Our present knowledge of structure and physiology of cell could be achieved only by utilizing new physic- chemical techniques and analytical instruments. Some of them are –

1. Electron Microscope – this microscope utilizes electrons as illumination source. It can magnify a cell up to 100,000 times. It has revealed ultra structure of various cell-organelles. It was designed by KNOLL and Ruska in 1932.

2. Ultracentrifuge – it is used in isolating various cell organelles or their components by centrifugation.

The tissue or cell suspension in sucrose solution is rotated at a fast speed in an ultracentrifuge. This disrupts cell walls liberating its components. The process is called cell-fractionation.


3. Chromatography – the technique is used for separation of macro-molecules and micro molecules present in cytosol left after centrifugation. The separation is based on the phenomenon of selective adsorption and differential migration of components of a mixture in a chromatographic column or on chromatographic paper.

The technique was first used by Michael Tweet in 1906 for separating the pigment of green plants.

4. Crystallography or X-ray diffractions technique – in this technique a beam of X-rays traverses the object to be studied. The diffraction pattern is recorded on a photographic plate. It helps in determining the orientation pattern of molecules, and in measuring the exact distances between these molecules. This method has helped in determining the double helical configuration of DNA molecule.

5. Autoradiography – it is a technique used for tracing the route and conventions of molecules in various biochemical reactions occurring inside the cells. Radioactive isotopes of various elements such as carbon, tritium, phosphorus, Sulfur, Iodine are widely used in cytology, biochemistry and molecular biology to understand the pathways of biochemical reactions. These radioactive isotopes are called tracers.


6. Phase-contrast Microscopy – Living cells or living tissues are often studies under phase contract microscope.