Micro 4- Viruses Flashcards
general characteristics of viruses
- obligatory intracellular parasites (require living host cells to multiply)
- contain DNA or RNA
- contain a protein coat
- few or no enzymes for metabolism (no ribosomes, no ATP-generating mechanism)
what is a host range
most viruses infect specific types of cells in one host, determined by specific host attachment sites and cellular factors required for viral multiplication
how do bacteriophages relate to host range
receptor site is part of cell wall, fimbriae, or flagella
viral size
range from 20-1000nm in length
what is a virion
complete, fully developed, infectious viral particle
viral structure:
nucleic acid
DNA or RNA but never both (either ssDNA, dsDNA, ssRNA, or dsRNA)
viral structure:
capsid
protein coat
- composed of capsomeres, protein sub units
- protects the nucleic acid from nuclease enzymes in biological fluids
- promotes virus’s attachment to susceptible host cell
viral structure:
envelope
lipid, protein, and carbohydrate coating on some viruses
- covers capsid in some viruses
- lipid, protein, and carbohydrate coating
- it is part of the host cell’s plasma membrane in some animal viruses
- may or may not be covered by spikes
viral structure:
spikes
projections from outer surface
- carbohydrate-protein complexes that project from the surface of the envelope
- allow viral attachment to host cells
- means of identification
- enable certain viruses to clump red blood cells, hemagglutination
why are capsomeres important
capsomeres are protein subunits, single or several types
-arrangement of capsomeres is characteristic of a particular type of virus
list of general morphology (shapes)
- helical viruses
- polyhedral viruses (many sided)
- enveloped viruses (spherical, helical, or polyhedral)
- complex viruses (complicated structures)
influenza classification
nucleic acid of influenza virus is in several separate segments
examples of helical virus
rabies and ebola viruses
examples of polyhedral viruses
adenovirus and poliovirus
examples of enveloped viruses and helical
influenza
examples of enveloped viruses and polyhedral
herpes virus
examples of complex viruses
bacteriophages and poxviruses
genus name ends in
-virus
family name ends in
-viridae
order name ends in
-ales
viral species is
a group of viruses sharing the same genetic information and ecological niche (host)
explain bacteriophages are grown in bacteria
bacteriophages form plaques, which are learnings on a lawn of bacteria on agar surface
-each plaque corresponds to a single virus, can be expressed as plaque-forming units (PFU)/ mL of virus plated
virus growth in living animals (in embryonated eggs)
- virus injected into the egg
- viral growth is signaled by changes or death of the embryo
virus growth in cell cultures
- tissues are treated with enzymes to separate cells
- virally infected cells are detected via their deterioration, known as the cytopathic effect (CPE)
- continuous cell lines are used
list of tests for viral identification
- cytopathic effects
- serological tests (i.e. Western Blotting)
- nucleic acids (RFLPs, PCR)
western blotting viral identifcation
reaction of the virus with antibodies