PHYSICAL,CHEMICAL & BIOLOGICAL PROPERTIES

1. 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 :
o Single stranded DNA
o Double stranded DNA
o Single stranded RNA
o 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. 
i. Attachment
ii. Penetration
iii. Uncoating
iv. Replication
v. Maturation
vi. 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

31. 