Download Plant and Animal Cells

Plant and Animal Cells
Name____________________Class______Date____________
Introduction: Cells are the smallest unit of living organisms. Cells from plants and animals have
similarities in their structures, but also important differences related to their functions. In this
investigation, onionskin cells and human cheek epithelial cells will be stained and observed using the
microscope.
Materials: microscope, two glass slides, iodine stain, methylene blue stain, two cover slips, piece of
onion, cotton swap, paper towels, vinyl gloves
Procedure: Read each set of instructions carefully before beginning the exercise.
PART A: Observing Plant Cells (Onion Skin Wet Mount)
1. Be sure to put on a lab apron and vinyl gloves before handling the materials. Peel the delicate
transparent tissue from the inner surface of a piece of onion using forceps (tweezers).
2. Make a wet mount by placing the tissue, unwrinkled, in a small drop of water on a glass slide.
3. Add one small drop of iodine stain to the tissue and cover with a cover slip as directed. (* be careful the iodine can stain and burn the skin!)
4. Examine the onion cells at low power, focus as necessary.
5. Next examine the cells at medium and high power.
6. Prepare a diagram of onion skin tissue showing three to four cells as they appear under high power.
Label the structures you can identify from the microscope. (examples - cell membrane, nucleus, etc.)
Remember to follow guidelines for drawing and labeling a proper biological diagram. An example is
shown below.
Answer the following questions:
1. Describe the shape of the cells. _________________________________________________________
2. What cell structures and organelles can you see?
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3. Onions are plants, but no chloroplasts are observed on the slide.
Why?_________________________________________________________________________________
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PART B: Animal Cells (Human Cheek Cell Wet Mount)
1. Place a drop of water on a clean slide. Gently scrape the inside of your cheek with the cotton swab,
rubbing it along the inside surface of the cheek. Stir the material on the swab in the drop of water on the
slide. (Properly dispose of the cotton swab.)
2. Add one small drop of methylene blue stain to the slide and then add a coverslip as directed. Place the
edge of the paper towel next to the border of the coverslip to absorb excess stain.
3. Focus and examine the slide under low power before moving to the higher magnifications.
4. Prepare a diagram showing 3 - 4 cells of the cheek as seen under high power and label structures you
can identify. (Don't forget to identify magnification of the drawing.) An example of what the cells look
like under high power is shown below.
Answer the following questions.
4. What are the shapes of the cells? ______________________________________________________
5. What cell structures can you identify?____________________________________________________
6. Would the cells normally be attached to one another? Explain.
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7. Some of the cells may be folded or wrinkled. What does this indicate to you about the thickness of the
cells?
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8. Describe how the cheek cells differ in their appearance when compared to the plant cells.
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