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Rabu, 23 November 2011

Virus (In General)

Virus is a micro living and un-living thing. Living means it can replicate it selves. By doing the replication, virus has the behavior as a living thing. However, virus can be crystallized and it cannot do the metabolism system. Moreover, it does not have any organs like a living cell. So, virus is an un-living thing too. Its size is around 25-300 nm (1 nm = 10-9m). From its nucleic acid, virus can be classified into DNA and RNA virus.

            DNA virus is a virus which the core is structured in single or double-stranded form of DNA (Deoxiribose Nucleic Acid). DNA of the virus carries the genetic information that enables the virus to do the replication process. The well-known example of a DNA virus is Fage T virus. Based on its body, the structure of the body can be divided into three parts. The first one is the head, the tail that is coated by protein, and three pairs of stringy tail. The head of the phage T virus is protected by a protein coat called capsid. The capsid it selves protect the core (genetic material) from the harmful thing that can destroy the virus. Besides the genetic material, DNA virus sometime has several kinds of enzyme that allow it to break the membrane of the cell. The second part of its body is the tail that is coated by protein. The tail is used to transfer the genetic material when the virus successfully injecting it selves to the cell. The last part of the body is the three pairs of stringy tail. Those stringy tails are used to stick the virus to the cell especially on the membrane.
            The examples of DNA virus are grouped into Single-Stranded and Double-Stranded DNA. The single-stranded DNA is Roseola virus and the double-stranded DNA is Bacteriofage (Fage T).
            Compared to DNA virus, RNA virus has different nucleic acid and body part. The nucleic acid is structured in single-stranded form only. The genetic material is RNA (Ribosomal Nucleic Acid). The most popular model for RNA virus is HIV virus. Its body can be categorized into three parts, namely the corona that contains glico-protein, the envelope that contains protein and the genetic material (RNA as its nucleic acid). RNA virus does have enzymes. Based on HIV virus, it has the reverse transcriptase enzyme that allows it to change the form of RNA single-stranded into DNA double-stranded form. RNA virus needs the enzyme to infect the cell which has the DNA as the nucleic acid. Without that enzyme, RNA virus cannot infect the cell which has the different nucleic acid from the virus it selves. When the virus successfully infects the DNA cell, RNA will transform to DNA by using the reverse transcriptase enzyme. DNA of the virus is called prophage. After complete control over the cell, prophage will turn back to RNA single-stranded once more by using that enzyme again. RNA virus does not have hydrolysis enzyme. That’s mean it cannot break the cell.
            The examples of RNA virus are HIV, Poliovirus, Rhinovirus, influenza, Tobacco Mosaic Virus, SARS, etc.
            Virus has great roles in human’s life. As far as we know, virus can make plant, animal, even human sick and get various diseases such as AIDS, Polio, SARS, Tobacco disease, influenza, Hepatitis, and so on. However, it also gives advantages. Virus can be learned and the expertise can create vaccines to cure diseases that come from virus.

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