Virus Classification Flashcards
Obligate intracellular organism
– requires a host cell to replicate
Icosahedral
-capsomers make up a multi-sided shape
Helical
– capsomers make up a coiled ribbon
Complex
– small poxvirus
Naked
– more environmentally stable (temp, acid, enzymes), survive in gut, spread by hands, fomites, droplets
Enveloped
– more environmentally unstable, must stay wet, spread via large droplets, organ transplants, blood products
Envelope
– lipid bilayer acquired by budding through membranes of host cells, contain viral glycoproteins (spikes)
Glycoproteins
– contained in lipid envelope, involved in viral attachment to cellular receptors → GP 120 of HIV
Non-structural proteins
– derived from viral genome but not incorporated into the viron structure, target of therapy (NS3 of HCV)
Receptor-mediated fusion
– virus binds to cell receptor → cell membrane and viral membrane fuse → nucleocapsid is released
Receptor-mediated endocytosis
– entire virus is endocytosed into a vesicle → release of nucleocapsid
Uncoating at the cell surface
– bind to cell receptor → viral genome only is threaded through membrane pore
RNA
– RNA transcriptase to replicate in the cytoplasm, except orthomyxoviruses use part of the nucleus
DNA
– DNA-directed RNA polymerase to replicate in the nucleus, except the poxviruses (has its own RNA polymerase)
Retrovirus
– both cytoplasm and nucleus using reverse transcriptase, to integrate into the host genome
Assembly/Maturation
– can occur in different compartments of the cell
Enveloped
– bud through nuclear membrane, ER, or cellular membrane to acquire envelope
Classification of viruses:
Order (virales) → family (viridae) → subfamily (virinae) → genus (virus) → species
DNA Viruses: HHAPPPy
Hepadna Herpes Adeno Parvo Papova Pox