Introduction to Microscopy Flashcards
In what two ways to light microscopy and electron microscopy differ?
- Optical resolution
- Available magnification
Light microscopy and electron microscopy differ in ______________ _____________ and ____________ ___________.
Optical resolution
Available magnification
What does “resolution” mean in practical terms?
The capacity of an optical system to reveal detail in a specimen
What is the optical resolution of a typical light microscope?
0.2 µm
What’s the optical resolution of an average electron microscope?
1 nm
What is the available magnification of an average light microscope?
1000X
What is the available magnification in an average electron microscope?
100,000X
What are the two types of electron microscopes?
- Transmission
- Scanning
_______________ EM produces three-dimensional images, but these are restricted to the surface of the object with the internal structure concealed from view.
Scanning
__________________ EM is so named be ause the electron beam must pass through the specimen, which has been cut into ultrathin sections, resulting in a two-dimensional image of section planes.
Transmission
Which electron microscopy is more informative? Transmission or scanning?
Transmission
What is the available area with which one can view under a light microscope?
Several cm2
What is the available area with which an electron microscope can provide?
Less than 1 mm2
What are three ways in which electron microscopy is less flexible than light microscopy?
- The available area is generally less than one square mm
- Few staining methods are available, producing only black and white images
- Costly and time-consuming, thus not available to most students
Electron-dense describese the relative ________________ of an image of a transmission EM.
Darkness
Electron-lucent describes the relative _______________ of an image in electron microscopy.
Lightness
One major group of specific methods known as ________________ techniques employes reagents known to react with defined cellular constituents (e.g., lipids, glycogen and DNA), thereby producing selective coloration recognizable by light microscopy.
Histochemical
In a subset known as _______________ histochemistry, the activity of ________________ can similarly be demonstrated by staining for their specific substrates or end products.
Enzyme
Enzymes
_____________________ is immunologically based in which antibodies are raised against specific cellular components (i.e., antigens) and then conjugated with a visual marker appropriate for LM or EM.
Immunohistochemistry
What is a problem common to both light and electron microscopy?
The need to prevent autolytic degeneration and to preserve cellular ultrastructure
_________________ causes cross-linking of macromolecules, which reduces and arrests biological activity, at the same time rendering the cells more amenable to staining.
Fixation
Fixatives such as ______________ and __________________ are used to prevent autolytic degeneration and to preserve cellular ultrastructure.
Formaldehyde
Glutaraldehyde
Most tissues are too thick to be examined directly in the microscope and thus must be _____________ into thin slices. To faciliate cutting of these thin slices, the tissue is usually ______________ in a hard medium like parrafin wax or plastic resin. Fixed tissues generally require _______________ with organic solvents before this step.
Sectioned
Embedded
Dehydrated
What are artefacts?
Distortions in cell and tissue architecture
