MB C3 Self Quiz

tokia's version from 2016-04-29 03:56


Question Answer
1. If a bacterium is 0.5 um wide and 15 um long how many nanometers wide is it and how many millimeters long is itWidth...0.5/m X 10-6m/ m X 10 nm/1 =5 X 10 2nm. Lenght...15mX10 6m/m X 10 3mm/1m = 1.5 X 10 2mm
2. The compound light microscope can be used to observeBActeria,cell organelles and red blood cells
3. The average wavelength of light visible to our eyes is550 nm
4. What is resolution and why is it important in microscopy(a) Resolution is the ability to see two items as separate and discrete units and is closely related to the wave lenght of light used. (b) Resolution is important to microscopy without it two separate objects would appear as one. Light of a wavelenght short enough to pass between two obkects is necessary to resolve them. If the wave lenght of lights is too long to pass between two separate objects then we would see them as one.
5. Absorptionoccurs when light rays neither pass through nor bounce off an object but are taken up by the object. Reflection occurs when light rays strike an object into our eyes
Transmissionoccurs when light rays pass through an object
Refractionis the bending of light as it passes from one medium to another different density.


Question Answer
6. In light microscopes what function does a condenser serveFocuses the light rays on the sample
7. FluorescenceLuminescnece accurs only when light rays are striking an object
DiffractionBending of light rays around an opening
Immersion oilPrevents refraction and blurry images
PhosphorescenceObject continues to emit light even after light rays no longer strike it
LuminescenceWhen absorbed light rays are changed into longer wavelengths and reemmitted
8. The total magnification of a microscope is calculated byMultiplication of the objective lens and ocular lens magnification powers


Question Answer
Phase Contrastuses visible light, but causes some light rays to strike the specimen out of phase with each other
Dark fielduses visible light rays but causes them to reflect off specimen at an angle
Bright fielduses visible light only, with light passing directly through specimen
Transmission electronuses electron beam and electro magnetiic lenses..useful for viewing internal structures of cells
Confocaluses laswer light to get thin focal-level sections through specimen resulting in 40X greater resolution and less out-of-focus light
Scanning electronuses electron beam instead of light reays and electromagnetic lenses instead of glass lenses..useful for viewing surface images of specimen
Fluorescenceuses UV light to excite molecules to emit light of different wavelenghths
Nomarskiuses visible light out of phase


Question Answer
10. What is the difference between a simple and a differential stainA simple stain makes use of a single dye and reveals basic cell shapes and cell arrangements. A differential stain makes use of two or more dyes and distinguishes between two kinds of organisms or between two different parts of an organism
11. Which of the following stains is used frequently to identify ?? and other bacteria whose cell walls contain high amounts of lipidsacid-fast stain
12. Which of the following stains is used to classify microorganisms based on their cell wall contentGram stain
13. Which of the following groups of organisms can the ?? distinguishgram-negative organisms, whose cell walls retain the mordant iodine
14. Commonly used dyes in microbiology are _____ (positively charged) or basic dyes that are attracted to negative cell components (such as in most bacterial cell walls) and anionic (negatively charged) or _____ dyes which are attracted to _____ charged cell materialCationic...acidic...positively
15. Which of the following can give you ambiguous results for the Gram stainsToo much decolorizing...Improper heat-fixing...Concenyration and freshness of the Gram-staining reagents...Cell density of the smear


Question Answer
16. The order of reagents used in the Gram stain areCrystal violet...iodine...alcohol...saframin
17. Which of the following is/are true about fluorescent microscopyFluorochromes are sometimes necessary to visualize cellular structures or cells...Antibodies can be tagged with fluorescent molecules to help visualize and prove the presence of their corresponding antigen or foreign substance such as a microbe in a blood sample
18. All of the folowing are examples of special stains exceptZiehl-Neelsen acid-?? stain
19. The presence of a capsule around bacterial cells usually indicates their increased disease-causing potential and resistance to disinfection. Capsules are generally viewed byNegative staining
20. (t/f)Special stains can efinitively help in specific identification of microbesFalse


Question Answer
21. Which of the following microscopic techniques provide three-dimensional images of a bacterial cellScanning electron microscopy
22. Describe the differences between scanning electron microscopy and transmission electron microscopysee p.68 table 3.2
23. The transmission electron microscope has the greatest resolving power because it uses an electron beam to view the sample instead of a light beam.The electron beam is used becauseElectrons have shorter wavelengths than light waves
24. Describe the process and advantages of using differential interference conrast (Nomarski) microscopy(c)Phase contrast microscopy (d)Fluorescent microscopy (b)Transmission electron microscopy (a)Bright-field microscopy (e)Dark-field microscopy (f)Scanning electron
25. Compound Microscope.Label the parts of the microscope (a) through (g) and indicate their functionsee p. 61


Question Answer
26. Phase-contrast microscopyneed answer
Fluorescent microscopyneed answer
Transmission electron microscopyneed answer
Bright-field microscopyneed answer
Dark-field microscopyneed answer
Scanning electron microscopyneed answer
27. Which of the following are true about wet mounts and the hanging-drop technoques