How Viruses Work: Virology

Morphology Factors

Virus Shapes

Early investigation with tobacco mosaic virus (TMV) firmly recommended that viruses were composed of repeating subunits of protein which was later supported by crystallization of TMV. A significant progression in determining the morphology of the virus was the advancement of negative stain electron microscopy. Another adjustment of classical electron microscopy is cryo-electron microscopy where the virus-containing samples were quickly frozen and analyzed at an exceptionally low temperature; this permits us to preserve the native structure of the viruses.

A virion is a complete virus particle that is surrounded by the capsid protein and encapsulates the viral genome (DNA or RNA). At some Point structure without nucleic acid can be visible under the electron microscope those structures are called unfilled capsids. In some of the viruses like paramyxoviruses the nucleic acid is encircled by the capsid proteins and the composite structures allude as the nucleocapsid. Some of the viruses contain the lipid envelope which encompasses the nucleocapsids. The envelopes are gotten from the host cell membrane during the budding process. As the envelopes are derived from the host cell membrane, they contain a significant number of the surface proteins present in the host cells.

There are two sorts of symmetry found among the viruses: icosahedral and helical. In theory of the icosahedral symmetry may at some point referred a spherical based on the external morphology. Icosahedral symmetry has 30 edges, 12 vertices, and 20 faces. They additionally have two, three, or fivefold symmetry based on the rotation through axes passing through their edges, faces, and vertices separately. The viruses of this sort look spherical in shape. The viruses of this kind look rod-like or filamentous. The viruses which contain enormous DNA genomes are more complex in structure, for example- poxviruses and herpesviruses.

 Virus Size

Viruses are commonly much smaller than the bacteria and its average size varies from 25-300 nm in diameter. They are noticeable under an electron microscope and only the biggest and complex viruses are seen under a light microscope with high resolution.. As of late, scientists confined a new form of the virus that contaminates amoeba and assembled it under a different family Mimiviridae. The family belongs to the Mimiviridae which is a scale from 400-800 nm in diameter.

On average a bacterial cell is around 1400 nm in diameter although an average epithelial cell is about 20,000 nm. Examining both viruses and bacteria to be almost round a bacterial cell has a volume of about 30,000 times greater than a virus while an epithelial cell is about 60 million times larger.