PORTAGE LEARNING BIOD 171 MODULE 3 EXAM MODULE 3

  Portage Learning BIOD 171 Module 3 Exam Module 3 1. A micrometer is defined as A. 10-3 B. 10-6 C.10-9 D. 10-12 B. A micrometer is one-millionth of a meter. 2. True or False: A nanometer is longer than a micrometer. False. A nanometer is 1,000 times smaller than a micrometer. 3. Resolution and contrast are two critical factors that influence your ability to see an object. Explain each. Resolution refers to the distance between two objects at which the objects still can be seen as separate. Poor or low resolution means two (or more) objects may appear as one. Contrast is the difference in light absorbance between two objects. Poor contrast gives a high background and makes the visualization of multiple objects difficult. For instance, trying to identify 2 dark colored objects at night (low light = low contrast) versus the same 2 objects in the middle of a sunny afternoon (bright light against 2 dark objects = high contrast). 4. Assuming a constant (non-adjustable) light source power, identify the part of the microscope you would adjust to limit the amount of light entering the microscope. Select all that apply. A. Objective B. Condenser C. Iris diaphragm D. Eye piece C. The iris controls the amount of light that passes through the sample and into the objective lens. Thus, it can be adjusted (opened or closed) to alter the amount of light. 5. What is the total magnification (relative to your eye) of a sample imaged with a 60x objective and a 10x eyepiece? Show your math. 60 x 10 = 600x magnification 6. True or False: A cell that is adherent, flat (thin) and unstained is easily identified using bright field microscopy. False. Adherent, flat cells are almost invisible due to the limits on both resolution and contrast. 7. Which of the following could be seen clearly by the unaided eye? Select all that apply. A. Bacteria with diameter of 24 μm B. Protozoa with diameter of 150 μm C. Virus with a diameter of 0.2 μm D. Skin cell with diameter of 1500 μm B and D. The unaided eye can, on average, clearly resolve objects > 100 μm 8. Label the following unmarked microscope components (numbered arrows) by matching it with the components provided (letters).   A. Stage B. Fine Adjustment Knob C. Iris Diaphragm D. Neck E. Condenser Lens F. Eyepiece G. Objective H. Base I. Coaxial Controls 1F 2D 3B 4G 5A 6H 9. For each of the following questions select from the list below the single best answer: Phase-Contrast Dark Field Fluorescence Confocal This type of microscope is best suited for visualizing GFP, RFP and YFP proteins. Fluorescence 10. This type of microscope can provide detailed images of live cells without staining. Phase-Contrast 11. This type of microscope is used to greatly increase the contrast between samples and background by reflecting light off of the specimen. Dark Field 12. This type of microscope is capable of capturing images in multiple focal planes, rendering a specimen in 3D Confocal 13. Gram-Positive cells appear……………in color due to a……………peptidoglycan layer in the cell wall. Purple; Thick 14. Gram-Negative cells appear……….in color due to a………..peptidoglycan layer in the cell wall. Pink; Thin 15. True or False: The distinguishing characteristic of Gram-Negative bacteria is the presence of LPS in the outer membrane True. 16. True or False: If you wish to study the motility of an organism you cannot heat fix, but you can chemically fix the specimen. False. Both heat and chemical fixation strategies will kill the cell, making motility observations impossible. 17. You want to observe the size and shape of a cell. What is the easiest staining technique that you could perform? Name at least one dye you would use during this process. Simple stain. You could use any of the following: methylene blue, crystal violet, safranin or fuschin. 18. You suspect a patient may have TB. Once a sample has been obtained it is sent off to the lab for an acid-fast stain. If the patient were infected with TB, describe what you would expect to see on the stained slide. You would expect to see red cells (TB+) on a blue background (TB negative). 19. True or False: If a patient is suspected of having malaria, a Giemsa stain would be an appropriate differential test to perform. True. Giemsa stains are often used in the clinical setting to aid in the diagnosis of blood parasites.