H2 Biology 14 - Virus structure

genetic material(RNA or DNA)

capsid; protein coat surrounding DNA/RNA of virus

envelope(may/may not be present) >

viruses w/ capsids, surrounded by envelope -> enveloped viruses

viruses w/o envelopes -> naked/non-enveloped viruses

8 segments of ssRNA genome, RNA-dependent RNA pol enclosed within capsid >

RNA-dependent RNA pol enters host cell, catalyses synthesis of complementary RNA strand >

glycoprotein spikes(haemagglutinin(HA) neuraminidase(NA)) project from envelope's outer surface >

HA r&b to specific receptors on plasma membrane of host cells;

NA facilitates exit & release of newly replicated viruses from infected host cell by budding

enveloped retrovirus, 2 copies of ssRNA tightly bound to nucleoproteins >

retrovirus replicate by reverse transcription of viral RNA->DNA >

within capsid;

reverse transcriptase; synthesises complementary DNA from viral RNA template, cDNA used as template for synthesis of 2nd DNA strand, forms dsDNA

integrase; enzyme integrates dsDNA into host cell's DNA

HIV protease; cleaves immature HIV polyprotein into individual functional viral proteins >

capsid surrounded by envelope formed from host's CSM >

glycoproteins(gp120, gp41) protrude thru envelope >

gp120, specific conformation, allows virus to r&b to specific receptors on host cells CSM >

gp120, gp41 association w/ host cell receptors leads to fusion of HIV envelope & host CSM

icosahedral capsid, encloses linear dsDNA molecule; not enveloped >

protein tail sheath attached to capsid, has tail fibres used to recognise & adsorb onto specific receptor sites on host bacterial cell wall

icosahedral capsid, encloses linear dsDNA molecule >

tail sheath only 1 tail fibre

virus contains DNA/RNA, functions as genetic material of virus >

genes code for synthesis of viral components(DNA/RNA, viral enzymes, viral proteins for replication, assembly of new viral particles) >

genetic material:

either DNA OR RNA

single/several nucleic acid molecules

nucleic acid molecules linear/circular

nucleic acid either ss/ds

may associate w/ nucleoproteins to form nucleocapsid

outer protein coat surrounding genetic material of virus >

capsid made up of capsomeres(individual protein subunits) >

function; protect, attach & introduce viral genome into host cells

derived from host CSM thru budding >

function; additional protective coat, gp spikes attach virus to specific surface receptor molecules on membranes of susceptible host cells,

alters recognition by host defense mechanisms