Properties of viruses

PHYSICAL,CHEMICAL & BIOLOGICAL PROPERTIES

1. VIRUSES: Physical, Chemical & Biological properties By, R.HARISHMA

2. A Virus is a small infectious agent That replicates only inside the living cells of other organisms It infects all plants, animals and microbes Study of virus- Virology Parasites It can’t synthesize proteins-because they lack ribosomes VIRUS

3. Genetic material- RNA [or] DNA Nucleic acid – Single [or] Double stranded Infectious viral particle called “VIRION” Structure

4. structure

5. Physical properties Chemical properties Biological properties Properties of viruses

6. SIZE: 20-300nm in diameter Parvovirus-smallest Size-20nm Poxvirus-Largest Size-400nm Plant viruses-17-200nm Animal viruses-20-350nm Physical properties

7. Size

8. The shape of virions greatly varies Ex: Rod shaped- TMV Brick shaped- pox virus Bullet shaped- Rabies virus Spherical shaped- HIV, Influenza Tadpole shaped- Bacteriophages Some viruses are irregular & Pleomorphic Shape

9. shapes

10. Three types of symmetry: Helical Polyhedral [cubical] Binary symmetry Symmetry

11. Symmetry - Types

12. Found in rod shaped virus. Capsomeres arranged in a HELICAL manner around a central axis. Ex: TMV Helical symmetry

13. Found in spherical viruses Capsomeres arranged in the form of an “ICOSAHEDRON” Icosahedron- 20 triangular sides - 12 corners - 30 edges Ex: Polio virus, Adenoviruses Polyhedral symmetry

14. Complex symmetry Found in binal viruses Ex : Bacteriophages Binal symmetry

15. Protective protein sheath that surrounds the viral genome is called a capsid. It consists capsomeres Each capsomeres consists- 1 [or] more polypeptide chain Ex : Herpes simples – 162 capsomeres Adenoviruses – 252 capsomeres Viral capsid

16. Viral particles may be, Enveloped [or] Non-enveloped Enveloped virus : Animal viruses Non-enveloped viruses : Plant viruses Bacteriophages Viral Envelop

17. Envelope – Nucleocapsid is covered by a lipoprotein membrane. It may contain glycoprotein – spikes [or] peplomers . More than one type of spikes – Influenza Triangular – hemagglutinin Mushroom shaped – neuraminidase Non-envelope – that lack envelope – naked viruses

18. Four types of nucleic acid : Single stranded DNA Double stranded DNA Single stranded RNA Double stranded RNA Chemical properties

19. All four types are found in animal viruses Plant virus – ssR ( single stranded RNA) Phages – ssD (single stranded DNA) [or] ssR Bacterial virus usually contain dsD (double stranded DNA)

20. DNA ss - Parvo viruses, phages ds - Herpes RNA ss - TMV, Retro viruses ds - Reoviruses

21. Envelope may contain glycoprotein (hemagglutinin). Enzyme – neuraminidase In bacteriophage – tips – lysozyme Protein & Enzyme

22. Viral replication can produce biochemical & structural changes in the host cell. Cell damage cytopathic effect Biological properties

23. Attachment Penetration Uncoating Replication Maturation Release Replication Cycle

24. Attachment: The virus attaches to a specific receptor site on the host cell membrane.

25. Penetration: The virus fused with the plasma membrane of host cell nucleocapsid released into the cytoplasm

26. Uncoating: Stripping the virus of its outer layer and capsid Nucleic acid is released into the cell

27. Biosynthesis: Viral synthesis depends on the type of virus. DNA Virus: nucleic acid in host cell nucleus. RNA Virus: all components in cytoplasm.

28. Assembly: Assembly may take place in cytoplasm [or] nucleus. Nucleus – Herpes & Adenoviruses Cytoplasm – Picorna & Poxviruses

29. Release: Bacteriophage – lysis Animal viruses – without cell lysis Myxo viruses – Budding from cell membrane

30. Replication

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