Q.11 Two envelope spikes in influenza virus HA & NA stands for
- Hemagglutinin and calnexin
- Hemagglutinin and neuraminidase
- Hemoglobin and neuroserpine
- Heme and nexim
Hemagglutinin and neuraminidase are the two envelope spikes (HA & NA) in influenza virus, critical for host cell attachment and viral release respectively.
Question Breakdown
This question tests virology fundamentals, specifically influenza A surface glycoproteins—essential for microbiology and molecular biology students in topics like viral entry mechanisms and vaccine design for exams like GATE Life Sciences.
Option Explanations
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Hemagglutinin and calnexin: Incorrect; hemagglutinin (HA) is correct for receptor binding, but calnexin is an ER chaperone protein aiding glycoprotein folding, not a viral envelope spike.
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Hemagglutinin and neuraminidase: Correct; HA (trimeric spikes, ~500/virion) binds sialic acid receptors for entry; NA (tetrameric spikes, ~100/virion) cleaves sialic acid for progeny release, balancing HA activity.
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Hemoglobin and neuroserpine: Wrong; hemoglobin is a red blood cell oxygen carrier (not viral); neuroserpine doesn’t exist in virology—likely a distractor mixing neurotransmitters.
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Heme and nexim: Incorrect; heme is a porphyrin in hemoglobin/cytochromes; nexim is nonexistent—irrelevant to influenza glycoproteins.
Introduction to Influenza HA NA Spikes
Two envelope spikes in influenza virus HA & NA stands for hemagglutinin and neuraminidase, defining viral infectivity through complementary receptor binding and cleavage. These glycoproteins determine subtypes (H1N1, H3N2).
HA and NA Functions
HA mediates attachment to sialic acid on host cells and membrane fusion post-endocytosis (low pH triggers conformational change). NA hydrolyzes sialic acid linkages, preventing virion aggregation and aiding mucosal penetration.
Options Comparison
Option HA Component NA Component Accuracy Hemagglutinin & calnexin Correct (viral) Wrong (ER chaperone) Incorrect Hemagglutinin & neuraminidase Correct (attachment) Correct (release) True viral spikes Hemoglobin & neuroserpine Wrong (blood protein) Nonexistent Irrelevant distractor Heme & nexim Wrong (porphyrin) Nonexistent No virology link HA:NA balance (~4-5:1 ratio) ensures fitness.
Virology Applications
Targets for vaccines (annual strain updates) and antivirals (oseltamivir inhibits NA); crucial for pandemic surveillance and graduate-level immunology.
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