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Problem 1
Fill in the following blanks.
a. 1 μm = ______ m
b. 1= _______ 10⁻⁹ m
c. 1 μm = ______ nm
Problem 2
Which type of microscope would be best to use to observe each of the following?
a. A stained bacterial smear
b. Unstained bacterial cells: the cells are small, and no detail is needed
c. Unstained live tissue when it is desirable to see some intracellular detail
d. A sample that emits light when illuminated with ultraviolet light
e. Intracellular detail of a cell that is 1μm long
f. Unstained live cells in which intracellular structures are shown in color
Problem 4
Calculate the total magnification of the nucleus of a cell being observed through a compound light microscope with a 10x ocular lens and an oil immersion lens.
Problem 5
The maximum magnification of a compound microscope is (a) ________; that of an electron microscope, (b) ________. The maximum resolution of a compound microscope is (c) ________; that of an electron microscope, (d) ________. One advantage of a scanning electron microscope over a transmission electron microscope is (e) ________.
Problem 6
Why is a mordant used in the Gram stain? In the flagella stain?
Problem 7
What is the purpose of a counterstain in the acid-fast stain?
Problem 8
What is the purpose of a decolorizer in the Gram stain? In the acid-fast stain?
Problem 9
Fill in the following table regarding the Gram stain:
Problem 1
Assume you stain Bacillus by applying malachite green with heat and then counterstain with safranin. Through the microscope, the green structures are
a. Cell walls
b. Capsules
c. Endospores
d. Flagella
e. Impossible to identify
Problem 2
Three-dimensional images of live cells can be produced with:
a. Darkfield microscopy
b. Fluorescence microscopy
c. Transmission electron microscopy
d. Confocal microscopy
e. Phase-contrast microscopy
Problem 3
Carbolfuchsin can be used as a simple stain and a negative stain. As a simple stain, the pH is:
a. 2
b. Higher than the negative stain
c. Lower than the negative stain
d. The same as the negative stain
Problem 4
Looking at the cell of a photosynthetic microorganism, you observe the chloroplasts are green in brightfield microscopy and red in fluorescence microscopy. You conclude:
a. Chlorophyll is fluorescent
b. The magnification has distorted the image
c. You’re not looking at the same structure in both microscopes
d. The stain masked the green color
e. None of the above
Problem 6
Which of the following pairs is mismatched?
a. Capsule—negative stain
b. Cell arrangement—simple stain
c. Cell size—negative stain
d. Gram stain—bacterial identification
e. None of the above
Problem 7
Assume you stain Clostridium by applying a basic stain, carbolfuchsin, with heat, decolorizing with acid-alcohol, and counterstaining with an acidic stain, nigrosin. Through the microscope, the endospores are 1, and the cells are stained 2.
a. 1—red; 2—black
b. 1—black; 2—colorless
c. 1—colorless; 2—black
d. 1—red; 2—colorless
e. 1—black; 2—red
Problem 8
Assume that you are viewing a Gram-stained field of red cocci and blue rods through the microscope. You can safely conclude that you have
a. Made a mistake in staining
b. Two different species
c. Old bacterial cells
d. Young bacterial cells
e. None of the above
Problem 9
In 1996, scientists described a new tapeworm parasite that had killed at least one person. The initial examination of the patient’s abdominal mass was most likely made using:
a. Brightfield microscopy
b. Darkfield microscopy
c. Electron microscopy
d. Phase-contrast microscopy
e. Fluorescence microscopy
Problem 10
Which of the following is not a modification of a compound light microscope?
a. Brightfield microscopy
b. Darkfield microscopy
c. Electron microscopy
d. Phase-contrast microscopy
e. Fluorescence microscopy
