Download cell-lab-cheek-onion-elodea-08-09

Name________________________________
Date _____________________
Examination of Cells under the Microscope
I. Examination of Human Cheek Cells:
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Using a clean toothpick, gently scrape the inside of your food-free cheek once or
twice.
Rub the (now invisible) cells over a small area (smaller than a cover slip) near the
center of your slide.
Add one drop of Iodine stain.
Cover with a cover slip.
Find an isolated cheek cell under low power.
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Position your slide so that this cell is in the center of your field of view. Focus clearly.
Change the objective lens to medium power. Repeat the above procedure.
Change the objective lens to high power. Focus clearly.
Draw this cheek cell as it appears in your microscope.
Label the nucleus, cytoplasm, and cell membrane.
Cheek cell (high power)
II. Examination of Onion Cells:
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Obtain as thin an onion section as possible by pulling back one “skin” layer from a
small piece of onion.
After peeling this thin section, lay it on the slide without folds, to the best of your
ability. Forceps may be needed to transfer this onion layer to your slide without
wrinkling.
Add one or two drops of Iodine stain on top of your onion section.
Find a collection of cells under low power.
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Focus these onion cells clearly.
Change the objective lens to medium power. Repeat the above procedure.
Change the objective lens to high power. Focus clearly.
Draw these onion cells as they appear in your microscope.
Label the nucleus, cytoplasm, and cell wall in one onion cell.
Onion cells (high power)
Name________________________________
Date _____________________
III. Examination of Elodea Cells:
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Place one Elodea leaf flat on the center of your slide.
If needed, add one drop of water to prevent the leaf from drying out due to heat
from the microscope lamp.
Find a collection of Elodea cells under low power.
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Focus these cells clearly.
Change the objective lens to medium power. Repeat the above procedure.
Change the objective lens to high power. Focus clearly.
Draw these Elodea cells as they appear in your microscope.
Label the chloroplasts and the cell wall.
If time permits, add one drop of Iodine stain to your Elodea sample.
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Observe the cells as directed above.
Is the cell nucleus now visible in any cells? If so, draw this organelle in your
illustration below.
Elodea cells (high power)
Analysis Questions:
1. How are onion and Elodea cells similar?
2. If both onion and Elodea are plants, why don’t onion cells contain chloroplasts?
3. How is the cheek cell different from the plant cells that we examined?
4. Why do all cells contain a nucleus?