What is virus? What is structure of Virus ? And it's shape

What is virus?

The lateral meaning of virus is poisonous fluid.

Virus is minute package of DNA or RNA surrounded by protein coat or capsid.

First of all, it is discovered by D.J. Ivanowsky.

According to D.J Ivanowsky, the virus can pass easily through bacteria in filter it means virus is smaller than bacteria.

The extract of virus infected plant is able to infect another plant in which the extract of virus infected plant in injected into healthy plant which becomes infected and this fluid is called "Contagium vivum fluidum."

According to W.M Stanley virus would be crystalized and these crystal are largely made up of protein.

Virus is also called non- cellular organism because virus does not contain all the feature of cell like absence of plasma membrane as well as absence cell organell.

Virus is called connecting link between living and non- living because virus behaves as a living inside the living cell where it reproduces or multiply rapidly but when virus present outside the living cell it is unable to reproduce. Or multiplies where it behaves as a non - living that's why virus is called connecting link between living and non- living.

Virus is a pseudo proteinous structure which contains nucleic acid in the form of DNA and RNA which is surrounded by protein coat/ capsid.

Virus is a obligate intracellular parasite.

Structure of Virus:-

Virus contains three important structure:-

👉 Viral envelope:- It is membrane like structure which surrounds the virus externally which is not made up of lipid and protein.

The virus which is surrounded by viral envelope called envelope virus.

The virus which is not surrounded by viral envelope called naked virus.

The unit structure of viral envelope is called peplomere.

👉 Capsid :- Externally every virus is surrounded by Capsid / protein coat.

The unit structure of Capsid is called capsomere.

👉 Nucleic acid :-  virus must contain nucleic acid in the form of DNA and RNA.

On the basis of nucleic acid Virus is grouped into different categories,:-

👉 DNA Virus :- The virus which contains DNA as a genetic material which is found in two different form:-

1. Double stranded virus - example Hepatitis B virus, cyanophage

2. Single stranded virus :-  example phix 174, influenza virus.

👉 RNA virus :- The virus in which RNA acts as a nucleic acid / genetic material called RNA virus.

The RNA virus may be found in the two different form :- 

1. Single stranded virus - HIV ( Human Immuno Virus) , TMV ( Tobacco Mosaic Virus) 

2. Double stranded RNA virus :-  Wound Tumour virus , Mycophase 

                The virus which causes different kinds of disease called Pathogenic virus which infect different group of living being.

Shape of Virus

👉 Culrical or lcosaheatral  shapes polio virus
👉 Helical coil :- Grape shape in TMV
👉 Bacteriophage :- Capsid is polyhedral connected to help coat coil of nucleic acid 
👉 Spherical shape ( adenovirus ) 
👉 Rod shape :- TMV
👉 Coiled ( beet Yellow virus)
👉 Bullet shape ( rabies virus)
👉 Tadpole like ( bacteriophage

What is virus? What is structure of Virus? And it's shape

Pathogenic virus:-

The virus which infect other living being which causes different types of disease is called Pathogenic virus.

👉 Animal virus :- The virus which infect animal is called animal virus which may causes different types of disease.

Example :- poliovirus
Rabies ( found in saliva of dog) causes hydrophobia 
pox virus which causes chickenpox and small pox by different types of pox virus.
AIDS which is caused by HIV ( Human Immuno Virus) 
Genital herpes which is caused by herpes virus.
Genital ward ward which is caused by HPV ( Human packiloma Virus ) 

👉 Plant virus :- There are different kinds of virus which infect plant called Plant virus.
Example :- TMV ( Tobacco Mosaic Virus) which infect leaf of tobacco plant 
CMV ( Cauliflower Mosaic Virus ) 

👉 Bacteriophage :- The virus which infect bacteria called bacteriophage.

Symptoms in viral infected plant:-

The viral infected plant shows different kinds of symptoms:-
Rolling and curling of leaf. 
Yellowing and dwarfing Certain growth
Mosaic like appearance

Structure of bacteriophage

The virus which infect bacteria is called bacteriophage.

The bacteriophage was first of all discovered by Adward cwort and Felix.

It is a tadpole like structure with presence of head and tail.

The head of bacteriophage is hexagonal in shape where as tail cylindrical in their shape.

The tail of bacteriophage is attached with head with the help of collar

The head region of bacteriophage is covered with protein coat / Capsid which surrounds the genetic material i.e. DNA.

The tail of bacteriophage contains different types of structure. 

There is central hollow tube like structure.

The core is surrounded by protein sheath at the one end of tail there is presence of basal plate and fine granule along with tail fibre.

Absence of protoplasm ( which is called physical basic of life).  

The head region which is hexagonal shape 950 angstrom long and 650 angstrom width.

Shape of virus:-

Spherical ( adeno viruses)
Rod shape (TMV) 
Coiled ( beet Yellow virus)
Bullet shape ( rabies virus)
Tadpole like ( bacteriophage )

Life cycle  of bacteriophage:- 

Normally the bacteriophage / virus increases the number inside the host cell in following steps:-

 👉 Attachment of bacteriophage with the plasma membrane of host cell ( bacterial cell).

👉 Lysis of plasma membrane of host cell.

👉Entry of Viral DNA / viral DNA infected into host cell.

👉Replication of Viral DNA ( Replication of DNA )

👉 Synthesis of different types of RNA from viral genome.

👉 Synthesis of specific type of protein on the synthesis of Capsid of virus / bacteriophage.

👉The process of transcription and translation take place at same time that's why synthesis of RNA and protein take place.

👉This protein helps in formation of many Capsid inside the viral cell.

👉Viral DNA moves inside the Capsid which leads the formation of many progeny virus.

👉 After lysis / rupture of bacterial cell the progeny virus is ready to inject another cell.

                   The life cycle of bacteriophage includes two important phage:-
👉 Lytic 
👉 Lysogenic phase 

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