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Discovered the first vaccines for rabies.
Proposed the term "virus"
Unique group of biological entities known to infect every type of cell.
- Unusual strucure and behavior
- Infectious particles.
- Obligate intracellular parasites
You can see virus
Type of viruses
Naked virus.: CONSIST OF ONLY A NUCLEOCAPSID
Enveloped virus:ADDIONAL COVERING EXTERNAL TO THE CAPSID
Protective outer shell that surronds viral nucleic acid.
Capsid spikes are used for attachement to host cells.
- 2 types of capsids.
- Form a continuos helix.
- Nucleic acids coils inside
Types of Helical viruses
- Naked Helical.
- Enveloped helical
Naked helical virus
- -Tobacco mosaic
- -Nucleocapsid is rigid and tighly wound into a cylinder shape package
Enveloped helica virus
- -Inglueza, measles, rabies.
- -Nucleocapsid is more flexible.
- -Enveloped come from host cell membrane
- -Variation in capsomer number
- Polio virus 32 capsomer
- Adenovirus 240 capsomer
Types of Icosahedral viruses
- -Naked icosahedral viruses.
- -Enveloped Icosahedral virus.
- Envelope como fron host cell membrane
- -Animal viruses.
- -Lipid and proteins.
- -Envelope spkies fro attachament of viruses to the next host cell
- -Enables pleomorphic shape of viruses
Function of capsid/envelope
- -Protect nucleic acid from the host's acid and protein digestive enzymes
- -Asist in binding and penetrating host cell
- -Stimulate the host's immune system
- -Intricate structure
- -Pox virus
- 1 virus can infect 1 cell @ the time.
- Only the DNA gets to the cell
- -Viruses contain either DNA or RNA but not both
- -Posess only the genes to invade and regulate the metabolic activity of host cell
- -No viral metabolic genes
- - Adsoption ( Attachment):The virus attaches to it host cell by specific binding
- Viral attachment to host cell is mediated by spike protein
- -spikes recognize only certain host receptors.
-Naked viruses are endocytosed( requires degradation of cell membrane and capsid prior to uncoating)
- -Enveloped viruses
- viral envelop fuses to host cell membrane.
Allow only capsid to directly enter cytosol
Release of Enveloped viruses
- -Liberated by bundding or exocytosis
- allows them to retain a portion of the host cell membrane
Damage to the host cell due to a viral infection
Virus that specifically infects bacteria
- -Viral enzymes weaken host cell membrane
- -leads to rupture the cell (lyses)
- -Realse numerous virion
Insertion of viral DNA into the bacteria host genome.
Allows viral DNA to be copied with every cell diviision of bacteria
Cultivating Animal viruses
Eggs provide an intact self-supporting unit for viral maintenance
Normal Vs Infected cells
- -Normal cells form an enven monolayer of undisturbed cells
- -forms visible plaques
Noncellular Infectious Agents
- satellite viruseed
-protein particle with no nucleic acid, no envelope, no capsid
Dependent on other viruses for replication
- -Plant pathogens
- tomatoes, potatoes, cucumbers
- -Naked strands of RNA, no capsid
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