Download Activity: Observing Onion Cells

Name _______________________________________________
Date ______________
Observing Onion Cells.2015
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Activity: Observing a Non-green Plant Cell (Onion Cells)
Goal: To observe, identify and describe the basic organelles of a non-green plant cell.
Background Information: All living things are made up of small units called cells. That is, cells
are the basic building blocks of living things just as atoms are the basic building blocks of
matter. Each cell contains living material surrounded by a border, or barrier that separates the
cell from its environment.
Some living things contain only a single cell. One-celled organisms are prokaryotes or
prokaryotic. Their genetic material is not surrounded by a membrane. Bacteria are prokaryotes.
Other organisms ranging from single-celled protists to multicellular plants and animals are
eukaryotes or eukaryotic. Their genetic material is membrane-bound. Nevertheless, every single
cell whether in a unicellular or multicellular organism can perform all the functions necessary for
life. Unicellular organisms may contain hundreds, thousands, or even trillions of cells.
Materials: onion slices, iodine stain, forceps, blank slides, coverslips, scissors, toothpicks
Procedure:
1. What I Know: Write two sentences about what you already know or think you know
about plant cells.
2. Place a drop of water on a slide.
3. Peel away a layer of onion slice and then peel off a very thin strip of onion membrane
from the inside of the layer.
4. Place the membrane on the water droplet on your slide. Try not to wrinkle the
membrane.
5. Add a drop of iodine to the slide and add a coverslip.
6. Observe your slide at 40X and then at 100X.
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7. What I Observed: Make two illustrations of what you observed one at 40 X and the
other at 100 X. In the higher power drawing, label the nucleus, the cell membrane, the
cell wall, and the cytoplasm. Use proper biological drawing techniques. Write one
caption describing your observations.
40X Onion Cells
100X Onion Cells
Caption: Write one caption describing your observations.
8. Questions: Answer the following in complete sentences.
a.
The cells of the onion are colorless, yet the onion is part of a green plant. Why
do you think the onion cells you observed are not green?
b.
Describe the structure and the function of the cell wall in plants.
9. What I Wonder: Pose a “why” or “how” question that you still may have concerning this
topic.
10. What I Learned:
CER (Claim, Evidence, Reasoning) Writing Prompts: Use the following prompts
to help you construct your lab conclusion, What I Learned.

Goal: State the goal of this lesson.
The goal of this lesson is…

Claim: What did you learn from the activity that satisfies the goal of this lesson?
This is an I Learned statement.
I learned that…

Evidence: How can you prove from your observations (data) that you learned
what you claim? This can be a general statement that you will explain in detail in
your explanation.
I know this because….

Explanation/Reasoning: Include the scientific principles that connect the
evidence and claim. (What’s the science that helps explain your claim and
evidence. The information can be from what you learned in our class
discussions, the textbook, or other resources that will help support your claim or
enhance your explanation.

Conclusion: Summarize the claim of the lesson (reword the claim) and include a
connection to self, text, or world.
Name ____________________________________Date __________________
Lab Activity: Observing Onion Cells
What I Learned: Write a summary of what you learned by completing this activity.
The summary should state a claim that is related to the goal of the lesson, provides
evidence from your observations, offers a scientific explanation (reasoning) that links
your claim to the evidence, and includes a conclusion.