The objective of this lab was to learn what a microscope reveals about plant and animal cells. The completion of this lab should teach the participant the differences between plant and animal cells and how to examine samples of the covering tissues of a plant (the onion) and of an animal (the participant) using the epidermis and cells from a cheek swab of epithelial tissue.
1. Packet Pages L14 to L16
2. Onion Chunks
3. Compound Microscope
4. Microscope Slides
5. Covers Slips
8. Lugol’s Iodine Solution
9. Tweezers (optional)
10. Paper Towels
11. Flat Toothpicks
Part A: Cells of the Onion Epidermis
1. Gently peel off one of the thin layers of the inside of the onion chunk.
2. Spread out while placing the skin (membrane) flat in the center of the slide.
3. Use the pipette to add a drop of water to the slide before putting the cover slip on top in a fashion that disallows air bubbles.
4. Begin the examination under low power and adjust the slide until you find an area fit to observe (cells outline are defined).
5. Switch to high power and examine individual cells.
6. Revert to low power and remove the slide. Stain the cells with Lugol’s iodine at the edge of the cover slip.
7. Draw the stain through by placing a small piece of paper towel to the opposite edge of the cover slip.
8. Replace the slide while focusing under low power.
9. After locating a viewable cell switch to high power and focus with fine adjustment.
10. Adjust the diaphragm as needed.
11. Slowly focus up and down to observe the cells.
12. Record your observations according to the directions on L-15.
Part B: Cells from your Cheek Epithelium
1. Place a small drop of Lugol’s iodine solution on a clean slide.
2. Use the wide end of the toothpick to gently scrape the inside of your cheek.
3. Spread the matter on the toothpick in the stain on your slide, and then discard the toothpick in a waste container.
4. Focus under low power and move your slide to find an area with a few yellowish separate cells.
5. Switch to high power and study the cells while adjusting the gradually fine adjustment up and down.
6. Record your observations on page L-15.
Analysis and Conclusion
1. All living things are composed of cells.
2. Similar cells are organized into groups called tissues.
3. Plant cells are surrounded by cell