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Lab: Comparing Plant and Animal Cells Problem: What cell structures can be seen with a light microscope? Materials: Flat toothpick Microscope Slides Cover slips Medicine droppersElodea plant Scalpel Onion Forceps Methylene blue stain All of this must be copied into your lab journal! Procedures: Human epithelial (cheek) cells 1. Using a medicine dropper place a drop of methylene blue on a slide. Gently scrape the inside lining of your cheek with the flat edge of a toothpick. Mix the material on the toothpick in the drop of stain. Immediately dispose of the toothpick in the trash. CAUTION: Do not reuse toothpicks. Add a coverslip to the slide. 2. View under low power, moving the slide to center a single cell in the field. Change to high power and observe the cell carefully. 3. Record your observations in the data table. Sketch the cells and label the structures inside. Onion cells 4. Using a medicine dropper place a drop of methylene blue on a slide. Carefully peel a very thin layer of onion skin from the onion and place a small piece of the onion skin on the slide. Add a coverslip. 5. Focus on low power first and then on high power. Repeat step 3. Data and Observations: Cell Type Sketch and Magnification Name and Number of Structures Other Observations Human Cheek Cells Onion Cells Questions and Conclusions: 1. What structures did you observe in the onion but not in the human cells? What are their functions? 2. Methylene blue is a common type of stain. What was the function of this stain? Why are stains necessary in cell observation? 3. Compare the shape of the onion cells to the shape of the cheek cells. What accounts for the difference? 4. What structures were visible in all the cell types? 5. What differences were seen between the plant and animal cells?