1/24 Kingsley Basic Virology Concepts - Structure and Function Flashcards
Viral size limits function, so they have _____ and are _____
- no intrinsic metabolism
- obligate intracellular parasites
What is a virion?
Infective viral particle
Non-enveloped viruses contain what structures?
Nucleocapsid and capsid
What is a nucleocapsid?
Nucleic acid core
What is a capsid?
Protein shell (contains the viral DNA inside)
Enveloped viruses are derived from:
Host membrane
includes viral proteins in membrane lipids
In enveloped viruses, the “envelope” is ____ to the nucleocapsid
External
Viral capsid structure is often:
Pentamers or capsomeres
Capsomere is a structural unit of:
(nucleo)capsid
One of the functions of the viral capsid is delivery via ______
VAPs
What are VAPs?
Viral attachment proteins
_____ are naked and are released by cell lysis
Non-enveloped viruses
_____ are released by budding
Enveloped viruses
Enveloped viruses are less stable, so they must be:
Wet (must stay wet)
All human helical viruses are:
Enveloped
Viral envelope composition
- Host derived lipoproteins surround nucleocapsid
- Viral glycoprotein (peplomers, VAPs)
Peplomers are ____ which have ____
Viral spikes; tissue specificity
Viral glycoproteins (peplomers) may function as:
VAPs (viral attachment proteins)
Examples of viral glycoproteins
- Hemagglutinins
- Neuraminidase
“H” and “N” of H1N1 influenza virus
Neuraminidase enables ____ from cell by _____
Viral release; cleaving terminal neuraminic/sialic acid
_____ has both hemagglutinins and neuraminidase
H1N1
Viral recognition is dependent on:
- host range
- tissue tropism
Why is host range important in viral recognition?
VAPs may restrict which host(s) is/are infected
VAP-receptor may further restrict cell type that can be infected, due to:
Tissue tropism
Capsid VAPs or envelope VAPs have:
Tissue tropism
_____ viruses are sufficient to cause infection on their own
DNA and (+) RNA strand
For RNA viruses, the _____ strand is sufficient to cause infection on its own
Positive (sense)
For a (-) RNA virus, _____ is needed as an intermediate step to cause infection
RNA dependent RNA polymerase
____ viruses can get into the nucleus, whereas ____ viruses cannot and stay in the cytosol
DNA; RNA
Most human DNA viruses are:
dsDNA
Human dsDNA viruses replicate in:
Nucleus
Most human RNA viruses are _____
ssRNA
Human ssRNA virus replication occurs in:
Cytoplasm
Baltimore classification: Group II
single stranded DNA (ssDNA)
Example of Group II virus
Parvovirus (ssDNA)
Baltimore classification: Group III
Double-stranded RNA (dsRNA)
Example of Group III virus
Rotavirus (dsRNA)
Early phase of viral replication includes:
- recognize target cell
- attach via receptors (capsid, envelope)
- penetrate or cross plasma membrane
- uncoat in cytoplasm or delivered to nucleus
Late phase of viral replication includes:
- genome replication
- viral protein synthesis
- assembly
- release (lysis, budding)
Routes for viral uptake
- endocytosis
- fusion
- translocation (viropexis)
____ viruses can be taken up by a cell via endocytosis
Naked or enveloped
_____ is a route for successful infection for some viruses
Endocytosis
Endocytosis may prevent:
Infection by other viruses
What is fusion?
Envelope (of enveloped virus) merges with membrane to release capsid
Fusion occurs in _____ viruses
Enveloped (only)
Example of translocation mechanism
Viropexis
What is viropexis?
- binding exposes hydrophobic structures
- allows viral entry into host cell
DNA viruses use _____ for transcription
Host DNA-dependent RNA polymerase II
RNA viruses use _____ for transcription
viral RNA-dependent RNA polymerase
DNA viruses use ____ for replication
Host DNA-dependent DNA polymerase
RNA viruses use _____ for replication
Viral RNA-dependent RNA polymerase
How are naked viruses released from the cell?
Lysis (sudden release)
How are enveloped viruses released from the cell?
Budding (slow, gradual)