Chapter 6

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

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.
• -helical
• -icosahedral

• Form a continuos helix.
• Nucleic acids coils inside

• Naked Helical.
• Enveloped helical

• -Tobacco mosaic
• -Nucleocapsid is rigid and tighly wound into a cylinder shape package

• -Inglueza, measles, rabies.
• -Nucleocapsid is more flexible.
• -Enveloped come from host cell membrane

3 dimensional.

• -Variation in capsomer number
• Polio virus 32 capsomer
• Adenovirus 240 capsomer

• -Naked icosahedral viruses.
• Papillomavirus

• -Enveloped Icosahedral virus.
• Herpes.
• 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

• -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
• -Bacteriophage
• 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
• -Penetration
• -Synthesis
• -Assembly
• -Release

• 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

• -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

Eggs provide an intact self-supporting unit for viral maintenance

• -Normal cells form an enven monolayer of undisturbed cells
• -forms visible plaques

• prions
• satellite viruseed
• viroids

-protein particle with no nucleic acid, no envelope, no capsid

• -Diseases
• Mad cow

Dependent on other viruses for replication

• -Plant pathogens
• tomatoes, potatoes, cucumbers
• -Naked strands of RNA, no capsid