Virus’s Flashcards
What is a virus
A very small infectious, obligate intercellular parasite
- needs a host cell to carry out genome replication
What are progeny virions formed for
They’re formed in host cells as a means of transmission on virus to the next host cell
What do host cells provide that virus’s need
Nucleotide for nucleic acid production
- amino acids for translation of proteins
- ribosomes for translation of proteins
- ATP for energy
- Golgi for protein processing
- endoplasmic reticulum for protein processing
What are viruses classified by
Whether they have DNA OR RNA
- what type of capsid symmetry they have (helical, icosahedral, complex)
- whether they’re naked or have an envelope
- genome characteristics
What are viruses made up of
.a nucleic acid (DNA or RNA)
- protein coat (capsid) surrounding nucleic acid
- sometimes an envelope
- sometimes a capsule
What are the features of virus nucleocapsid
’ They’re highly symmetrical
Composed of one protein ( capsid protein)
Capsid is formed by self assembly of the capsomeres
What are bacteriophages
They infect and replicate within bacteria
- complex structure
- classified by shape and nueleic acid
What is the bacteriophage structure composed of
Head, collar, tail, tail pins, tail fibres
What are the 5 stages in thebacteorophage life cycle
Attachment
Penetration
Synthesis of nucleic acid and protein
Assembly and packaging
Release ( lysis)
What occurs in the attachment stage of bacteriophage life cycles
All virus’s have attached proten’s
- they’re found on the outside of virus’s
This protein attaches to specific receptors on host cell surface
Virus receptors are normal proteins found on outside of host cell
● Part of the host immune response is against this attachment protein
The tail fibres attach to proteins on the outside of the virus
Bacteriophages penetrate their nucleic acids into the host e
What is the lytic cycle
Infected bacteria are production factory for lambda
bacteriophage and are lysed to release new bacteriophages
What is the lysogenic cycle
What’s an example of a plant virus
Tobacco mosaic virus
What are the different types of cell culture
Primary cell culture, Diploid cell lines, Continuous cell lines
Enveloped Virus Life Cycle
Envelope is lipid bilayer with glycoprotein spikes
Virus envelope fuses with cell membrane
Synthesis of nucleic acid genome and viral proteins
Endoplasmic Reticulum of cell makes viral glycoproteins
Site of virus assembly varies (golgi complex, nuclear or cell membrane)
Progeny viruses bud from the cell (similar to exocytosis)
Cell membrane remains intact - does not kill host cell
Virus Glycoproteins- properties
Matrix protein links virus nucleocapsid to membrane
Virus glycoproteins are inserted in membrane
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Form spikes on outside of virus
Main antigens for immune system
