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Comparing Plants and Animals
According to cell theory, all living organisms are made of cells. Cells are the basic unit of structure and function of all living things. In this activity you will explore the similarities and differences between plant and animal cells.

Onion Cell

1. Prepare a wet mount slide of a small piece of onion skin. Add 1-2 drops of methylene blue or Lugol's iodine to the slide, then apply a coverslip.
2. Observe the cells and identify at least 3-4 cell structures.
3. Take a photo of the onion cell with the motic cam. Measure an average cell with the motic cam. Add a title, 3 labels, and a descriptive caption.
_3.brubaker.onionskin.png
This is a picture of the skin of an onion. The cell membrane, cytoplasm, and nucleus are labeled.

4. Add concentrated salt solution to the slide and observe changes. Take another photo with the motic cam and label at least 3 parts to show changes.
Add a title and a descriptive caption to describe changes.
3.brubaker.concentratedonioncell.png
This is a picture of a concentrated onion cell. In this picture, you can see that the cell membrane is pulling away from the cell wall. The membrane shriveled up, and it still contains all of the organelles that would normally be in a plant cell.


Questions:
1. Describe the shape and arrangement of the onion cells.(2)
-The shape of the onion cell is kind of like a weird version of a rectangle with rounded edges. They are arranged closely together.
2. What happened to the cells when concentrated salt solution was added to the cells?(1) Why do you think this happened?(1)
- When the concentrated solution was added to the cells, they cell wall remained the same, but the membrane (and all of the organelles inside the membrane) shriveled up. I think this happened because The salt dehydrates the cell, causing the concentration to be higher.
3. What was the purpose of adding the methylene blue or Lugol's iodine to the slide?(1)
-The purpose of adding the methylene blue (Lugol's iodine) to the slide is so that you can see the individual cells better while observing them under the microscope.
4. What question do you have about this activity that has not yet been answered?(1) Do research to answer the question or design and perform an experiment to answer the question.(2) Remember to cite your sources.
Annamarie:
Q: After doing this activity, I have a question that I feel I must know. Does anything happen to the onion cell wall after the salt is added.
A: After researching that question, I have found that YES!, if you let the cell sit for at least 15 minutes, the cell wall actually swells because of the increased amount of water.
Resources:
[1]
[2]

Kali-
Why are onion cells so elongated? They are plant cells so the organelles you can see are the cell wall and the nucleus The cells are elongated and join together in a "brickwork" fashion.

[3]
[4]

Kali:
Q:
Why does the Elodea cell contain chloroplasts when the onion cell doesn't?
A:
Since the onion balb grows underground it doesn't get sunlight and so it doesn't have any chloroplasts or carry photosythesis.
[5]

Cheek Cell Lab

1. Obtain a flat toothpick and carefully scrape the inside of your cheeks. Add 1-2 drops of water to a slide, then add the cheek cells to the water by swirling the toothpick in the water. Add a drop of Lugol's iodine to the cell suspension. Carefully add a coverslip.
2. Observe the cells to identify 3-4 structures.
cheekbb.png
This is a picture of the cheek cell. The cell wall, cell membrane, and nucleus are labeled.

3. Take a photo of the cheek cell with the motic cam. Measure an average sized cell with the motic cam. Label at least 3 structures.
4. Finish by adding a title above your photo and a descriptive caption consisting of 1-2 sentences below the photo.

Assessment:

plant_and_animal_cells_checklist.png
plant_and_animal_cells_checklist.png

plant_and_animal_cells_checklist.png



Questions:
1. Describe the shape and arrangement of the cheek cells.(2)
-The cheek cells are very irregular and range from circles to rectangles.
2. Compare and contrast the cheek, onion, and elodea cells.(6)
- The cheek, onion, and elodea cells have their similarities and their differences. The onion and elodea cells are both arranged the same, very tightly packed together; whereas the cheek cells are randomly scattered. The onion cell is a nice, trim rectangle; but, the elodea is more rounded at the corners and the cheek cells are circular.
3. What question do you still have about this activity?(1) Do research to find the answer or design and perform an experiment to answer your question.(2)
Cite your research sources.
-Annamarie
Q: After doing this activty, I still have a question. Why do we stain the cells?
A: After researching this question I have found that cheek cells are stained because the internal organelles are transparent and difficult to see under the microscope.
[6]
[7]


Kali:
Q:
What is the importance of cheek cells?
A: Cheeks cells make up human cheeks, without them humans would not have cheeks.

