Study of cell ultrastructure

A cell is a basic unit of any organism. Its volume ranges from a few attolitres (bacteria) to milliliters (nerve cells of squid). Structure and metabolic activities changes from cell to cell. Cells usually assume flexible structures with a delimiting dynamic membrane in an undulating state. Diffentiation is a process where the development of a stem cell into cells with spaecialized function takes place. For example, in the case of a fetus, single cell is resulted from the fusion of one spermatozoon and one ovum. This fusion leads to the formation of a vast array of different tissues. For the study of structure and functioning of cells, many methods are used. They are optical microscopy, electron microscopy, histochemistry, cytochemistry, autoradiography and ultracentrifugation. Optical microscopes use light and can be used to identify cells. But fine structure of cells and very tiny cells are not coming to the frame optical microscopes. For this, electron microscopes are used. There are many types of electron microscopes. There are many varieties in electron microscopes. Some of them are scanning electron microscopes, transmission electron microscopes and scanning probe microscopes. Histochemistry deals with whole tissues and cytochemistry with individual cells. Autoradiography is a method used for identifying and locating radioactive compounds within cells. Ultracentrifugation is a method of fractionation of the cells which is required for the study of biochemical activity of subcellular organelles.