Ch.13 Viruses, Viroids, & Prions Part 1 Flashcards
what do viruses infect?
infect host cells and exploit them to form new virions
who is susceptible to virus infection?
cell types in all taxonomic domains
who discovered viruses?
Ivanovsky and Beijernick
what did Ivanovsky and Beijernick discover?
tobacco mosaic virus; “non-filterable particles”
what is the size range of viruses?
20 to 90 nanometers
0.02 to 0.90 micrometers
what are viruses defined as?
defined as acellular, obligate intracellular parasites
define acellular
not consisting of cells
defined obligate intracellular parasites
can reproduce/replicate only inside a host cell
what do all viruses consist of?
nucleic acid (DNA/RNA) in a protein shell, a CAPSID
comprised of capsomere units
what is the 1st step in the viral process?
Virus: host recognition
what comes from the host of the virus?
DNA polymerase & RNA polymerase (dependent on virus type)
Ribosomes
tRNA’s
nucleotides
what is the structure of capsids?
can vary in shape and size;
helical or polyhedral
define genome structure:
single or double-stranded DNA or RNA
describe enveloped viruses’ structure :
envelope surround capsid
where is the envelope derived from?
host plasma membrane
what do envelopes contain?
virus-specific proteins including glycoprotein spikes
what is the function of glycoprotein spikes?
function in host recognition and attachment
explain complex virus structure
have complicated structures; possess non-capsid protein components
ex: bacterial virus (bacteriophage)
viral genomes need what?
very specific enzymes
viral genes:
code for structural components, enzymes used in the life cycle ( viral genome replication/processing)
small viruses of viral genome encode?
< ten genes
larger viruses of viral genome encode?
> 100 genes
what does the host range mean?
how many different hosts can the virus infect?
what are the host ranges?
broad (infect many)
Ex: rabies virus
Narrow range(only infects some)
Ex:HIV infects only humans
what does infectivity depend on?
virus: host recognition
interaction between viral surface proteins and host cell surface molecules
what is tissue specificity?
infect certain types of cells or tissue within the host
the genome of DNA virus:
can serve as a template for transcription
can serves as a template for DNA synthesis
the genome of an RNA virus
can serve as a template for translation
—->(+) RNA viruses
can serve as a template for mRNA synthesis—> (-) RNA Viruses
can serve as a template for DNA synthesis —> retrovirus
what is a viral species?
is a group of viruses sharing the same genetic information and host range
the first step of viral infection
host recognition & attachment
via recognition/binding of the viral capsid, envelope proteins, or glycoprotein to host cell surface proteins/ glycoproteins
the second step of viral infection
genome entry
the entire capsid + genome enters the host cell, or only the genome may enter
the third step of viral infection
synthesis & virion assembly
genome replication, protein synthesis; assembly of virions
the 4th step of viral infection
release from host cell—> progeny infect more host cells
how are viral species classified?
classified based on genome type and the presence or lack of an envelope
what is virions?
complex viral particle
