Introduction To Virus

VIRUS are not plants, animals, or bacteria, but they are typical parasites of the living kingdoms. virus are not living organisms.

How Virus Reproduce ?

- without a host cell, viruses cannot carry out their life-sustaining function. They cannot synthesize protein, because they lack ribosomes and must use the ribosomes of their host cell to translate viral messenger RNA (ribonucliec acid).

- Virus cannot generate or store energy in the form of adenosine triphosphate (ATP), but have to derive their energy and all metabolic functions, from the host cell. 

- viruses are generally classified by organisms they infect, animal, plant, or bacteria. Viruses cannot penetrate plant cell walls, virtually all plant viruses are transmitted by insect or other organisms that feed on plant, based on figure 2.

figure 2 : one of the type of nematode that penetrate the leave cell wall to get the food.

In its infective form, outside the cell wall, a virus particle is called a virion. virion is a tiny, infectious particle containing a nucleic acid core with a protein coat known as a capsid. Each virion contains at least one unique protein synthesized by specific genes in its nucleic acid. Viroids ( meaning virus like ) are diseases causing organisms that contain only nucleic acid and have no structural proteins.

other viruslike particles called prions are composed primarily of a protein tightly integrated with small nucleic acid molecule.