Lecture 5: Structure & Function of Viruses Flashcards
What is a virus particle called?
A virion
What are viruses?
Acellular microorganisms which have no metabolic abilities of their own and require a host to survive.
How do viruses reproduce?
They rely on the biosynthetic machinery of a host to reproduce.
How big are virions?
10-400nm
What 3 things does a virion consist of?
- Genetic Material (DNA or RNA)
- Capsid (protein coat) which surrounds and protects the genetic material.
- An envelope of lipids which surrounds the protein coat when the virion is not in a host cell. [IN SOME CASES]
What is a capsid?
A protein coat which surrounds and protects the genetic material of a virus.
What is a nucleocaspid?
Nucleic acid surrounded by the capsid.
What units are capsids built of?
Capsomer ‘building blocks’
What kinds of shapes/symmetry do viruses have?
- Helical
- Icosahedral
- Complex
What type of symmetry does a bacteriophage have?
Complex
Do viruses infect eukaryotes or prokaryotes?
Both! They infect ALL forms of life.
What are five stages in a virus life cycle?
- ATTACHMENT of the virion to the host cell (‘lock + key’ fit).
- ENTRY of the bare nucleocaspid into the cell.
- SYNTHESIS of viral components ie. genome and proteins.
- ASSEMBLY of viral components into progeny virions.
- RELEASE of the progeny virions from the cell.
What do bacteriophages do?
They infect and replicate bacteria. For this reason, they used to be used to treat bacterial diseases.
What is lytic (virulent) infection?
Host cell dies after progeny are released.
What is lysogenic (temperate) infection?
Host cell survives, genetic material is either free in cell’s cytoplasm or integrated into the Lysogen’s genome (lysogen replicates with virion’s genetic material).
Prophage is capable of producing lytic phage.
What is the form of phage that causes a lysogenic infection called?
Prophage
In lytic infection, how many virions released at the burst size?
100-200
What is lysogeny?
“The relationship between the temperate phage and host bacterium”
In response to a signal, lysogenic phages enter a _____ cycle.
In response to a signal, lysogenic phages enter a LYTIC cycle.
Is HIV an enveloped virus
YES
How many strands of RNA does HIV have?
2
Is HIV lysogenic or lytic?
Lysogenic, but also is lytic at times in its life cycle. It integrates into the genome (by creating DNA from its viral RNA using an enzyme).
