What is Life? Project PART 1: Looking at Cells Lab

Transcription

1 What is Life? Project PART 1: Looking at Cells Lab Directions: Complete the drawings and answer the questions in the space provided. For each drawing: Title the drawing of the specimen (e.g. Cork Cells) Create a circular field of view by tracing a Petri dish. For each specimen, DO NOT fill the whole circle with cells. Just draw a few cells (4-6) for each specimen. These cells must be clear drawings. Take your time and draw what you see. Cartoons and diagrams of cells will not receive full credit. All drawings must be the size that you see them in the field of view. DO NOT draw them larger or smaller than they appear in the microscope. The magnification used while drawing the cell (e.g. 400x) Appropriately labeled structures from the following list: Cell membrane/cell wall chloroplast nucleus cytoplasm Chromoplast amyloplast vacuole You may add any other scientific observations next to your drawings You will begin by observing cork cells under the microscope. CORK CELLS: (one drawing) 1. With the single edged razor blade shave a very thin slice from a piece of cork, the thinner the better. Remember light must pass through your slice in order for you to see it under the microscope. CAUTION: Cutting edges can cause serious injuries. Always cut away from yourself and others. Immediately return the razor blade when you are done with it. 2. Prepare a wet mount slide of the cork slice. On the clean slide, place a drop of water and your cork specimen. Lay the cover slip on at a 45 degree angle to avoid trapping air bubbles. 3. View under low power. View closely. Draw your specimen below: 4. Finish the following prompt: The cork cells appear to be empty in the middle. I would expect this because.

2 PROKARYOTIC CELLS: Lactobacillus from yogurt culture (one drawing) 1. These specimens will be set up for you ahead of time. They will be magnified at 1000 times, don t touch the course adjustment knob. 2. Draw your specimen below 3. Describe what you see the lactobacillus cells doing. Describe their movement. EUKARYOTIC PLANT CELLS ONION CELLS: (Two drawings) 1. Put a drop of water on the center of a clean dry slide. 2. Get a small slice of onion from the supply area. You must use the shiny layer of tissue that is on the outside of the onion slice. Hold your slice of onion with its concave (inward curve) side away from you. You will be using the tissue that is on the side of the onion that is now facing you. With your thumbs and fingers, snap the piece of onion as demonstrated by Ms. Wade. Use your knife/scissors to cut off a small piece, about the size of a pencil eraser.

3 3. Using your scissors and forceps transfer the small piece of onion tissue to the drop of water on your slide. Make sure that the membrane is flat and not folded. Spread out with forceps if necessary. Add the cover slip and avoid trapping air bubbles. 4. Examine your onion tissue under low power. Remember to keep your light level low. 5. Draw your unstained specimen. 6. Answer the following prompt: By looking at the onion under the microscope I can tell that this is a plant cell because 7. Remove the slide from the microscope stage. 8. Add iodine stain to the cells using the following technique: a. Place one drop of iodine at the edge of the cover slip. b. Hold a small piece of paper towel on the edge of the other side of the cover slip. The stain will be pulled under the cover slip and into the specimen. 9. Examine the stained onion cells under low and high power. Draw the stained onion cells on high power.

4 10. Answer the following prompt: Under the microscope the stained onion cells appear different than the unstained onion cells ELODEA CELLS: (one drawing) Elodea is a common pondweed often used to study photosynthesis and plant cell structure. 1. Remove a young leaf from the tip of a sprig of Elodea 2. Prepare a wet mount slide with a cover slip. You will need 2 or 3 drops of water. 3. Observe the Elodea cells on low and medium power. You may not be able to see them at high power because the thickness of the leaves. 4. Look for the chloroplasts. They are the green bodies that are suspended in the cytoplasm. The chloroplasts might be moving along with the cytoplasm. Let Ms. Wade know if you do not see them moving. This is called cytoplasmic streaming. 5. Focus up and down through the leaf. As you slowly move the focal plane through the leaf, count the number of cell layers that come into clear focus. 6. Draw and label the elodea cells. Plastids are cellular organelles of certain Eukaryotes where food or pigments are made and stored. Chloroplasts are a type of plastid in which pigment chlorophyll is stored. For the following cells you will examine two other types of plastids: amyloplasts and chromoplasts. POTATO CELL: (one drawing) 1. Using a razor blade cut a section of potato as thin as possible. CAUTION: Cutting edges can cause serious injuries. Always cut away from yourself and others. Immediately return the razor blade when you are done with it. 2. Place a thin section of potato on the slide.

5 3. Add several drops of water and place on the cover slip. 4. Examine under low. Center the thinnest part of your potato section in the field of view. 5. Examine under medium and high power and select one that gives you the best view of your potato cells. 6. Stain the potato slice with iodine stain using the technique described above. 7. Return the slide to the stage and view it under medium or high power. 8. Draw the stained potato cell. Each intensely stained structure is called an amyloplast. Label your drawing. RED BELL PEPPER CELLS: (one drawing) 1. Using a razor blade cut a small section of red pepper. CAUTION: Cutting edges can cause serious injuries. Always cut away from yourself and others. Immediately return the razor blade when you are done with it. 2. Remove the outer skin layer and place the section on a wet mount slide with a cover slip. You will need a piece about the diameter of a pencil. 3. Examine under low and high power. 4. Draw and label the bell pepper under high power.

6 5. Answer the following prompt: Compare and contrast the red bell pepper cells to the other plant cells that you have observed. EUKARYOTIC ANIMAL CELLS CHEEK CELLS (two drawings) 1. The cells that line the inside of your cheek are called epithelial cells. They are constantly being sloughed off like the cells of the outer skin. As a result, some of these cells can be easily and painlessly removed. 2. Put a drop of water on a clean dry slide. 3. To collect some epithelial cheek cells gently scrape the inside of one of your cheeks with the flat end of the toothpick using an up and down motion. 4. Transfer your cheek cells from the end of the toothpick by swirling the end of the drop of water on the slide. Do not spread the water drop around on the slide. Swirl times. 5. Add a cover slip and view under low and high power. The cells will look like small transparent baggies. The cells tend to clump together so try to locate one by itself for clear viewing. Note their shape. 6. Draw the unstained cheek cell on high power.

7 7. Remove the slide from the stage for staining. Place a drop of iodine stain at one edge of the cover slip. Draw the stain under the cover slip with a piece of paper towel at the opposite edge like you did earlier. 8. Draw the stained cheek cell under high power. 9. Answer the following prompts: was visible in the stained cheek cells; this was not visible in the unstained cheek cells. The animal cells differed from the plant cells

8 Complete the chart that compares the different cells that you have viewed. Cell Type cell wall cell membrane Cork Lactobaccillis Onion Elodea Potato Red Pepper Cheek chloroplast or chromoplast or amyloplast nucleus eukaryotic or prokaryotic