Download Onion and cheek Cell Lab

Science Lab Sek-Catalunya
Onion and cheek Cell Lab
1rst ESO
Onion & Cheek Cell Lab
1. Background Information:
One of the first scientists to look at cells under a microscope was an English scientist by the
name of Robert Hooke. He viewed and described the appearance of cork under the
microscope and decided to name the tiny box-like structures that he observed “cells”
because they looked like the small chambers where monks lived.
By the early part of the 19th century, it was accepted that all living things are composed of
cells. Cells come in a variety of shapes and sizes, and cells perform different functions.
Although cells may appear outwardly different, they resemble each other because they
share common structures. In this lab you will look at two types of cells, a human cheek cell
and an onion cell and see how they are similar and how they are different.
2. Purpose: In this lab, you will prepare and observe cells from both a plant (onion)
and an animal (your own cheek!!).
3. Materials: You will need the following materials: glass slide, coverslip, cotton
swab, methylene blue, iodine stain, onion tissue, and your own cheek cells.
Science Lab Sek-Catalunya
Onion and cheek Cell Lab
1rst ESO
4. Assignment: Your assignment is to prepare and observe as many samplings of
both types of cells as possible and sketch them in the spaces provided on this sheet.
You are also required, on your sketch, to label any visible parts or organelles, as
well as list what magnification you used. Lastly, you need to write down any other
interesting observations (difference between cells, cool things you saw, etc.) on this
sheet.
5. Procedure:

For the onion cell:
a. Get a glass slide and place a small amount of onion tissue in a side.
b. Add a small drop of iodine stain directly to the tissue. Careful, iodine is not toxic,
but it will stain both your skin and your clothes.
c. Place a coverslip over the newly stained tissue.
d. Place the slide on the stage and view the slide under the low power. Once you have
found an area with several good cells, switch to medium power and then to high
power. Remember to only use the fine adjustment to focus at higher powers.
e. Go through the three powers, focusing each time, making sketches, and writing
down observations. Be sure to write what magnification you used for each sketch.
f. Be sure to label any parts you see. You may be able to see: cell wall, nucleus, and
cytoplasm.
Science Lab Sek-Catalunya
Onion and cheek Cell Lab
1rst ESO
6. Results:
Magnification:
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Observations:
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Magnification:
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Observations:
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Magnification:
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Observations:
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Science Lab Sek-Catalunya
Onion and cheek Cell Lab
1rst ESO

For the cheek cell:
a. Add a drop of methylene blue in the other side of the slide.
b. Using the cotton swap, gently scrape the inside of your cheek.
c. Swirl the cotton swap, now with cheek cells, in the methylene blue drop on the
slide.
d. Place a coverslip on the stained cheek cells.
e. Put the slide on the microscope, making sure the microscope is on LOW
POWER!
f. Go through the three powers, focusing each time, making sketches, and writing
down observations. Be sure to write what magnification you used for each
sketch.
g. Be sure to label any parts you see. You may be able to see: cell membrane,
nucleus, and cytoplasm.
Don’t forget to clean up!!
Science Lab Sek-Catalunya
Onion and cheek Cell Lab
1rst ESO
7. Results:
Magnification:
___________________________
___________________________
Observations:
___________________________
___________________________
___________________________
___________________________
___________________________
Magnification:
___________________________
___________________________
Observations:
___________________________
___________________________
___________________________
___________________________
___________________________
Magnification:
___________________________
___________________________
Observations:
___________________________
___________________________
___________________________
___________________________
___________________________
Science Lab Sek-Catalunya
Onion and cheek Cell Lab
1rst ESO
8. Discussion Questions:
Answer the following questions in complete sentences
1.
2.
3.
4.
How does the shape of the onion cells differ from that of the cheek cells?
Which cells seem to be arranged in a more regular pattern?
What structures were you able to see in both types of cells?
Both plant cells and animal cells contain mitochondrion and yet there were not
visible in the cells you viewed in this lab. Does this mean that these organelles
are not found in cheek and onion cells? Why or why not? Explain your reasoning.
5. In class and in your reading you learned that one difference between plant and
animal cells is that plant cells contain chloroplasts. Were any chloroplasts visible
in the onion cells? Why or why not? Explain your reasoning.