Name: ___________________________
Block: ________
Date: __________
Bio A – Cell Comparison Lab (50 points)
Introduction:
Ever since the first compound microscope was invented and used in the late 1500s, biologists have been
interested in studying the cellular organization of living things. After hundreds of years of research, the cell
theory was developed, which in part stated that the cell is the structural and functional unit of living things. All
cells contain the same basic structures, including a cell membrane, cytoplasm and DNA; however, only
eukaryotic cells contain nucleus and other structures termed “organelles” to carry out cell functions. These
types of cells can be classified further by the structures that they have into plant and animal cells, which have
some similarities and difference due to their varied life functions. For example, plants contain thick cell walls
and chloroplasts that are green and make food for the plant
You will investigate the structures of 2 typical plant cells, the onion and Elodea plant, 1 animal cell, a
human cheek cell, and 1 bacterial cell to compare and contrast them.
Objective: To use the microscope to correctly compare, contrast, identify and explain similarities and
differences between eukaryotic and prokaryotic cells.
Materials:
Microscope
Methylene blue
Toothpicks
Slides & Coverslips
Yogurt
Pipette
Water
Onion
Colored pencils
Iodine
Elodea (Anacharis)
Procedure:
REMEMBER: Turn on your microscope and make sure that it is in low power. Clean the microscope
using lens paper if it is dirty and difficult to see. Keep the diaphragm entirely open and change it if
needed as you view the slides. Make sure that the stage is in the lowest position before starting.
ALWAYS focus the slide under the lowest power first
Human Cheek Cell
1. Use a toothpick to gently scrape some cells from the internal lining of your mouth (cheek). You will
need to scrape for about 30 seconds to get enough cells.
2. Smear the toothpick on your slide to spread out the cells and saliva.
3. Add 1 drop of methylene blue to your slide. Discard the toothpick after. Place a coverslip on it on
an angle to complete the wet mount.
4. Observe, draw, and label the basic structures of the cheek cells.
Onion
1. Carefully peel off the thin inner layer of the onion section and place it on the slide. Add 1 drop of
iodine to the onion.
2. Use a toothpick to smooth it out if needed. Then place the coverslip on the slide on an angle to avoid
air bubbles.
3. Observe, draw, and label the basic structures of the onion cells.
Elodea
1. Tear off 1 young leaf from the plant.
2. Make a wet mount by only using 1 drop of water (no stain needed). Cover it with a coverslip.
3. Observe, draw, and label the basic structures of the Elodea cells.
Yogurt Bacteria
1. Place a tiny dab of yogurt on a slide. Make a wet mount by adding 1 drop of water and placing a
coverslip on it on an angle.
2. Observe, draw, and label the basic structures of the bacterial cells.
For all 4 examples, use the circles given to:
- Draw the cell(s) to scale (0.5 points per)
- Give it a title (example: “Onion Cell, Low Power”) (0.5 points per)
- Provide a total magnification (0.5 points per)
- Label all visible parts in pencil (1 point per)
- Color each diagram using colored pencils (0.5 points per)
1.
Title:
Title:
Lowest Magnification:
Highest Magnification:
2.
3.
4.
Title:
Title:
Lowest Magnification:
Highest Magnification:
Title:
Title:
Lowest Magnification:
Highest Magnification:
Title:
Title:
Lowest Magnification:
Highest Magnification:
Data Table 1: List the cell parts that were visible for each cell type (1 point per box)
Cell Type
Structures Observed
Human Cheek Cells
Onion Cells
Elodea (Anacharis)
Cells
Yogurt Bacteria
Directions: Answer the following analysis questions in complete sentences.
1. Why are stains such as methylene blue and iodine used when observing cells under a microscope? (1 point)
Why were they not used for the Elodea leaf? (1 point)
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2. How does the structure (shape) of your cheek cells compare to that of the onion cells? (1 point) Explain why
they are differently shaped (i.e. which structure(s) is/are responsible for this?). (1 point)
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3. If you were given a slide containing living cells of an unknown organism, how would you identify the cells
as either plant or animal cells? (2 points)
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4. Describe the shape and size of the yogurt bacteria. How do they differ from the other organisms viewed?
(2 points)
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5. The mouth is the first site of chemical digestion in a human. Your saliva starts the process of breaking down
the food that you eat. Keeping this in mind, what organelle do you think would be numerous inside the cells of
your mouth? (1 point) Explain why. (Hint: this organelle was not seen in this lab.) (1 point)
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6.
A. What structures (name 2) are found within the cells of eukaryotes that are NOT found within
prokaryotes? (1 point) Of the cells observed which are classified as prokaryotes, and which are classified
as eukaryotes? (2 points).
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B. What other structures (name 4) might you find in prokaryotes and eukaryotes that you didn’t observe
in this lab? (2 points) Why would you not see them in the lab? (1 point)
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7. How is the structure and organization of prokaryotic cells different from eukaryotic cells? How are they
similar? Using the Venn diagram note at least 3 differences (3 pieces of information for each circle), 2
similarities in the 2 circle overlaps (any of them), and 1 similarity between all three (in the center) about how
these 3 cell types are both similar and different. (6 points)
Plant Cells
Animal Cells
Prokaryotic Cells