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Microbiology, Fifth Edition
Microbiology, 5/e
Lansing M Prescott, Augustana College
Donald A Klein, Colorado State University
John P Harley, Eastern Kentucky University

The Study of Microbial Structure: Microscopy and Specimen Preparation

Multiple Choice Quiz

Choose the best answer


The substage condenser
A)changes the wavelength of the light reaching the specimen
B)focuses light on the specimen
C)decreases the amount of light reaching the specimen

A 40X objective and an 10X ocular produce a total magnification of

Living, unstained cells and organisms can be observed best using
A)fluorescent microscopy
C)phase contrast microscopy

Scanning electron microscopy (SEM) is best used to study
A)small internal cell structures.
B)surface morphology.
C)all of the above.

A microscope in which an image is formed by passing an electron beam through a specimen and focusing the scattered electrons with magnetic lenses is called a
A)transmission electron microscope
B)scanning electron microscope
C)phase-contrast microscope

Resolution is the ability of a lens to distinguish between small objects close together. What approximate resolution can be obtained with a lower power (10X, N.A. 0.25) objective lens?
A)0.2 microns
B)0.3 microns
C)0.9 microns

Fixation is the process by which the structures of the cells are preserved and fixed in position. An advantage of chemical fixation over heat fixation is that it
A)magnifies the specimen
B)does not destroy internal structures

Monochromatic (one color) light is sometimes used to increase the resolution of light microscopes. Light of which color below would give you the best resolution?

Which of the following objectives would give you the best resolution of small objects?
A)10x air, N.A. 0.25
B)40x air, N.A. 0.65
C)64x oil, N.A. 1.4
D)100x oil, N.A. 1.25

Transmission electron microscopy is best for high magnification viewing of
A)internal structure of fixed cells.
B)internal structure of live, motile cells.
C)surface structure of fixed cells.
D)surface membranes of live, motile cells.

Which of the following statements is most correct about the differential Gram stain?
A)Crystal violet differentially stains Gram positive cells.
B)Gram's iodine differentially stains Gram positive cells.
C)Acetone differentially destains Gram negative cells.
D)Saffron red differentially stains Gram negative cells.

Which of the following statements is most correct about Atomic Force Microscopy (AFM)?
A)AFM can visualize protein bound to DNA molecules.
B)AFM can visualize unfixed specimens in water or buffer.
C)AFM moves a very sharp tip over the surface of the specimen to "feel" its shape.
D)All the statements above are true.

Which of the following statements about Transmission Electron Microscopy is not true.
A)The specimen must be stained with osmium or other heavy metal.
B)The specimens are placed in a high vacuum for viewing.
C)The specimens must be sliced very thin, 20-100 nm in thickness.
D)The beam is focused by electromagnetic lenses.

Phase Contrast microscopy
A)Continuously changes the phase of the incident light from the condenser to improve contrast in the specimen.
B)Uses circular filters in the condenser and objective to give contrast to parts of the cell with different refractive indices.
C)Uses special lenses to distinguish between solid and liquid phases of the cell.
D)Uses special lenses to change the color of light passing through them.

Differential Interference Contrast microscopy
A)compares two identical specimens on the same microscope.
B)illuminates the specimen with light of two different colors.
C)illuminates the specimen with light of two different phases.
D)illuminates the specimen with both reflected and transmitted light.

Which of the following is NOT equivalent to 10 micrometers.
A)0.0001 cm
B)0.01 mm
C)10,000 nm
D)100,000 Angstroms

"Parfocal" refers to microscopes with multiple objectives where
A)objectives are used in pairs for stereoscopic effects.
B)each objective has the same working distance above the specimen.
C)each objective is positioned to be in focus at the same stage height.
D)sequential objectives increase power by a factor of two.