Title ACELLULAR LIFE.pdf ✅

ACELLULAR LIFE WORD STUDY: The word virus is derived from a LATIN word ‘VENOM’ meaning ‘POISON’  In past, the term virus was associated with infectious diseases which have UNKNOWN CAUSE VIRION: A complete viral particle is called VIRION VIROLOGY: The study of virus is called VIROLOGY STATUS OF VIRUSES: Viruses lie on the border line between living and non living things LIVING CHARACTERISTICS NON LIVING CHARACTERISTICS  Viruses possess DNA or RNA  They have the ability of reproduction  They can undergo mutation and genetic recombination  They possess the ability to infect other living things and show irritability  They are sub cellular or non cellular structure  They do not respire  They donot excrete  They can be crystallized and stored in much the same way as chemicals DISCOVERY OF THE VIRUS: eprepare.org
1800’s: By the late 1800’s pioneer bacteriologists like LOUIS PASTEUR, ROBERT KOCH had demonstrated that bacteria cause many diseases of man and other organisms. However, causal agents of some diseases puzzled them 1884: (FEDERAL BOOK) The first evidence about the existance of virus came when in 1884 CHARLES CHAMBERLAND, who worked with LOUIS PASTEUR, found that the causative agents of RABIES could pass through the PORCELAIN FILTER(which has pore sizes of 0.1 – 1 micron i.e., 100 – 1000 nm) 1892: The agent of diseases that puzzled pioneer bacteriologists could be transmitted from an infected organism to a healthy organism of the same kind. This was first demonstrated in 1892 by a RUSSIAN BIOLOGISTS named IWANOWSKY 1900: by 1900 similar disease, producing substances had been discovered in many organisms, both plants and animals 1898: ln 1898 it was demonstrated that virus from the blisters produced on the diseased stock could transmit FOOT AND MOUTH DISEASE OF CATTLE. It was given the name FILTERABLE VIRUSES, the viruses that can pass through a filter from which bacteria cannot pass 1030: By 1930 most people believed that the viruses are small particles not visible through compound microscope eprepare.org
1935: In 1935 W.M. STANLEY prepared an extract of TOBACCO MOSAIC VIRUS. Under the compound microscope, the isolated viruses appeared as SILVERY CRYSTALS composed of many rod – shaped structures. Isolated purified extracts from the cells of the hosts revealed that TMV as dead particles. This started a debate whether viruses living or dead? W.M. STANLEY took purified TMV, dissolved it in water and rubbed it on the leaves of healthy tobacco plants. The leaves soon showed the MOTTLE condition, characteristics of TMV disease. It was found that viruses had reproduced itself in living cells of the host. This proved that viruses had some living charactertics. GENERAL STRUCTURE OF A VIRUS: (FEDERAL BOOK) Primarily, a virus can be divided into two parts; (1). Core (2). Coat VIRUS PARTICLE COAT CAPSID PROTEIN ENVELOPE(NOT FOUND IN ALL VIRUSES) CORE DNA OR RNA VARIOUS PROTEINS (ENZYMES) eprepare.org
CORE: The core is inner part of virion which consists of viral genome and various proteins (enzymes) GENOME: Genome is the genetic material, which is either DNA or RNA, which may be single stranded or double stranded CORE PROTEINS: These are one more enzymes that facilitate the virus in its mode of action within the host body EXAMPLE: All single stranded RNA viruses have the enzyme transcriptase (RNA dependent RNA polymerase) to convert single stranded RNA genome into double stranded RNA genome. Retroviruses and hepatitis B virus contain the enzyme reverse transcriptase to convert single stranded RNA genome into double stranded DNA genome COAT: The coat is the outer covering of viral particle which consists of capsid and envelope CAPSID: The capsid is the protective coat of protein surrounding the core CAPSOMERS(CAPSOMERES): Capsid is composed of identical repeating subunits called capsomers(capsomeres)  The number of capsomers is specific to a particular kind of virus eprepare.org