cells you observed prokaryotic cells or eukaryotic cells? Provide evidence to support
your answer.
2. Consider the diagram of the cell on the right. Using what you have
learned about plant and animal cells, decide whether the diagram
represents a plant cell or an animal cell. Provide evidence to
support your decision.