Lab. Elodea, Onion, and Cheek Cell Lab. Be your best. Cell Biologist s Name: Period: Date: Mrs. Bouchard -7 th Grade Science

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1 Purpose Ques*on: How do plant cells and animal cells differ? Cheek Cell Lab Materials: Water bo6le with dropper toothpick glass slide coverslip lens paper methylene blue safety goggles lab apron paper towel Cheek Cell Wet Mount Procedure: Be your best. Cell Biologist s Name: Period: Date: Mrs. Bouchard -7 th Grade Science Elodea, Onion, and Cheek Cell Lab 1. Clean and dry a glass slide. Using a dropper, add one drop of water to the center of the slide. 2. Using the flat end of a toothpick, gently scrape the inside of your cheek. 3. Being careful not to smear the water droplet, sgr the water on the slide with the end of the toothpick to mix the cheek cells with the water. See Figure 1 below. Then, throw away the toothpick. Lab Figure 1

2 2 4. Put one drop of methylene blue stain directly on top of the drop of water containing the cheek cells. 5. Wait one minute, then carefully place a cover slip over the stained cheek cells. 6. To remove the stain from under the cover slip and replace it with clear water, place a piece of paper towel at the edge of one side of the cover slip. 7. Then, place a drop of water at the edge of the cover slip on the other side. See Figure 2 below. The stained water under the cover slip will be absorbed by the paper towel. As the stain is removed, the clear water next to the cover slip on the opposite end will be drawn under the cover slip. drop of water piece of paper towel Figure 2 8. Place the slide on the stage of the microscope with the center of the cover slip directly over the opening of the stage. 9. Using the low power objecgve lens, locate a few cheek cells under the microscope. Switch to medium power and draw what you see. Do not forget to include the details of the image! 10. Switch to the high power objecgve lens. Observe some cheek cells. Sketch what you see (include details). Label the nucleus, the cell membrane, and cytoplasm on one of the cells you see. 11. Rinse the slide and cover slip. Dry both carefully.

3 3 Medium Power x High Power x Direc*ons: Answer all quesgon with complete sentences (except quesgon 4). 1. Describe the shape of the cheek cells. 2. What job does the drop of water seem to do? _ 3. Why was methylene blue stain used? 4. Was this cell a plant or an animal cell? 5. Explain what evidence you observed in the cell that helped you answer quesgon 4. _

4 4 Onion Cell Lab Materials: onion skin iodine bo6le with dropper glass slide cover slip Onion Cell Lab Procedure: 1. Get an onion secgon. 2. From the bo6om side of the onion secgon, peel off a li6le piece of the thin skin. It should be about 1cm x 1cm. 3. Place this skin in the middle of a clean microscope slide. 4. Add one drop of iodine to the skin. 5. Cover the droplet with a cover slip, let the cover slip fall onto the droplet. 6. Put the slide on the stage and view the specimen under low power. Draw what you see including details. 7. Turn the objecgve to medium power and draw what you see including details. 8. Focus the cells on high power and draw their details. Label the nucleus, cell wall, cytoplasm, and vacuole(s) on one of the cells. Rinse and dry the cover slip and slide when finished. Low Power x Medium Power x

5 5 High Power x Answer the quesgons using compete sentences. 1. Describe the shape of the onion cells. _ 2. Is an onion cell a plant cell or animal cell? Explain your answer using evidence form the lab. 3. Why was the iodine used in this lab?

6 6 Elodea Cell Materials: water bo6le with dropper forceps Elodea leaf glass slide cover slip paper towel Elodea Cell Procedure: 1. Put a drop of water in the center of a clean slide. 2. With the forceps, remove a leaf from the Elodea plant and place it on the slide. Make sure that the leaf is flat. If it is folded, straighten it with the forceps. 3. Carefully place a cover slip over the drop of water and the Elodea leaf. 4. Place the slide on the stage of the microscope with the leaf directly over the opening on the stage. 5. Using the low power objecgve lens, locate the leaf under the microscope. Draw what you see, including details. 6. Turn the objecgve lens to medium power. Draw what you see including details. 7. Turn the objecgve lens to high power. Observe the cells and draw what you see including details. Label the cell wall, cytoplasm, nucleus, and one chloroplast on one of the cells you see. 8. Carefully clean and dry your slide and cover slip. Low Power x Medium Power x

7 7 High Power x Answer the quesgons using compete sentences. 1. Describe the shape of the Elodea cells. _ 2. Is an Elodea cell a plant cell or animal cell? Explain your answer using evidence form the lab. 3. Why are most plants green?

8 8 Conclusion: Use evidence from the lab to answer the purpose quesgon on page 1 (C.E.R. format).