Considering the microscope parts, briefly describe when you would use (what the purpose is) for each of the parts below; (50 pts each; total 200 pts) Simple stain defined: We can see/observe: We can see/observe: We can see/observe:
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Chapter 4 - What are the differences between light and electron microscopes (what are used, magnification, resolution)? What sort of images do we see with VS? Why is your scope in the lab called a compound light microscope? What are the four main types of images produced by light microscopy? What are the basic parts of a light microscope, and what are their functions? Why do we use oil for the oil immersion lens (what purpose does it serve)? What is a simple stain vs. differential stain? What can simple staining tell you about your bacterial sample? What are the steps for a Gram stain, and what does each do specifically? Don't forget that making a heat-fixed smear is the first step. What are the two genera (plural for genus) that are acid-fast positive, and why? How do you perform an acid-fast stain, and what will you observe? Name two genera that produce endospores. How do you perform an endospore stain, and what will you observe? What type of stain is used to stain for a capsule in bacteria? What is an example of a biochemical test? What is a dichotomous key, and what is it used for?
Adi S.
19. If you move the microscope ruler to the right, how do you see the image move? a. to the right b. to the left c. toward you d. away from you e. none of the above 20. A microscope is parfocalized if when going from the low power objective to the high power objective all you need to adjust for focus is the fine adjustment knob. a. true b. false 21. The focal length (working distance) a. is the distance between the objective lens and the object when the objective is in focus b. Goes down as the magnification of the objective lens goes up c. a and b only d. a, b and c are correct 22. Refraction is the bending of light as it passes from a lens into the air. a. true b. false 23. Dyes are a. molecules that absorb part of the visible spectrum b. have a chromophore (colored part) and an auxochrome (attaches the dye to the substrate) c. often are positively charged, whereas the bacterial cell is negatively charged d. all the above e. none of the above 24. A simple stain a. uses one dye b. allows the viewer to see morphology (size, shape and structure) and arrangement of microbes. c. permits the differentiation of two groups of microbes d. a and b only e. a, b and c 25. The gram stain may give variable results because a. In an aging culture the cell wall begins to disintegrate and gram-positive cells may not fully retain the crystal violet-iodine complex b. Smears of bacterial colonies or organisms may be decolorized too long c. Some antimicrobial agents may change bacterial cell walls d. a and b e. a, b and c
BIO2073: Microbiology Lab Smears and Simple Stains: Individual Assignment 1. List 3 bacterial characteristics that can be determined using a simple stain. (1 pt) 2. Explain how a basic stain allows us to visualize our microbes. Be sure to address the chemistry of the reaction. (You may want to refer to your lab text for a refresher on how basic stains work.) (2 pts) 3. Explain how a negative stain differs from a basic stain. (1 pt) 4. Explain how you would heat fix a slide. (1 pt) 5. List two effects of heat-fixing a slide. (1 pt) 6. List 3 commonly used basic stains. (1 pt) 7. List 2 commonly used negative stains. (1 pt) 8. What would happen if you did not leave the stain on your sample long enough? (1 pt) 9. What would happen if you did not heat-fix your sample prior to staining? (1 pt) Bonus! Why might a negative stain, which does not heat fix the bacterial sample, be a better choice for viewing some microbes? (1 pt)
Josee P.
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