Virus Flashcards
-has no cellular functions
-no organelles
-no nucleus
-no cytoplasm
-no cell membrane
-20 nm to 250 nm
virus
protein coat of a virus
capsid
two parts of a virus
nucleic acid and capsid
may have DNA or RNA but not both
nucleic acid of a virus
membrane-like structure outside the capsid in some viruses
envelope
parts of a bacteriophage
- head
- collar
- core
- helical sheath
- tall pins
6.hexagonal base plate
parts of Covid-19 virus
1.Major structural protein
*Spike glycoprotein (S)
*Membrane protein (M)
*Envelope glycoprotein (E)
2.Nucleocapsid protein
3. Lipid bilayer
how a virus invades a cell
- Attach
- Inject
- Integrate
4.Multiplicate
how a retro virus invades a cell
- attach
- virus core enters
- combine
- copy
- viral particles leave the cell
hypotheses that explain virus origin
1.devolution hypothesis
2. escapist (progressive) hypothesis
3. self-replication hypothesis
-viral ancestors were cellular organisms similar to bacteria
-evolved into obligate parasite
-parasites lost cellular components as it was more efficient to reproduce without
devolution (regression) hypothesis
-genetic material escaped from a free living (non-parasitic) cell and wrapped itself in protein coat
-explains viral-host specificity
escapist (progressive) hypothesis
-particles with the ability to self-replicate evolved alongside cells
-as new cell types evolved, new viruses that could target that cell evolved (co-evolution)
self-replication (co-evolution) hypothesis
process of naming viruses and placing them into a taxonomic system
virus classification
virus are classified according to
- phenotypic characteristics
*morphology
*nucleic acid type
*mode of replication
*host organisms
*type of disease they cause
two main schemes used for classification of viruses
- international committee on taxonomy of Viruses system
- Baltimore classification system
-adopted a principle that a virus species is a polythetic class of viruses that constitutes a replicating lineage and occupies a particular ecological niche
International committee on taxonomy of viruses system
-a member of a species experience evolution over time with consequent variation, but that members share a common ancestor
replicating lineage
-acknowledges that the biology of a virus, including such property as host range, pathogenesis, transmission, and habitat, are fundamental components of characterization of a virus
occupation of an ecological niche
baltimore classification was named after
David Baltimore, a Noble-Prize-winning biologist, which groups are designated by Roman numerals
