chapter 5 objectives Flashcards
what does it mean to be filterable
they are smaller than bacteria and able to pass through filter designed to trap bacteria
size of virus compared to microorganisms
20nm up to 1000nm
6 characteristics of virus
10x number of bacteria/archae, ubiquitous, protein shell surrounds nucleic acid core, DNA or RNA (not both), high specificity/tropism, multiplication
tropism
high specificity
4 ways viruses are named
hosts and diseases they cause
structure
chemical composition
genetics
3 methods to grow viruses
Egg culture
Cell culture
Animal inoculation
2 types of viral capsids
made of a protein subunits called capsomeres
helical viruses and and icosahedral viruses
enveloped vs naked viruses
enveloped: surrounded by an envelope and nucleocapsid
naked: only composed of nucleocapsid
importance of viral surface proteins
pikes help a virus attach and penetrate into its host cell
types of nucleic acids viruses contain
DNA: single-stranded or double stranded
RNA: can be double stranded, but usually single stranded
+ RNA, -RNA
virion
fully developed viral particle
5 step life cycle of viruses
adsorption, penetration/uncoating, synthesis, assembly, release
adsorption
invasion of a cell with virus
penetration/uncoating
cell membrane penetrated by whole virus through endocytosis/direct fusion
endocytosis
entire. virus engulfed by cell
direct fusion processes
envelope merges directly with cell membrane
synthesis
replication and protein production
DNA–>nucleus
RNA–>cytoplasm
assembly
put together parts manufacture during synthesis process
release
the number of viruses released by infected cell
cytopathic effect
virus-induced damage to the cell that alters its microscopic appearance, ex. inclusion bodies (compacted viruses)
acute infection
sudden onset of a disease and can also be resolved rather quickly
persistent infection
latent or chronic;
latent:cell harbors the virus and is not immediately lysed
chronic: virus remains and multiplies at low low levels
transforming infection
characterized by increased rate of growth and changes in chromosomes or cell’s surface
oncogenic virus
cancer-causing virus
ex. hepatitis B virus
5 stages of t-even bacteriophage replication
adsorption: binding bacteriophage to host cell
injection of phage DNA
synthesis of phage
assembly
release
lysogenic cycle
condition which the host chromosome carries bacteriophage
lytic cycle
cells lyse to release new viruses
lysogenic conversion
when bacterium acquires a new trait from its template phage
3 noncellular infectious agents
prions, satellite viruses, viroid
prion vs virus/bacteria
prions not containing nucleic acids and are made entirely of misfolded proteins
reason why antiviral drugs are more difficult to design than antibacterial drugs
replication of viruses, rapid genetic variability, lack of specific viral targets, complexity of viral life cycle
