Viruses Flashcards
(36 cards)
T/F: Virus has DNA and RNA.
False: Has either or, not both usually.
True: Mimivirus.
Define Virion.
Mature infectious virus particle.
Define Capsid.
Protein shell that encloses and protects the viral nucleic acid.
Define Nucleocapsid.
T/F: Not all viruses have this.
Nucleic acid and closely associated capsid proteins.
True.
Define Envelope. What are the 3 components?
Viral membrane, consists of:
1) Lipid bilayer
2) Proteins
3) Glycoproteins
What are the 7 types of classification?
1) ds DNA
2) ss DNA
3) ds RNA
4) ss RNA +strand
5) ss RNA -strand
6) RNA viruses require a DNA intermediate for replication
7) ds DNA using reverse transcriptase
+ ss RNA acts as _____ RNA in host cell.
messenger RNA. enters and make protein right away.
All forms of DNA must make +ssRNA to be virulent. Genetic material is infectious on its own.
How does +RNA replicate?
Make -RNA and then +RNA.
What are the 3 topologies of Capsid?
1) Complex - Poxvirus
2) Icosahedral - Solid with faces, vertices and fold symmetry
3) Helical - Like alpha helix morphology.
Adenoviral has what topology?
Icosahedron with spike proteins (penton). It does not have membrane, naked and encloses the genome.
What are Matrix (M) Proteins?
Found associated with inner layer of envelope. Aid in viral structure.
What are Fusion (F) Proteins?
Found on envelope surface. Cause viral membranes to fuse with cellular membranes. This is so virus can enter host cell.
T/F: Noneveloped viruses are more resistant to disinfect than enveloped viruses.
True.
Lipid membranes are easier to disrupt, but they are essential for virus to replicate.
What are the 5 physiochemical classification of human viruses?
1) Chemical nature of nucleic acid.
2) Nucleic acid sequence similarities.
3) Presence of envelope.
4) Dimensions of virion and capsid.
5) Symmetry of nucleocapsid.
What are the 4 steps of viral infection?
1) Attachment to host cell.
2) Entry
3) Synthesis of viral proteins and genome.
3) Assembly and release.
What is the most important determinant of host specificity?
Presence of viral receptors on cell surface.
Are viruses host specific?
YES! Very, and can be tissue specific due to presence or absence of a receptor.
What receptor is present for HIV-1 and on what cell?
CD4 receptor on macrophages and t-cells. HIV-1 antigen normally binds to MHC class II mediates t-cell response.
What are the 2 coreceptors for HIV-1 that are normally chemokine receptors present on what cells?
Cxcr5 and Ccr5. On immune cells.
How does nonenveloped viruses enter?
1) Rearrange capsid protein.
2) Viruses engulfed by receptor mediated endocytosis. Partial breakup of capsid in the vacuole. Then migration into cytoplasm for further uncoating.
How does enveloped viruses enter?
1) Fusion of viral membrane cell membrane by viral F protein.
2) Phagocytosis and fusion of viral membrane with membrane of phagosome mediated by a viral F protein.
How does F protein work?
Has hydrophobic domain that can insert into the host cell membrane.
T/F: HIV is enveloped.
True
Cxcr4 is coreceptor for what cell?
Ccr5 is coreceptor for what cell?
Cxcr4 - T-cell tropic strains
Ccr5 - Macrophage-tropic strains.
