describe structural components of viruses
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
describe structural components of enveloped virus, influenza
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
describe structural components of enveloped virus, HIV
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
describe structural components of T4 bacteriophage
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
describe structural components of lambda bacteriophage
icosahedral capsid, encloses linear dsDNA molecule >
tail sheath only 1 tail fibre
describe structure of viral genome
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
describe function of capsid
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
describe function of viral envelope
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