Unit 4 Part 5 Viruses: Basic Structures and Functions Flashcards
what is virology
the study of viruses
unlike other microganisms (such as bacteria, fungi, and protozoa) viruses are
acellular infectious agents
obligate intracellular parasites
are viruses able to metabolize, generate energy, and multiply independently
no
what is meant by the term obligate intracellular paraistes
they must enter a suitable host in order to propogate
outside of a host cell viruses are
inert
true or false: viruses are bigger than microbes
false
what unit are viruses measured in
nanometers
what is the size range of viruses pathogenic to humans
20 - 300nm
what are two characteristics of structure every virus has
a capsid
viral genome: RNA or DNA (not both)
some viruses have extra structural components such as
replication enzymes
envelope
glycoprotein spikes
what 3 ways are viruses classified
- based on their (genome) nucleic acid types
- the presence or absence of an envelope
- capsid symmetry
what is viral capsid and what is its purpose
a protein coat enclosing and protecting the viral genome and replication enzymes from degradation
what is a viral capsid made up of
individual and identical protein subunits called capsomers
what can capsomers do during viral replication
spontaneously self-assemble into the capsid
capsomers can be assembled and arranged into precise patterns in the capsid to form two final shapes. what are they
- helical (symmetry)
2. icosahedral
in helical viruses if you were to cut the capsid into two what would you find
the two halves are identical to each other
helical viruses capsomers fit together as either a _____ or _____
spiral or helix
how do helical viruses often appear under an electron microscope
as rod-shaped
what are 3 examples of helical viruses
measles
mumps
influenza
how many sides does a icosahedral virus have
20 sided
what does each side of a icosahedral consist of regarding capsomers
21 identical capsomers arranged in the shape of a equilateral triangle
capsids of icosahedral viruses may allow what to attach to the host cell receptors
naked viruses
where is the viral genome packaged in icosahedral viruses
inside the capsid
the viral genome inside the capsid or a icosahedral virus is known as what
nucleocapsid
what is the viral envelope made of
proteins and host cell membrane (phospholipids) that enclose the nucleocapsid
is the viral envelope found in all viruses
no, only some
what can the viral envelope have on it
surface projections called glycoprotein spikes
what do glycoprotein spikes on a viral envelope allow for
attachment to specific host cell surface receptors
facilitate the release of newly created mature viruses from infected cells
enveloped viruses are more susceptible to what then naked viruses
chemical biosides such as alcohol
what is a notable virus with a viral envelope that contains glycoprotein spikes
HIV
in the HIV virus what does the glycoprotein spike do
gp120 binds to CD3 receptor on T helper lymphocytes in humans
How many types of glycoprotein spikes does influenza virus have
2
hemaglutinin (aka H or HA spikes)
Neuraminidase spikes (N or NA)
what is the role of the hemagglutinin (aka H or HA) spikes in the influenza virus
spikes attach to the receptor sialic acid on cells in the respiratory tract
what is the role of the neuraminidase (N or NA) spikes in the influenza virus
cleave and release the viral progeny from the infected cell to promote spreading
how many types of influenza virus are there
2 Type A and type B
Type A influenze can be classified into subtypes based on what
according to the H and N spikes
how many strains does the 2016-2017 vaccine contain
3
different H spikes on the influenza virus determine what
host specificity and range
what subtypes are the most common caues of human flu
H1, H2 & H3
whats the difference between the swine flu and the avian flu regarding receptors
swine flu: H1 receptors bind to cells in the upper respiratory tract
avian flu: H5 tends to bind to cells in the human lungs
what has limited transmission between humans between swine flu and avian flu
swine flu is more contagious because they latch in the upper respiratory tract
true or false: some viruses carry replication enzymes with them
true
what is an example of a virus that carries replication enzymes
HIV
carries: reverse transcriptase and protease (targeted by antiviral drugs)
can viruses contain both DNA and RNA
no, one or the other
true or false the virus genome is single stranded
false, viral genome can either be single stranded or double stranded
i.e. ssDNA, ssRNA, dsDNA or dsRNA
the type of DNA or RNA and its polarity of the viral genome can influence what
how they multiply in the host cell
what does the coronavirus cause
sars and the common cold
