Cells are the basic
units of life. Cells are differentiated
by its structure and metabolic activities. For the study of the structure and
function of different cells, many methods are employed. Some of them are light
microscopy, electron microscopy, histochemistry, cytochemistry,
ultracentrifugation and autoradiography. Light microscopy uses a light source
and electron microscopy uses a fine beam of electrons for the image
magnification of thin tissue cells. Histochemistry deals with complete set of
tissues. Cytochemistry deals with individual cells. Ultracentrifugation is a
method which includes the study of velocities of sedimentation of various cells
of different structure through a solution. Autoradiography is a technique
employed for detecting radioactive elements within cells. Either light
microscopy or electron microscopy is used here. In the first step, living cells
are exposed to a radioactive precursor. These precursors enter the cells and
changes to macromolecules. These radioactive cells are now embedded in a resin
and thin sectioned into the slices. Now the radioactivity can be tested by
applying a photographic silver halide emulsion to the surface of the section.
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