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.
Onion Cell:
stephaarononioncell.png
This is a picture of the onion cell. It shows the nucelus, cell membrane, and cell wall.


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.

Onion Cell With Salt Water
stefaaroncellsalt.png
This is a picture of the onion cell after the salt solution was added. It shows the water, cell wall, and cell membrane. The cell membrane is pulling away from the cell wall, and shriveling up.


Questions:
1. Describe the shape and arrangement of the onion cells.(2)
They are long, tubular shaped. They are arranged very closely and tightly 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 salt solution was added, the cell membrane began to pull away from the cell wall. The inside organelles also began to shrink and shrivel up. I think this happened because the salt was dehydrating the cell. It was taking the water out of the vacuoles.

3. What was the purpose of adding the methylene blue or Lugol's iodine to the slide?(1)
The purpose of adding the iodine was so you could see the cell better.

  • 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.
Does the onion cell have chloroplast? The onion cell does not have chloroplast in it because because the cell is from the bulb and the bulb is underground so it does not go through photosynthesis and that is what chloroplast is used for.
[1]

  • 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.
Diffusion forces the salt water through the permiable cell wall, this is called osmosis. The salt water is a hypertonic solution that in turn
shrinks the cell membrane because the vacuole is filled with hypotonic solution and it is drawn from the cell membrane.

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.
Elodea Cell:
Cells_Elodea_cell_labeled_pic.png
This is a picture of the elodea cells without saltwater but the cell we labeled is already shrunk a little bit.

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.
Elodea Cell With Saltwater:
Cells_Elodea_cell_saltwater_labeled_pic.png
This is a picture of the elodea cells with saltwater added and as you can see the cell membranes have shrunk up more.

Questions:
  • 1. Compare and contrast the onion cell and the elodea cell.(2)
Both of the cells are plant cells and are rectangular. The elodea cells have chloroplast in them and the onion cells do not. The onion cell does not go through photosythesis and the elodea does. They both have the basic parts of plant cells, including cell membranes and walls.

2. Did the elodea and the onion cells react similarly to the addition of salt water? Explain.(2) Yes, the elodea and the onion cell acted the same. The cell membrane pulled away from the cell wall and shriveled up.

  • 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.
Why does the salt water dehydrate the cell? Salt attracts water, which causes it to absorb the water. It basically absorbs all fluids, causing the cell, or the person (if you drink the salt water), to dehydrate . When you add saltwater to the cell, the cell membrane pulls away from the wall and shrinks, this is called plasmolysis.
[2]
[3]
[4]

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.
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.
Cheek Cell:
Cells_Cheek_cell_labeled_pic.png
This is a picture of the cheek cells that we studied, they are not perfect circles.

4. Finish by adding a title above your photo and a descriptive caption consisting of 1-2 sentences below the photo.


Questions:
1. Describe the shape and arrangement of the cheek cells.(2)
They are uneven and wavy circular shaped, they are found scattered and sometimes stuck together.
2. Compare and contrast the cheek, onion, and elodea cells.(6)
The onion and elodea cells are rectangular and arranged neatly, the cheek cells are circular and are not arranged in any certain way. We found a nucleus in all of the cells and a cell membrane. We were able to drop salt water on the onion and elodea cells to separate the cell wall and cell membrane but in the cheek cells we couldn't do that because they don't have a cell wall. Also, the elodea cels were the only ones containing chloroplasts. The cheek cells did not have them because they are animals, and the onion cell did not have them because they do not grow underground. .
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)
How do cheek cells move if they don't move on their own? The cheek cells don't move on their own but they have two organelles that function for cell movement, these are the Gogli Apparatus and Cytoskeleton.
[5]

Cite your research sources ||
  1. ^ http://wiki.answers.com/Q/Why_don%27t_onion_cells_have_chloroplasts
  2. ^ http://wiki.answers.com/Q/Why_does_salt_water_dehydrate_you
  3. ^ http://answers.yahoo.com/question/index?qid=20080922155912AA4VDt7
  4. ^ http://www.madsci.org/posts/archives/2002-12/1040175859.Bt.r.html
  5. ^ http://wiki.answers.com/Q/Cheek_cells_do_not_move_on_their_own_what_two_organelles_function_for_cell_movement