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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