lecture 31 - viruses Flashcards
Are viruses cellular or acellular organisms?
Acellular
Why can’t viruses survive without a host?
They have no metabolic abilities of their own and rely on the bio synthetic machinery of infected cells to multiply
What is an obligate intracellular parasite?
An organism, such as a virus, that rely on a suitable host to complete their life cycle.
What are the 2 essential components of a virus?
Genetic material, capsid
What is a feature of viruses that only certain types have?
An envelope of lipids that surrounds the protein coat/capsid
What is a viral capsid?
A protein coat that surrounds, and protects the genetic material of, a virus.
What are viral capsids composed of?
Multiple units of protein building blocks called. capsomers that form a precise pattern around the virus’s nucleic acid.
What are 3 types of capsid symmetry?
Helical, icosahedral, complex
What is the structure of a helical virus?
Capsomeres coil around the nucleic acid into a tightly bound helix that resembles a tube.
What is the structure of an icosahedral virus?
The capsid is an icosahedral shape - a 20 faced polygon made up of equilateral triangles
What is the structure of a complex virus?
Contains components with different symmetries - e.g. an icosahedral head with helical tails.
How is the viral genome stored?
Nucleic acid - DNA or RNA - contained within the viral capsid
Do viruses have DNA or RNA?
Both or either
What are the possible structures of the DNA and RNA found in viruses?
Linear, circular, segmented
Is DNA and RNA double or single stranded in viruses?
Both ds and ss RNA and DNA are found in viruses.
What type of virus infects a host via the lytic cycle?
Bacteriophages
What are bacteriophages?
Viruses that infect and then replicate inside bacteria.
What is the name of the process in which bacteriophages infect bacteria?
The lytic cycle
What are 6 phases off the lytic cycle?
Attach, Penetrate, Uncoat, Genome replication & gene expression, Assembly, Release
What occurs during the attachment stage of the lytic cycle?
Phage attaches to the surface of a bacterial cell using its tail fibres
What occurs during the penetration stage of the lytic cycle?
Viral DNA is injected into the bacterial cell
What occurs during the uncoating stage of the lytic cycle?
The virus phage sheds its capsid, leaving the viral genome exposed
What occurs during the gene replication & expression stage of the lytic cycle?
DNA/RNA is replicated, transcripted and translated, and phage proteins/components are made.
What occurs during the assembly stage of the lytic cycle?
Several new phage particles are assembled from the phage components manufactured during gene expression.
What occurs during the release stage of the lytic cycle?
The bacterial cell lyses/ruptures, releasing the newly made bacteriophages.
What is the structure of a SARS-CoV-2 virus?
An enveloped virus, with linear non-segment ssRNA
What type of nucleic acid does the SARS-CoV-2 virus have?
single stranded RNA
What is the function of the spike on a SARS-CoV-2 virus?
Cell entry and attachment.
What part of a SARS-CoV-2 virus is targeted by vaccines?
The spike - to neutralise immunity
How do spike viruses bind to the surface of cells?
Receptor Binding Domain (RBD) on spike binds to an ACE2 receptor protein on the cell surface
What part of a virus spike protein binds with the cell surface of target cells?
Receptor binding domain (RBD)
What part of a cell surface will spike proteins bind to in order for a virus to infect the cell?
ACE2 receptor
Where do SARS-CoV-2 viruses replicate?
In the cytoplasm of host cells that they infect
What is HIV?
A virus - Human Immunodeficiency Virus
What disease does HIV cause?
AIDS - Acquired Immunodeficiency Syndrome
What is the structure of the genetic material of an HIV virus?
ssRNA
What is a provirus?
A component of a viral DNA/RNA that has been converted to dsDNA by reverse transcriptase and that is incorporated into the nucleus of a host cell for expression.
What enzyme is used to incorporate the genetic material of a virus into the host genome?
Viral integrase
What is a prophage?
The genetic material of a bacteriophage that is incorporated into a bacterial genome and then produce proteins if transcripted and translated.
Are viruses visible under a light microscope?
No - only visible with an electron microscope
