Q.Bring out the significance of Transmission Electron Microscope.

The TEM's significance lies in its extremely high resolving power, which reveals the detailed internal ultrastructure of cell organelles and macromolecules invisible to a light microscope.

A Transmission Electron Microscope (TEM) works by passing a focused beam of electrons through an extremely thin section of the specimen; because electrons have a much shorter effective wavelength than visible light, the TEM achieves a resolving power thousands of times greater than any light microscope, capable of distinguishing structures down to the sub-nanometre (near-atomic) scale.

This exceptional resolution has been of great significance to biology because it allows scientists to directly visualise:

1. The fine internal ultrastructure of cell organelles - the double membranes and cristae of mitochondria, the grana (thylakoid stacks) and stroma of chloroplasts, the cisternae of the endoplasmic reticulum and Golgi apparatus, and the nuclear envelope with its pores.

2. Macromolecular structures - individual ribosomes, cytoskeletal filaments, and even large protein complexes and viruses, which are far too small to be seen with a light microscope.

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