13 - Viruses Flashcards
Name and describe the 2 parts of viruses that ALL viruses have
- nucleic acid (DNA or RNA; single or double; linear or circular)
- capsid
What is the 3rd part that SOME viruses have but not all?
envelope (lipid bi-layer; looks similar to plasma membrane; usually an envelope comes with spikes)
Capsid
protein coat, 1+ types protein - different arrangements and capsomere subunits - determines shape of virus
What are the 3 shapes of viruses?
- helical (long rod, rigid/flexible) - rabies/Ebola
- polyhedral (many sides) - polio/cold
- complex (complex structures) - bacteriophages
What virus part determines its shape?
capsid
What can we use to grow viruses in a lab?
have to use a host
for example bacteriophages need to be grown inside bacteria
What are the different methods for growing animal viruses in the lab?
- living animals
- embryonated eggs
- cell cultures
Steps of the bacteriophage replication cycle
- attachment
- penetration
- biosynthesis
- maturation
- release
Lytic cycle of bacteriophage
host cell dies (host cell lyses to release viruses)
Lysogenic cycle of bacteriophage
host cell survives (virus integrates into host chromosome)
Animal virus multiplication:
attachment -> entry -> uncoating -> biosynthesis -> maturation -> release
Attachment of the animal virus replication cycle
- envelope viruses use spikes
- non-envelope viruses uses corners of the capsid
How do viruses achieve ENTRY into an animal cell?
receptor-mediated endocytosis (plasma membrane folds in, vesicles) - the envelope is left behind at the host cell membrane
What is being uncoated when a virus enters an animal cell?
the coat is being degraded - the nucleic acid is separated from protein coat
What two parts does the virus need to make in an animal cell for biosynthesis?
- nucleic acid
- capsid protein
Biosynthesis for DNA viruses:
- DNA -> RNA -> protein (capsid)
- DNA -> DNA (nucleic acid)
Biosynthesis for RNA viruses:
- RNA -> complimentary RNA -> original RNA (nucleic acid)
- RNA -> protein (capsid)
Biosynthesis for retroviruses
- RNA -> DNA
- DNA integrates into host DNA
- DNA -> RNA -> protein
What allows for retroviruses to convert RNA to DNA?
reverse transcriptase
When a virus enters an animal cell, what happens during maturation?
assembly of all the parts made in biosynthesis
How does release occur after maturation has been completed?
- envelope: buds releasing of virus into envelope
- non-enveloped: rupture of plasma membrane releases viruses
Oncogenes
genes that can cause cancer when over-activated (normally turned off after birth)
Tumor suppressor genes
genes that control unregulated cell growth (normally turned on)
Oncogenic viruses
induce tumors, 10% cancers are virus related - genes within the virus lead to uncontrollable cell division or interfere with tumor suppressor/oncogenes (i.e. HPV/EBV)
Latent viral infection
virus remains integrated in the host genome (herpes, chickenpox) - will become activated by weak immune system, stress, etc.
Persistent viral infection
effects of virus infection occurs gradually over long period
Acute viral infection
short-term (lots of virions at once)
