Plant and Animal Cells
PART A: Plant Cells ( Onion Skin Wet Mount)
1. 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 Lugol's iodine stain to the tissue and cover with a cover slip as directed. (* be careful - the Lugol's 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. 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.
Answer the following questions:
1. Describe the shape of the cells. ___________________________________________
2. What cell structures and organelles can you see? ______________________________
3. How come there are no chloroplasts evident? ________________________________
PART B: Animal Cells ( Human Cheek Cell Wet Mount)
** Care must be taken when doing this part of the lab to handle and dispose of the cells with appropriate concern. Using a prepared epithelial cell slide would also work.
1. Place a drop of water on a clean slide. Gently scrape the inside of your cheek with the blunt end of a clean toothpick and stir the material on the toothpick in the drop of water on the slide. (properly dispose the toothpick)
2. Add one small drop of methylene blue stain to the slide and then add a coverslip as directed.
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 and label structures you can identify. (Don't forget to identify magnification of the drawing.)
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. ____________________
7. Some of the cells may be folded or wrinkled. What does this indicate to you about the thickness of the cells? ___________________________________________________
8. Explain how these cells differ from the plant cells viewed previously._______________
Image of a human epithelial (cheek) cell as seen through a compound microscope. Magnification - 400x.