Microscope Lab 3w6i72

Lab: Observing Cells Instructions: Follow the directions carefully for each part of the lab activity. Respond in complete sentences (where applicable) on a separate sheet of paper. Part A: Microscope Tutorial – Use the resources below to help you with questions 1-5. Resources  The video  http://www.borg.com/~lubehawk/mscope.htm  http://shs.westport.k12.ct.us/mjvl/biology/microscope/microscope.htm

QUESTIONS 1. Why do many biologists consider the microscope as one their most valuable tools? 2. Describe the ocular lens and the objective lens in your own words. 3. Why is the microscope we use in class considered a compound light microscope? 4. You are examining a cell on low power. You can see the cell membrane and nucleus. When you turn the microscope to high power, the cell becomes blurry and you can no longer identify any structures. What happened? 5. What type of microscope(s) do scientists use when they want to examine specimens that are smaller than those which can be seen using a light microscope? 6. Why are scientists unable to view living specimens with an electron microscope? 7. What is the difference between resolution and magnification? 8. Describe the function of these parts of the microscope in a complete sentence: a. Stage b. Stage clips c. Diaphragm d. Coarse adjustment e. Fine adjustment f. Arm g. Base 9. Describe the correct way to carry a microscope from one lab table to another. 10. You are absolutely positively NOT supposed to use the coarse adjustment once you have place the microscope on high power. Why? GET A STAMP! Part B: Microscope Quiz! – Now you may head to the lab. Please pair up with someone. No more than two people to a microscope, please! Materials Needed  Microscope  Microscope handout Procedure 1. Remove the plastic cover from the microscope. You don’t need to plug it in or turn it on just yet. 2. Examine the microscope handout. Locate each part on the microscope. Refer to the textbook or internet site above to confirm the function of each part.

3. You and your lab partner should quiz one another by pointing out the microscope parts and describing the function. 4. When you and your partner feel comfortable with this part, write the words, “Part B: Microscope Quiz” on your paper. Raise your hand and have your instructor come over to quiz you. GET A STAMP! Part C: Examining Prepared Slides – In this section, you will practice microscope techniques. Materials  Microscope  Prepared slides Procedure 1. Plug the microscope in to the closest outlet and turn on the microscope. 2. Turn the nosepiece to the scanning objective. (Hint: It’s the shortest objective. It has a red ring around it.) 3. Pick out a prepared slide that you’d like to view. 4. Place the slide onto the stage and secure it with the stage clips. 5. Using the coarse adjustment focus in on the specimen. 6. Once you have focused, turn the nosepiece to the low power objective. (This one has a yellow ring around it.) 7. Use the coarse adjustment to focus in on the specimen. 8. If you have too much light, turn the diaphragm to adjust the amount of light. You can tweek this to your liking. 9. Once you have focused with low power, turn the nosepiece to the high power objective. (Obviously the one with the blue ring around it.) 10. Use the fine adjustment to fine-tune your focus. DO NOT USE THE COARSE ADJUSTMENT! Notice how close the high power objective gets to the slide. 11. Before you remove the slide, turn the nosepiece back to the scanning objective. Now you can remove the slide. 12. You and your partner should practice this procedure on a few slides so that you get comfortable with focusing a specimen. It gets more difficult when your specimen is living! 13. Turn off your microscope, unplug it, and place the cover on it. Return to your desk and continue answering the questions below. QUESTIONS – Answer these questions on your lab sheet. 11. Why must you turn the nosepiece back to the scanning objective before you remove the slide? 12. You may have noticed that viewing the specimen on high power actually decreased the resolution even though it was more magnified. Why do you think this occurs?

Part D – Pre-lab for Creating Your Own Slides: Return to your seat. Read Part E then answer the questions below.

