Structure and Chemical Composition of Viruses Flashcards
(25 cards)
smallest virus
porcine circovirus type 1
largest virus
pox virus
shapes of viruses
- filament
- bullet
- tadpole
- rod
- brick
- spherical
- pleomorphism
methods used to determine viral morphology
- electron microscope - negative staining
- cryo-electron microscopy - native environment, required liquid nitrogen
- X-ray Crystalographic method
- Nuclear Magnetic Resonance
capsid
- protein shell composed of capsomeres
helical capsid symmetry
-all animal viruses are enveloped
Icosahedral capsid symmetry
- two types of capsomeres: hexons (# varies) and pentons (always 12)
- Triangulation number - used to describe the relationship between the # of pentons and hexons
T= h2 + h x k + k2
-can be naked or enveloped
complex capsid symmetry
virons composed of several parts such as pox virus and bacteriophage
functions of a capsid
- protects viral nucleic acid
- provides the means of attachment to certain receptors
- interacts with host cell to form envelope
- responsible for uncoating genome
- transports genome
- facilitates packaging of nucleic acid
envelope
- lipid membrane aquired from the budding of nucleocapsid through a cellular membrane
- composed of:
1. glycoprotein
2. matrix protein
what are the types of envelope glycoproteins and functions?
- external glycoproteins - hemagglutination, receptor binding, antigenicity, and membrane fusion
- channel glycoproteins - alters the permeability of the membrane
what is the function of the matrix protein in the envelope?
- link the internal neucleocapsid to the lipid membrane envelope
- aids in viral assembly
- stabilizes the envelope
T or F:
Enveloped viruses are senstive and cannot last as long as naked viruses in the environment.
True
- lipid envelopes are sensitive to desiccation, heat and pH alteration
- can be inactivated or dissolved in: ether, chloroform, sodium deoxycholate, detergents, ect.
which one of the folling is not a component of a virus?
A. Nucleic acid
B. Capsid
C. Envelope
D. Capsule
D. Capsule
T or F:
the viral matrix protein is located between the viral nucleic acid and the capsid.
False
it is located between the capsid and the lipid envelope
Compare and contrast antigenic drift and antigenic shift.
- both are mechanisms of genetic diversity in viruses
- antigenic drift are genetic mutations in viral genome
- antigenic shift is the combination of two viral genomes to form new subtype
Compare and contrast recombination and reassortment.
- Both are forms of antigenic shifts.
- Recombination involves only one gene segment
- Reassortment involves more than one gene segment
which one of the following is not a mechanism of genetic diversity of viruses?
A. Reassortment
B. Point mutation
C. Recombination
D. Conjuation
D. Conjugation
- Reassortment - antigenic shift of a single gene segment
- Point mutation - antigenic drift
- Recombination - antigenic shift of multiple gene segements
retroviral integrase
- enzyme produced by retrovirus tht enables its genetic material to be integrated into the DNA of the infected cell
reverse transcriptase
- enzyme used to generate complementary DNA from a RNA template
nucleic acid polymerases
- viral genome replication
function of viral nonstructural proteins
may play roles within the infected cell during virus replication or act in regulation of virus replication or virus assembly
T or F:
nonstructural proteins are seen in extracellualr virions
False
- produced by host cell after infection
Name and describe some aberattions in virus morphology.
- incomplete virions - empty capsid
- defective virions - cannot replicate due to lack of full viral genes
- pseudovirion - contains host DNA instead of viral genome
