This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Techniques – Transmission Electron Microscope”.
1. TEM and SEM are the same microscopy techniques.
a) True
b) False
View Answer
Explanation: Both Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM) use electrons to generate images but they differ by the mode of image generation. TEM uses electrons that pass through the sample whereas SEM uses electrons that are reflected or knocked off from the sample.
2. The resolving power of TEM is derived from _______________
a) electrons
b) specimens
c) power
d) ocular system
View Answer
Explanation: The resolving power of a transmission electron microscope is derived from the wave-like property of electrons that pass through the specimen. In SEM, the electrons reflect back from the specimen.
3. The cathode of transmission electron microscope consists of a ____________________
a) tungsten wire
b) bulb
c) iron filament
d) gold wire
View Answer
Explanation: The cathode of a transmission electron microscope (TEM) is located on top of the column, it contains a tungsten wire filament that is heated to provide the source of electrons.
4. The resolution attainable with standard TEM is less than the theoretical value.
a) True
b) False
View Answer
Explanation: The resolution that can be attained with a standard transmission electron microscope is about two orders of magnitude less than the theoretical value. This is due to spherical aberration of electron-focusing lenses.
5. During TEM, a vacuum is created inside the _________________________
a) room of operation
b) specimen
c) column
d) ocular system
View Answer
Explanation: To prevent the premature scattering of electrons by collision with the gas molecules, a vacuum is generated through which the electrons travel, in the column prior to operation.
6. Which of the following component of TEM focuses the beam of electrons on the sample?
a) ocular lens
b) condenser lens
c) stage
d) column
View Answer
Explanation: The condenser lens focuses the electron beam on to the specimen, in case of transmission electron microscope. The specimen is supported on the grid holder and placed inside the column.
7. Image formation in electron microscope is based on ___________________________
a) column length
b) electron number
c) differential scattering
d) specimen size
View Answer
Explanation: In case of the electron microscope, the image formation is based on the differential scattering of the electrons by parts of the specimen. The scattering of electrons is proportional to the size nuclei of the atoms that make up the sample.
8. The biological materials have little intrinsic capability to ____________________
a) scatter electrons
b) stain
c) remain viable
d) be captured
View Answer
Explanation: The insoluble materials of cells contain atoms of low atomic number such as carbon, hydrogen, oxygen and nitrogen. The biological materials therefore have very little intrinsic capability of scattering the electrons.
9. Glutaraldehyde is a ________________
a) metal
b) fixative
c) non-metal
d) atomic species
View Answer
Explanation: Glutaraldehyde and osmium tetroxide are common fixatives used in the transmission electron microscopy for the fixation of biological specimens. They stain as well as keep the sectioned specimens in a state of similarity with the living counterpart.
10. Osmium is a ___________________
a) non metal
b) heavy metal
c) alloy
d) light metal
View Answer
Explanation: Osmium is a heavy metal that reacts with fatty acids leading to the preservation of membranes. Osmium tetroxide is used as a fixative in transmission electron microscopy.
11. In TEM, the tissue is stained by floating on drops of ______________________
a) hydrocarbons
b) slow-molecular weight stains
c) heavy metal soutions
d) oil immersion
View Answer
Explanation: The tissue is stained by floating on drops of uranyl acetate and lead citrate (heavy metal solutions). These solutions when bound to the specimen, provide the density required to scatter the electron beam.
12. Shadow casting is a technique of visualizing ___________________
a) isolated particles
b) mounts
c) shoot tips
d) root tips
View Answer
Explanation: Shadow casting is a technique of viewing isolated particles. The particles are made to cast shadows after their placement in sealed chambers. The chamber contains a filament of carbon and a heavy metal.
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