Virus - Structure/Function Flashcards
How much of our genome is viral?
8% is endogenous retroviruses due to ancestral infection.
Virus
Simple, miniscule, infectious, obligate intracellular parasite comprised of genetic material surrounding by a capsid and/or enveloped derived from host cell.
What is a virus composed of?
Nucleic acids and proteins
What is the base mechanism of viruses?
Hijack metabolic functions of the cell and produce their own protein viruses.
Why are viruses host obligates?
They have to hijack machinery.
iWhat genetic material do viruses contain?
ssDNA/RNA or dsDNA/RNA
What is an example of a small viral genome?
Influenza virus has 11 genes
What is the average size of viruses?
1-1000 micrometres.
What are examples of size scale of viruses?
Poliovirus same as ribosome
Rhiovirus 20-30 nm in diametre
Bacteriophage M52 24nm in size
Mimivirus 750nm
Pandoravirus 2.9MB genome
What is the difference between virus and virion?
Intracellular and extracellular for replicaiton and transmission respectively.
How are viral structures determined?
Cry-electron microscopy
Electron microscopy
X-Ray Crystallography
Nuclear Magnetic Resonance Spectroscopy
What is the structre of the viron?
Centre nucleic acid surrounded by capsomers forming capsid, together the nucleocapsids
What determines virus shape?
Arrangement of capsomers
What are the two types of capsomers?
Pentamers-5 protein subunits
Hexamers -6 protein subunits
What are the three categories of capsid shape?
Helical
Polyhedral
Binal
Helical Capsid
Where capsomers bond in a spiral fashion(Tobacco mosaic virus)
Polyhedral Capsid
This is a icosahedron carrying 20 faces and 12 corners(Adenovirus)
Binal Capsid
Irregular shapes or complex structures(monkeypox)
What is the function of the capsid?
Protects nucleic acids from enzmatic digestion, allows host cell binding thus host penetration.
What is an example of viral receptor for penetration?
ACE2
How does SARS-CoV-2 infect?
Spike proteins with ACE2 fuse with host membrane.
Spike protein
Large glycoprotein with NTD, CTD and receptor-binding domain
What happens when spike protein binds?
CC expose a fusion peptide interacting with host membrane to initate fusion.
What are the two types of virus?
Enveloped
Naked
Naked Viruses
These are absent of a membrane being more envrionmentally stable surviving wider conditions
Enveloped Viruses
These are viruses that have a lipid membrane surrounding the nucleocapsid derived from the host cell membrane
What is an example of an enveloped virion?
Cornoavirus
How do hosts differ in viral infection?
Bacteria- BP T4
Protozoa Trichomonas
Algae by Phycodnaviridae
Fungi by mycoviruses
Plants like TMV
Animals like Avian Influenza
Viruses by Virophages
What can Trichomonas infect?
Protozoa and cant infect vertebrates but CAN be sensed by them.
What can Phycodnaviridae infect?
Algae and humans
What is the structure of bacteriophages?
Icosahedral head composed of 12 pentameric capsomers and 20 hexameric capsomers
What is the genetic structure of Bacteriophage?
Linear dsDNA about 169KB long within the head connected to the tail by a neck.
What is the bacteriophage tail composed of?
Baseplate, central tube and a sheat for attachment/penetration
Why is the bacteriophage tube important?
Delivery portion of the viral genome into bacteria
What is the lytic replication cycle of bacteriophages?
Adhesion
Penetration
Replicaiton
Maturation
Release
Reinfection
What are the alternate bacteriophage life cycles?
Temperate and lysogenic phages
Temperate Phasge
These integrate into host chromosomes, producing repressor genes blocking lytic genes.
How have phages been used in biomedicine?
Bacteria resistant to antibiotics like listeria destroying listeria