Cell homework #3: How do the sizes of the onion, elodea and cheek cells compare to one another? Backup with research with other sizes of cells? How do all the activities make a common statement about cells, parts, size...?

Cell homework #4: Discuss how size is estimated using a microscope manually and digitally in your own words.
  1. ^ http://www.termpaperslab.com/term-papers/136703.html
  2. ^ http://answers.yahoo.com/question/index?qid=20081206141902AABdtXF
  3. ^ http://au.answers.yahoo.com/question/index?quid=20080703061911AARZ.gmj <ref>
    <ref> http://wiki.anwers.com/Q/How_many_cells_does_an_onion_skin_have_.html <ref>

    5. Explain what happens when salt water is added to an onion cell. You must use these words in your explanation: osmosis, diffusion, hypertonic, and hypotonic.
    -When salt is added to an onion cell, it becomes hypotonic, and the cell expands. Then, after we let the cell sit for a few minutes, it went through a process known as diffusion, or whenever molecules move from areas of high concentration to low concentration. The type of osmosis the cell went through is known as osmosis, or the movement of water from an area where there is a lot of water, to an area where there is little water. Then, the cell became hypertonic (meaning that the contents where the salt water is in the cell shrinks) and the membrane pulled away from the cell walls.



    Elodea Cell

    1. Prepare a wet mount slide of an elodea leaf. Remember to apply a cover slip. Move the slide around until you observe the elodea cells clearly. (Hint: Sometimes along the edge of the leaf the cells are more visible).
    2. Observe and identify 2-3 structures.
    3. Take a photo of an elodea cell with the motic cam. Measure an average cell with the motic cam. (Remember to measure the length, not the width).
    Add at least 2 labels to the elodea cell.
    4. Add concentrated salt solution to the slide and observe changes. Take another photo with the motic cam and label at least three structures to demonstrate changes that occurred.
    elodabb.png
    This is the picture of the elodea leaf cells. The cytoplasm, cell wall, and chloroplast are labeled.

    bbelodeasalt.png

    Questions:
    1. Compare and contrast the onion cell and the elodea cell.(2)
    - There are both differences and similarities between the onion cell and the elodea cell. Both the elodea cell and onion cell reacted the same way whenever the salt was added to them (the cell wall remained the same and the membrane and the organelles shrivelled up). A difference between the two cells is that the elodea cell contains microtubules, whereas the onion does not.
    2. Did the elodea and the onion cells react similarly to the addition of salt water? Explain.(2)
    -Yes, the elodea and onion cells reacted similarly whenever the salt water was added. You could still clearly see the cell walls, but the membrane's inside the walls pulled away, tightened, and shrivelled up. All of the organelles in the cell are still there though.
    3. What question do you still have about elodea or this lab activity?(1) Do research or design and perform an experiment to answer the question.(2)
    Cite your sources.
    Annamarie:
    Q: After conducting this activity, I still have a question. What happens to the cell wall whenever the cell membrane shrinks?
    A: After researching this question, I have found that the cell wall gets really, really salty and won't let any water into the cell.
    <ref>http://uk.answers.yahoo.com/question/index?qid=20090109033641AANCycp
  4. ^ curriculum.new-albany.k12.oh.us/alaughbaum/documents/CellTransport.ppt
  5. ^ http://faculty.kutztown.edu/friehauf/science_outreachflashcells.html
  6. ^ http://www.mos.org/sln/sem/staining.html
  7. ^ http://en.wikipedia.org/wiki/Staining