VIRUS , VIROIDS & LICHENS

GOOD MORNING BOYS.
MARK YOUR ATTENDANCE FIRST!!

Today we will achieve the following LEARNING OUTCOMES  :-
Students will be able to :-

1.Differentiate between Virus & Viroids .

2. Analyse the discovery of Viroids  in Tobacco plant .

3. Understand the symbiotic relation in LICHEN.

4. Draw the labelled structure of TMV & BACTERIOPHAGE.


GENERAL INSTRUCTIONS :-

1. Write all the notes in your register.

2. Refer to NCERT for the topic covered today.

3. There is only one YouTube link sent along with the blog. Watch it first before reading the blog.

4. Ask your doubts ??



LET'S BEGIN








VIRUS

Pasteur. D.J. Ivanowsky (1892) gave the name virus. It means venom or poisonous fluid. According to his research, certain microbes caused the mosaic disease of tobacco.

These organisms were smaller than bacteria because they passed through bacteria-proof filters. M.W. Beijerinek (1898) demonstrated that the extract of the infected plants of tobacco could cause infection in healthy plants. He named the fluid as Contagium vivum fluidum (infectious living fluid).

W.M. Stanley (1935) discovered that viruses could be crystallised. These virus crystals are composed largely of proteins. They are inert outside their specific host cell. Viruses are nothing but obligate parasites.

A VIRUS is non-cellular, obligatory parasite (i-e; host dependent) , self-replicating genetic element consisting of DNA and RNA with no metabolic capability, but capable of transmission from host cell to host cell via a vector stage called VIRION in which the nucleic acid is encapsulated in protein coat.

VIRUS

Any of various simple submicroscopic particles of plants, animals and bacteria that often cause disease and that consists essentially of a core of RNA or DNA surrounded by a protein coat. Unable to replicate without host cell, viruses are typically not considered living organisms.

VIRION

A complete virus particles, consisting of RNA or DNA surrounded by a protein shell and consisting the infective form of a virus.

Genetic Material of Viruses

In addition to proteins, viruses also contain genetic material, that could be either RNA or DNA. No virus contains both RNA and DNA. A virus is a nucleoprotein and the genetic material is infectious. Speaking in strictly general terms, viruses infecting plants have single-stranded RNA. On the other hand, viruses that infect animals have either single or double-stranded RNA or they might have double-stranded DNA.

Bacterial viruses or bacteriophages usually have a double-stranded DNA structure. By bacteriophages, we mean viruses that infect the bacteria. The protein coat, capsid made of small subunits (capsomeres) protects the nucleic acid. They have these capsomeres arranged in various geometric forms like helical or polyhedral forms.

LITTLE INSIGHT ABOUT BACTERIOPHAGES . CLICK ON THE LINK GIVEN BELOW:

https://www.toppr.com/content/story/bacteriophages-72110/. 

DIAGRAM OF TMV VIRUS 

DIAGRAM OF BACTERIOPHAGE

Viroids

In 1971 T.O. Diener discovered a new infectious agent. This agent was more minute than the viruses. it was responsible for causing the potato spindle tuber disease. He found a free RNA. It lacked the protein coat that is found in viruses. Hence, the name viroid. The RNA of the viroid was of low molecular weight.

Lichens

Lichens are symbiotic associations i.e. mutually useful associations, between algae and fungi. The algal component called phycobiont. And, the fungal component is what we call as mycobiont. These components are autotrophic and heterotrophic, respectively.

Algae prepare food for fungi. On the other hand, fungi provide shelter and absorb mineral nutrients and water for its partner. Their association is so close that if one saw a lichen in nature one would never imagine that they had two different organisms within them. Lichens are very good pollution indicators – they do not grow in polluted areas.

RECAPITUALTION IN SHORT :

- Viruses, Viroids and Lichens
- Viruses Connecting link between living and non living.

- Non cellular structure consisting of protein coat and Nucleic acid

- Can reproduce within a host cell.

- Host cell may be killed.

- Viruses which infect bacteria are called Bacteriophage.

- Tobacco Mosaic Virus (TMV)-

- Protein coat: - capsid consists of capsomers.

- Viruses can cause diseases viz. Mumps, Small pox, Herpes, Influenza, AIDS etc.

 Viroids

- Free RNA without protein coat.

Lichens

- Composite organisms.

-Symbiotic association between Algae (Phycobiont),Fungi (Mycobiont).

THAT'S ALL FOR TODAY 

I WILL SEE YOU TOMORROW ACCORDING TO DAY 4 TIMETABLE.

NO HOME WORK TODAY .JUST COMPLETE YOUR NOTES.

ASK YOUR DOUBTS.