Lab 2_ Microscopy Lab Exercises

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Mesa Community College *

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201

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Biology

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Apr 3, 2024

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Lab 2: Microscopy Lab Exercises Student Name: _________________ Lab Submission Remember to submit your work by uploading your completed exercises and answering the questions on the Submission assignment on Canvas. Microscope Labeling 1. Label the parts of the microscope shown below using the Microscopy Background page and video on Canvas. You are encouraged to write your answers, but can use the letters to create a key underneath the photo if you prefer to answer electronically. BIO201 @ MCC Lab 2: Microcopy, Page 1

Using the Microscope To complete this lab, watch the video linked on Canvas and answer the following questions as you watch the video. You may also need to refer to the background information on Canvas to answer some questions. Activity: The letter “e” - Dry mount ● Watch as the following steps are taken in the video: ○ Cut a small, asymmetrical letter, such as the letter “e”, out of the newspaper. Mount this letter upright on a slide. Place a cover slip over it to hold it in place. ○ Place the slide in the clamps of the mechanical stage and center the letter over the hole in the stage. ○ Bring the letter into focus under the scanning objective. You will notice the letter “e” is not only larger but its orientation is changed. Compare the orientation of the letter as seen through the microscope with its original appearance on the slide. ○ Turn the low power objective into place and focus. ○ Use the mechanical stage to move the letter around within the field of view. Note which knob controls which movement. You will use these controls a lot in the future so you might as well learn to "drive" them now. ○ Go to the high power objective. Do not forget to adjust the light and iris diaphragm. ● Answer the following questions. 2. How does the orientation of the letter “e” viewed through the microscope compare to its actual orientation on the slide? The orientation of the letter refers to whether it is right side up or upside down, and forwards or backwards. The letter is now flipped upside down and backwards after viewing through microscope. BIO201 @ MCC Lab 2: Microcopy, Page 2 A. Oculars B. Objective Lenses Nosepiece C. Oil Immersion Objective Lens D. Scanning Objective Lens E. Condenser Lens F. Stage G. Iris Diaphragm H. Lamp I. Base J. Mechanical Stage Adjustment Knobs K. Lens Assembly/ Body L. Arm M. High Power Objective Lens N. Low Power Objective Lens O. Mechanical Stage P. Coarse Focusing Knob Q. Focus Adjustment Knobs R. Power Switch

3. Is the orientation of the letter different at low and high power compared to scanning power? Low power lens has the same orientation as scanning power. High power will be too large to observe orientation through lens but will still be upside-down and backwards. 4. If the slide is moved to the right, which way does the letter appear to move in the field of view? Slide appears to move to the left. Activity: Threads - Dry mount ● Watch as the following steps are taken in the video: ○ Cut short pieces of red, blue, and green thread. Remove the letter from the slide used in the previous exercise. Use the same slide and cover slip again and again. ○ Carefully place the three threads on top of one another so they cross at a common point. Placing a cover slip over them will help hold them in order. ○ Examine the thread slide under the scanning objective and note the order in which they appear to be stacked. ○ Now observe the threads under the low and then the high power objectives. The purpose of looking at these threads at different magnifications is to develop an awareness of the restricted width of the field and shallower depth of focus at the higher magnifications. ● Answer the following questions. 5. List the color of threads in order from top to bottom as they were placed on the slide. Top: Blue Middle: Red Bottom: Green 6. Are the threads in the same order when viewed through the microscope? If they are in the same order, the top thread should appear to be closest to you and over the other threads. If they are in a different order, a different thread will appear closest to you or the order of the threads will change. Threads appear to be in the same color order as when observing with naked eye. Under lens, blue looks to be the top color, followed by red, then green. 7. Are all three threads in focus at once with the scanning objective? At scanning power, all three threads are still in focus. 8. Are all three threads in focus at once with the low power objective? At low power the green thread is in focus while blue and red are out of focus. BIO201 @ MCC Lab 2: Microcopy, Page 3

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9. Can you get a whole thread to be in sharp focus with the high power objective? In high power focus, none of the threads can be in complete focus. Calculation: Total Magnification Use the Microscopy Background page in Canvas to help you determine the total magnification. What is the total magnification when each objective is in place? 10. Scanning objective: 4X (10X) = 40X TOTAL 11. Low power objective: 10X (10X) = 100X TOTAL 12. High power objective: 40X (10X) = 400X TOTAL Converting Metric Units 13. Convert the metric units for the values contained in the following table. Use this table to help answer question #17 while paying special attention to the column headers in each table. Table 1. Microscope Specifications for the Leica Microscope. Objective Diameter of Field of View (mm) Diameter of Field of View (μm) Pointer Width (mm) Pointer Width (μm) Scanning 5.00 5000 0.150 150 Low Power 2.00 2000 0.060 60 High Power 0.5 500 0.015 15 Calculations: Metric Conversions Answer the following questions. Refer to the Metric Review Background page on Canvas if needed. 14. A red blood cell observed under oil immersion is estimated to be 8.5 µm in diameter. What is its diameter expressed in mm? (Always write in the units of measurement following the numerical value on your homework. Hint: copy paste to get the “µm” units.) .0085mm 15. What is a red blood cell’s diameter in nanometers (nm)? 8500nm 16. While looking at a slide you observe an unknown crystal lying next to a red blood cell. The crystal is about 2.5 times the diameter of the red blood cell. What is the size of the crystal in µm? 21.25 µm BIO201 @ MCC Lab 2: Microcopy, Page 4

Measurement with a Microscope Activity: Hair - Dry mount ● Watch as the following steps are taken in the video: ○ Place a hair on your slide and cover with your cover slip. ○ Locate and examine the hair under the scanning objective. ○ Turn the ocular and adjust the mechanical stage so that the pointer is on top of and running parallel to the hair. ○ Estimate the number of pointer widths that will fit over the top of the width of the hair. ○ The video explains how to estimate the diameter of the hair, so be sure to watch! 17. Use Table 1 (in question #13) above and your observations to fill in Table 2. Multiply the pointer width by the # of pointers parallel to the hair (or number of pointer widths you could fit across the hair width) to estimate the hair diameter. Table 2. Estimating the Diameter of a Hair. Pointer width (µm) x Number of pointer widths that would fit across the width of the hair = Hair diameter (µm) Scanning (150) x 1/3 = 45 Low Power (60) x 1 = 60 High Power (15) x 3 = 45 Microscope Care 18. Approximately how much do our microscopes cost? $2000 19. What should be used to clean the microscope lenses? Clean cotton swab or lens cleaner. 20. How should the microscope be put away at the end of the day? a. Turn it off. b. Wipe off all lenses. BIO201 @ MCC Lab 2: Microcopy, Page 5

c. After cleaning and letting lens dry, center the mechanical stage d. Put scanning objective in place. e. Don’t lower stage with the coarse focus knob. This will create new wear and tear. f. Place the dust cover over microscope. BIO201 @ MCC Lab 2: Microcopy, Page 6

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