Questions (To be completed BEFORE you make your own slides.) 13. List the three parts of the Cell Theory in your own words. 14. Write a brief description of each of the following: a. Organelle b. Cell membrane c. Cell wall d. Nucleus e. Eukaryote 15. Describe the correct way to make your own slide for viewing your cheek cells. 16. List three things you will NOT do when using the microscope to view your cells. 17. Why is it necessary to use a stain in this lab exercise? 18. Which stain do you use for your cheek and skin cells? Plant cells? GET A STAMP! Part E – Creating your own slides - Cheek Cells: Read the procedure carefully. Procedure: 1. Before you begin, make sure your slide and coverslips are clean. You don’t want lint or fingerprints on your slide. If the slide is dirty, rinse it off and dry it well with a paper towel. 2. Put a drop of methylene blue on a clean slide. Caution: Methylene blue will stain clothes and skin. 3. Gently scrape the inside of your cheek with the flat side of a toothpick. Scrape lightly. 4. Stir the end of the toothpick into the stain and throw the toothpick away. 5. Place the coverslip at a 45-degree angle on the edge of the water/saliva mix. Allow the liquid to spread down the edge of the coverslip. Once it has spread, carefully lower the coverslip over the liquid. If you have a lot of air bubbles regardless of size, rinse of your slide and start over. It’s important that you make a good slide. 6. Use the SCANNING objective to focus. You probably will not see the cells at this power but you can eliminate blurriness by focusing now. 7. Switch to low power. Cells should be visible, but they will be small and look like irregular shaped objects similar to the cells below.

8. Once you think you have located a cell, switch to high power and refocus. (, DO NOT use the coarse adjustment knob at this point!)

9. Written work: Draw a picture of your cheek cell. Label the cell membrane, cytoplasm, and nucleus. 10. DO NOT RINSE OFF YOUR SLIDE UNTIL YOUR INSTRUCTOR HAS SEEN IT – YOU ARE RECEIVING CREDIT FOR YOUR LAB PRODUCT, TOO!

11. Write “Part E” on your paper. Turn your sign around and wait for your instructor to give you a stamp for completing this part of the lab. GET A STAMP Part F – Creating your own slides - Plant Cells: 1. Peel a translucent piece of tissue from the onion. The smaller the piece the better. (Translucent means that you can see light through the specimen, but it is not transparent.) 2. Place the piece of onion on a glass slide and add a drop or two of the iodine solution. 3. Cover the slide with a cover slip using the same technique that you used for your cheek cells. 4. Written work: Observe the onion cell under both low and high power. Draw a diagram of the onion cell. Label the cell wall, cell membrane, cytoplasm, and nucleus. 5. Write the words “Part F” on your paper. Turn your sign around and wait for your instructor to give you a stamp for completing this part of the lab. DO NOT RINSE OFF YOUR SLIDE UNTIL YOUR INSTRUCTOR HAS SEEN IT. Part G – Cleaning Up 1. Rinse off your slides and coverslips. Dry them with a paper towel and return them too the center of the lab table where they were found. 2. Make sure the stain and medicine droppers are at the center of the lab table next to the slides and coverslips. 3. Turn off the microscope, unplug it, and put the cover on it. GET A STAMP

Analysis and Conclusions Instructions: Read each question carefully. Respond to questions in complete sentences.

1. If you walked up to your lab table and a slide with a specimen similar to what you observed today was on the stage, how would you know that the specimen was a eukaryote?

2. The compound light microscope used in the lab is not powerful enough to view other organelles in the cheek cell.

a. Name three organelles that you DID see. b. Describe the function of the three organelles that you saw. c. Name and describe the function of 2 organelles that were NOT visible but you know were present in the cheek cells.

3. How were your cheeks cells similar to onion cells? How were they different? 4. What structures were present in the onion cells that were not present in your cheek cells? Describe the functions of these structures.

5. What other types of cells might have been observed on your cheek cell slide? Explain your answer.

6. What are the purposes of this activity? (Provide at least three.)

HONORS students answer questions 7 – 10.

7. How does using the stains in this lab demonstrate that the cell membrane is semi-permeable? 8. A cell’s shape often correlates with its function. How do you explain the shape of the onion cells versus your cheek cells?

9. An animal cell contains about 10 to 20 golgi apparatus whereas a plant cell contains several hundred. Why do you think there is such a difference in the number of these organelles in each cell?

10. Thinking ahead: Chromosomes are made up of DNA. Sections of DNA make up your genes. The nucleus of your cheek cell contains 46 chromosomes. The nuclei of your other body cells contain 46 chromosomes as well. How does your cheek cells know to be cheek cells when they contain the same chromosomes as your other body cells? (Tell me what you think.)