Cell Lab Make a wet mount of onion cells by adding IODINE instead of water. Plant cells: Elodea and Onion Make a wet mount of a single elodea leaf. Make your way to 40x. Look for the same cell parts. Q: What do you immediately notice (see) that makes this “object” different than the objects you viewed in the microscope lab? See if you can find a nucleus (holds the genetic material (DNA)) in some cells. (Every onion cell has a nucleus, but they don’t always absorb the iodine stain so they may be difficult to see.) Notice that the leaf is made of two layers of transparent cells. Focus on the layer of large cells. See if you can locate the following structures (Check those that you see.): _____ Cell Wall: Thick outer covering of each cell. _____ Chloroplasts: Green disks. They turn light into sugar through a process called photosynthesis. _____ Cytoplasm: The clear fluid in each cell. _____ Cell Membrane: Pressed against the cell wall, so it is NOT visible. Remember that it is there. _____ Vacuole: Water-filled sac found in the middle. If you can’t see it directly, see if you can observe it indirectly by noting the chloroplasts sitting around its edge. Notice that the cytoplasm may appear “grainy” in some areas. Vacuoles are the “clear” areas of the cell, and they take up most of the center of the cell. The membrane surrounding the vacuole may be difficult to see. Again, the cell membrane is pushed up against the cell wall and will NOT be visible. Don’t forget that it IS there. Make a drawing of 3 onion cells that take up most of the circle. Label the parts that you could see. Now observe cells near the vein of the leaf. Q: Can you spot any chloroplasts that are moving? If yes, describe how they are moving. If you’ve really searched and couldn’t find any, just say so. Using your colored pencils, draw one elodea cell so that your drawing stretches across the circle. Label only the parts that you found. Q: Chloroplasts have no way of moving on their own. Hypothesize: Why are they moving? Q: Hypothesize: Remembering where onions come from, why don’t onions have chloroplasts? Animal Cells: Human Cheek Cells and Amoeba Gently scrape the inside of your cheek with a toothpick, and smear the toothpick on a clean slide. Add one drop of iodine. After scanning on 4x and 10x, look at a few cheek cells under 40x. Notice the following: _____ NO cell wall. _____ Cell Membrane: the soft outer covering of animal cells; controls what enters and leaves the cell _____ Nucleus _____ Cytoplasm (clear) Draw and label two cheek cells so they stretch across the circle. QUESTIONS: 1. Why were you not able to see a nucleus in some cells? 2. What is the difference in function between cells that have chloroplasts and those that do not? 3. Which organelle usually present in plant cells is absent in the stained onion skin tissue? 4. Which cell part is common to both the onion skin cells and the elodea leaf cells? 5. In what ways do animal cells resemble plant cells? 6. In what ways do animal cells differ from plant cells? a.) Watch an Amoeba projected on the classroom screen. An Amoeba has a changing structure called a pseudopod (“false foot”) that helps it move and capture prey. Watch a pseudopod changing. Draw and label one amoeba. (Cell membrane, cytoplasm, nucleus, vacuole, pseudopod) b.) c.) 7. Draw and label a generalized plant cell in one circle and an animal cell in the other.