Microbiology chapter 3 pre-test
Which of the following pairs is correctly matched?
Atomic force microscopes & DNA
What does refraction mean?
A measure of the light-bending ability of medium
Place these structures of the compuound light microscope in the order that light passes through them on the way to the observer's eyes:
2) ocular lens
5) objective lens
Illuminator -->condenser-->specimen-->objective lens (ocular lens).
What is the correct order for the Gram stain process?
crystal violet--> iodine--> decolorizer--> safranin
The acid-fast stain differs from the Gram stain procedure in the decolorizing agen used. What is the reagent used in an acid-fast stain, and why is it necessary?
Acid-alcohol is used to remove the primary stain from bacteria that do not have waxy cell walls.
A student completes a Gram stain on a bacterial smear that has a mix of gram-negative and gram positive organisms but forget to apply the safranin counterstain. What would be the outcome of the Gram stain?
The gram-positive organisms would appear purple, and the gram-negative organisms would be colorless.
Which of the following is NOT visible through a compund light microscope?
In the Gram stain, what is the purpose of the counterstain?
To make gram-negative cells visible
Which of the following statements about electron microscopy & light microscopy is FALSE?
Both the electron micorscope and the light microscope use the same wavelengths for illumination.
In the Gram stain, what is the purpose of the decolorizer?
To selectively remove stain from cells
Before cells are stained, the specimen must be fixed. Fixing a specimen accomplishes all of the following EXCEPT which one?
Fixation differentiates the various cells being observed.
Which of the following staining procedures is matched with the principal use for that particular stain?
Endospore stain to distinguish dormant structures formed during adverse environmental conditions
What metric unit would be most appropriate for expressing the size of most viruses?
A student is observing a Gram stain on the 100x (oil immersion) lens. The image appears cloudy & dark. Which of the following actions will NOT increase the clarity of the image?
Lower the stage to increase the distance between the object & the objective lens.
Immersion oil is used with the 100x objective lens of the compound light microscope to ______.
prevent the loss of resolution due to refraction
Consider the following situations, and determine when a simple stain should be used instead of a Gram stain.
A microbiologist is trying to determine whether an organism has flagella.
If you use a compound light microscope, a 2-micrometer bacterial cell is best seen at which magnification?
Which of the following types of microscopy allows organisms to be identified based on antigens, even if the organisms are inside a cell?
A student is observing an object that displays the internal detail on virus at great magnification. Which type of microscope is used for this image?
Transmission electron microscope
A microscopist is studying the surface pores on a bacterial specimen. Which microscope provides the best three-dimensional surface structure image?
Scanning electron microscope
Which of the following is the most convenient & appropriate unit for expressing the size of an average bacterial cell?
* Most bacteria fall in the range of 1-10 micrometers in size.