Can You Explain The Characteristics And Structure Of Viruses?

Characteristics: Viruses are extremely small infectious agents, which can only be seen under an electron microscope. They range in size 250 nanometer of poxviruses to the 20 nm of parvovirus. They are 10 to 100 times smaller than most bacteria, so they can pass through the pores of filter, from which bacteria cannot pass. Thus the viruses are obligate intracellular parasites. All viruses are generally resistant to broad range of available antibiotics such as penicillin.

Structure: The complete, mature and infectious particle is known as virion. The virions are composed of a central core of nucleic acid, either DNA or RNA, which is also known as the genome and is surrounded by a protein coat, the cap-Sid. Cap-Sid gives definite shape to virion. Cap-Sid is made up of protein subunits known as cashmeres. The number of cashmeres is characteristics of a particular virus. For example 162 cashmeres are present in the cap-Sid of herpes virus and 252 in the cap-Sid of adenovirus which cause some common colds.

In some animal viruses the nuclei cap Sid is covered by another membranes derived from the host cell, the envelope. Non enveloped viruses are known as naked virions. Animal and plant viruses may be polyhedron, helical, enveloped or complex.

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