Lecture 23 - Intro to virology Flashcards
(44 cards)
why aren’t viruses living organisms?
because it cannot do anything outside a host cell
- can’t make many proteins by itself
how do viruses replicate?
they use host mechanisms and are assembled, they do not replicate by division.
how are viruses filterable agents?
they are very small and can’t be filtered the way that bacteria can
true or false, viruses contain DNA and RNA genomes
false, their genomes may be DNA OR RNA, not both.
describe general morphology of viruses
naked capsid or envelope morphology
true or false, proteins not provided by the host must be made by the virus
False, viruses cannot make proteins, but instead carry the DNA or RNA required to make proteins not provided by the host cell
viral components assemble how?
the components must self-assemble
describe virus size
the largest viruses are about the size of the smallest bacterium we know of (chlamydia)
is SARS-Cov2 an RNA virus or a DNA virus?
human RNA virus
describe the components of the basic virus structure
Nucleic acid genome covered by a capsid, which is made of capsomers.
some (typically larger ones) have an envelope, which is a membrane layer of lipids and sometimes proteins
what is a capsid/nucleocapsid
a protective protein coat for viral nucleic acids (DNA/RNA) that is formed by self assembly
how are the envelopes and envelope proteins on viruses made?
they are encoded by the virus but are made by the host
- aka spike proteins
describe the 2 naked capsid morphologies
lots of capsomer subunits bind helical nucleic acids, or
proteins assemble into pentamer capsomeres, which form an icosahedron (20 sides)
what is the most common structure of naked viruses and why?
the icosahedral structure due to its protective and stable structure.
the helical structure is very uncommon in human viruses
what are the four virus morphologies?
- helical naked capsid
- polyhedral naked capsid
- spherical (with envelope)
- bacteriophage
what are spike proteins used for?
very specific host attachment (narrow host cell spectrum)
describe how narrow the spike proteins host cell spectrum is
enough to be specific to a type of cell within a certain type of host (e.g human T cells)
describe binding of SARS-Cov2 to its specific host cell
spike protein binds to cells that carry the ACE2 receptor in airways
true or false, SARS-Cov2 would not be infectious if it didn’t have its spike protein
true
describe properties of the naked capsid
environmentally stable to:
- temp
- acid
- proteases
- detergents
- drying
what are the consequences of naked capsid viruses
- can be spread easily
- can dry out. and still contain infectivity
- can survive the adverse gut conditions
- can be resistant to poor sewage treatment
describe properties of the enveloped virus
environmentally labile and disrupted by:
- acid
- detergent
- drying
- heat
what are the consequences of the enveloped virus?
- must stay wet
- cannot survive in gut
- spreads in large droplets such as respiratory droplets, blood and breast milk
why are envelopes viruses more sensitive to heat, detergent and drying out?
because they disrupt the membrane, and if that gets disrupted, then the virus is no longer infectious and probably no longer alive