Summary
Summary LS10 Virology review
- Course
- Institution
A complete review of BMLS10 Virology for the K2 test
[Show more]
Seller
Follow
kelly-lan
Content preview
LS10 Virology reviewLesson 1 Viruses
A virus is an infectious, obligate intracellular parasite
★ The Latin meaning of toxin/poison
★ Virion = the infectious particle
★ Viruses are not living things, but are complicated assemblies of molecules e.g. protein,
nucleic acids, lipids, and carbohydrates, and can do nothing until they enter a living cell
(host)
★ When a virus encounters a cell, a series of chemical reactions occur that lead to the
production of new viruses → these steps are passive, but are predefined by nature of the
molecules that comprise the virus particle
Viruses are simple
★ All viral genomes are obligate parasites that can function only after they replicate in a
cell
★ All viruses must make mRNA that can be translated by ribosomes: they are all parasites
of the host protein synthesis machinery once the host takes up the virus particle
Viruses depend on their host to survive
★ If viruses are too successful and quickly kill their hosts, they immediately eliminate
themselves too e.g. omicron
★ If viruses are too passive and the host can stop their growth, then they also eliminate
themselves
★ So end phase: viruses depend on their host
Viruses are at least 300 million years old
★ Origin is unclear
★ They May have evolved from plasmids or bacteria, but unlikely that all current viruses
evolved from a single progenitor so it is thought that viruses arise multiple times
The first virus discovered: Tobacco mosaic virus (TMV)
★ TM disease stunts the growth of
tobacco plants and gives their leaves a
mosaic coloration
★ In the late 1800s, researchers
hypothesized that a particle smaller than
bacteria caused the disease → extracts
from diseased tobacco plants
transmitted the disease to healthy ones
,There are several phases within a virus
★ Eclipse phase, here there are no viral particles yet
★ Maturation phase, here only cell-associated viruses are present
★ Latent phase, the release of the virus
Virus structure
★ Their genetic material either contains DNA or RNA, the genetic material is surrounded
by a protein capsid (helical or icosahedral)
★ The capsid protects the nucleic acid from chemical, physical and enzymatic damage
★ Nucleocapsid = nucleic acid + capsid
★ Some viruses are enveloped and some are not = naked virus
Viruses use only a limited number of designs
★ Because repeating protein subunits require less genetic material
★ Capsid subunits (capsomers) are arranged symmetrically around the viral genome for
stability
★ Isohedrical has 60 subunits, and there are 20 equal triangles made of 7 proteins (T=7),
so you have a total of 420 capsid proteins (7*60=420) *EXAM Q*
Capsids are made of subunits (capsomers)
★ Necessity: nucleic acid codes for 15% of its weight as a protein, a subunit with multiple
small proteins requires a smaller gene instead of a large protein
★ Self-assembly: the structure is self-ordered and therefore corresponds to a free energy
minimum
★ Fidelity: the smaller the protein, the less chance of an error occurring
★ Economy: if more small proteins form a larger subunit, incorrectly folded proteins can
be easily discarded (minimal waste)
, Virions are metastable structures
★ Metastability = the ability of a non-equilibrium state to hold for a long time e.g.
diamonds
★ As they must protect the genome and come apart upon infection
★ They self-assemble and deliver the genome to interact with the host
Viral envelopes
★ Naked viruses are composed of only the nucleocapsid
★ Enveloped viruses have a layer of plasma membrane taken from the previous host cell
that surrounds the nucleocapsid = viral envelope, so they are derived from the host cell’s
membrane
★ On the surface of either the capsid of naked viruses or viral envelope are special proteins
and glycoproteins = spikes, they add to the attachment of the virus to a host cell
membrane
★ The viral genome does not encode lipid synthesis
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller kelly-lan. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.04. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
67096 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now