L35 - intro to virology Flashcards
outlines
- principles of virus structure and classification
- different stages and outcome of viruses
- life cycle of HIV
- basics of viral vaccines
properties of viruses
- obligate intracellular
- host specific
- one of the smallest biology entities (30-400nm)
- genome size varies from 3.2kb (4 genes) to 1.2Mb (911 genes)
what does it mean by viruses are obligate intracellular?
- can’t grow or replicate outside host (can’t live on their own)
- don’t acquire nutrients, produce energy or synthesise proteins
how are viruses classified?
- type of nucleic acid
- morphology
- presence/ absence envelope
- host organism
viral genomes of DNA viruses
- ssDNA
- dsDNA
viral genomes of RNA viruses
- single stranged
- double stranded
viral genomes of RNA <–> DNA viruses
- single stranded
- double stranded
structure of naked viruses
- no outer membrane e.g polio virus
- very simple
- shell of protein filled with nucleic acid
structure of enveloped viruses
- outer membrane
- derived from host cell membrane
- modified with viral proteins for recognition and attachment to host cells
stages of viral multiplication
- attachment
- entry and uncoating
- synthesis of viral components
- assembly
- release
attachment stage of viral multiplication
- viruses are not motile
- initial contact from random collision
- followed by specific interaction between attachment site on viral surface and receptor on cell surface
- SARS-Cov2 - ACE2 receptor on eptithelial cells
entry and unceasing stage of viral multiplication
- coupled process often
- entry through endocytosis (enveloped + naked virus)
- end-some formed and sent to lysosomes to dispose
- entry through fusion with membrane (enveloped)
- after entry of nucleic acid is prepared for expression/ replication: full or partial shedding of capsid proteins (uncoating)
synthesis of viral components stage of viral multiplication
- viral nucleic acid competes with host cell for control of biological machinery
- viral mRNA produced
- mRNA directs synthesis of early proteins
- these proteins direct nucleic acid replication
- synthesis of late proteins
assembly stage of viral multiplication
nucleic acid is either
1. packaged into preassembled capsid
2. associated with capsid proteins during formation
release stage of viral multiplication
- cytolysis: naked viruses
- budding: enveloped, developed derived from plasma memb
how are viruses released by cytolysis?
release by budding
- virus makes contact with memb
- memb wraps around virus
- piches off
- releases fully formed virus particle
- memb is modified with viral proteins
outcomes of viral infection
- cytocidal infection (acute infections that lead to lots of cells death)
- chronic infections (slow cell death)
- latent infection (infection has no symptoms for a while, something triggers it)
- transforming infections (cancers)