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BMS 127 Midterm #2 Exam Study Guide
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BMS 127 Midterm #2 Exam StudyGuide
virus - Answer obligate intracellular parasite
3 virus shapes - Answer helical, icosahedral, complex
vireon - Answer individual virus particle
3 possible components of viruses - Answer capsid, nucleic acid genome, envelope
capsid - Answer protein coat surrounding a vireon's genome
if a virus is naked, what components does it have? - Answer capsid and nucleic acid
genome
if a virus is enveloped, what components does it have? - Answer capsid, nucleic acid
genome, and envelope
bacteriophage - Answer virus that only affects bacteria
icosohedral - Answer
helix virus - Answer
complex virus - Answer
tail fiber - Answer
helical tail - Answer (B)
base plate - Answer (I)
icosahedral head - Answer (C)
why do bacteriophage look like they're crawling - Answer when complex viruses
encounter bacteria, they constantly bind and unbind (bc low affinity) until it finds it's
target
what part of the virus finds the protein target? - Answer base plate, then binds with high
affinity
what are the 2 bacteriophage life cycles? - Answer lytic and lysogenic
In the lytic life cycle of phages, what happens? - Answer the cell typically dies, releasing
many copies of the virus
,in lytic life cycle, what happens once the base plate finds the protein - Answer a
conformational change allows for the entry into the bacteria
DNase - Answer enzyme that degrades DNA
temporate phage - Answer able to enter lysogenic cycle; phage that can switch etween
lytic and lysogenic life cycles
why shouldnt we call an "envelope" a "cell membrane?" what is it? - Answer because
viruses aren't cells
the envelope is a phospholipid bilayer
what gives a enveloped viruses their narrow host range? naked viruses? - Answer
enveloped = glycoproteins
naked = capsid
how do temporate phages react to good conditions? bad conditions? - Answer good
conditions, they switch to the lysogenic life cycle
bad conditions, they swithc to lytic life cycle to get out before bacteria dies
what are the 3 mechanisms of entry of viruses? - Answer direct penetration
membrane fusion
endocytosis
what happens in direct penetration - Answer bind to protein on host, virus injects
nucleocapsid - Answer genome + capsid of an enveloped virus
do enveloped or naked viruses enter by membrane fusion? - Answer enveloped
do enveloped or naked viruses enter by endocytosis? - Answer both
endocytosis - Answer vireon engulfed by cell
what are the 2 mechanisms of viral exit? - Answer budding or lysis
do enveloped or naked viruses exit by budding? - Answer enveloped
what happens in budding - Answer viral capsid up to raft, membrane wraps/pinches
hemaglutinin - Answer mediates viral entry
neuraminidase - Answer mediates viral exit
how is HA and NA involved w host specificity - Answer HA mediates viral entry (binds to
host cell and gets thing into host cell) and NA mediates viral exit (must get out to affect
another)
, what types of hemaglutinin are human variants - Answer H1, H2, and H3
antigenic drift - Answer gradual change in HA and NA from mutations over time
antigenic drfit leads to _____ - Answer localized epidemics (AKA seasonal flus)
antigenic shift leads to ______ - Answer pandemics
why do we develop some immunity to flus? - Answer because the strain that appears in 1
year is similar to one from year before
what is the molecular basis for host specificity? - Answer glycosidic linkage between
sialic acid and galactose
in humans, what is the glycosidic linkage between sialic acid and galactose? - Answer
alpha - 2,6
in birds, what is the glycosidic linkage between sialic acid and galactose? - Answer
alpha - 2,3
different isoforms of HA and NA lead to ____ - Answer virus strains w different host
specificities
antigenic shift - Answer sudden, large change with no residual immunity
antigenic drift - Answer gradual change with residual immunity
H1, H2, and H3 can bind to ____ glycocidic linkage - Answer alpha--2,6
What did HIV evolve from? - Answer SIV
when and where do people believe HIV arose from - Answer sub-sarahan Africa in 1930s
Is HIV enveloped or naked? - Answer enveloped
in general, are enveloped virions harder or easier to catch and why? - Answer harder
because unstable outside of host cells
what determines host specificity in HIV? - Answer gp120/41,
mostly gp120
steps in HIV entry - Answer 1. GP 120 binds to CD4 component of CXCR4
2. GP 41 brings close contact and triggers membrane fusion, while GP 120 stays bound
to CD4
3. capsid enters T4 host cell
4. uncoating
mechanism of entry of HIV - Answer membrane fusion
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