a measure of the clarity of the image; it is the minimum distance two points can be separated and still be distinguished as two points
Light microscopes can magnify effectively to about how many times the actual size of the specimen
instead of using light, focuses a beam of electrons through the specimen or onto its surface
(light microscopy) unstained specimen
passes light direct through specimen; unless cell is naturally pigmented or artificially stained, image has little contrast
(light microscopy) stained specimen
staining with various dyes enhances contrast; most staining procedures require that cells be fixed
(light microscopy) phase contrast
enhances contrast in unstained cells by amplifying variations in density within specimen; useful for examining living, unpigmented cells
(light microscopy) differential interference contrast
uses optical modifications to exaggerate differences in density, making image appear almost 3-D
(light microscopy) fluorescence
shows the locations of specific molecules in the cell by tagging the molecules with fluorescent dyes or antibodies, which then absorb UV radiation and emit visible light
(light microscopy) confocal
a fluorescent optical sectioning technique that uses a pinhole aperture to eliminate out of focus light from a thick sample, creating a single plane of fluorescence in the image
(electron microscopy) transmission electron microscopy
profiles a thin section of a specimen, revealing its ultrastructure
Disadvantages of electron microscopy
the methods used to prepare the specimen kill the cells and specimen preparation can introduce artifacts, structural features seen in micrographs that do not exist in the living cell
technique for studying cell structure and function, which takes cells apart and separates the major organelles and other subcellular structures from one another
How do the stains used for light microscopy compare to those for electron microscopy?
Stains used for light microscopy are colored molecules that bind to cell components, affecting the light passing through, while stains used for electron microscopy involve heavy metals that affect the beams of electrons passing through
Which type of microscope would you use to study the changes in shape of a living white blood cell?
Which type of microscope would you use to study the details of surface texture of a hair?