Introduction to virology Flashcards
What structures are featured in simple viruses (5)
Envelope coat with glycoproteins
Envelop
Capsomeres
Viral nucleic acid genome
Matrix
What structures are features in complex viruses (6)
Nucleic acid genome
Capsid
Tail sheath
Plate
Pins
Tail fibres
What is the process of virus reproduction (7)
Attachment
Entry
Transcription
Translation
Genome replication
Assembly
Exit
What happens during viral attachment
binding between virus structures cell surface receptors through hydrogen bonds, ionic attractions and van der Waals forces drawing the virus closer to fuse with the membrane.
What happens during viral entry (2)
When bound to receptors on the host cell the virus is brought closer to the cell surface where it fuses with the cell membrane
Naked viruses bind to the receptors and endocytosis occurs where the cell membrane bends and the virus is engulfed inside. When inside the cell a membrane is formed around the virus within the cell.
What happens during viral transcription
double stranded and single stranded DNA are transcribed by host enzymes whereas double stranded and single stranded RNA are transcibed by enzymes brought in by the virus. With the exception of ss(+)RNA(retroviruses) which is reverse transcribed into DNA using the virus enzymes to be transcribed by the host cell enzymes.
What happens during viral translation
performed using host cell ribosomes translating messenger RNA into proteins. Generating proteins for viral (ORF) assembly and packaging within viron (enzymes). May be more that one open reading frame to save space on viral genome meaning the same sequence of nucleotides can synthesise multiple proteins by shifting the codon triplets by one.
What happens during viral genome replication
when occurs in the cytoplasm its usually RNA. When occurs in the nucleus its usually DNA.
What happens during viral assembly
Simple virons may self-assemble whereas larger virons are assembled using scaffolding proteins.
What happens during viral exit (2)
With enveloped virions, the virus capsid is directed to modify the membrane and buds off the cell surface taking some of the modified cell membrane as an envelope. The cell is left intact.
Other virons form their own membrane and other virons leave the cell through lysis of the host cell.
What are phages (3)
Phages are also known as bacteriophages they are a special type of virus which only infect bacteria.
Most commonly found in the gut with the gut bacteria.
It can be grown on an agar plate containing bacteria.
What are tailed phages (2)
A phage where the capsid is icosahedral and the tail is helical.
They force their way into the host by injecting nucleic acid through the cell wall.
What are the main uses of viruses (5)
- Phage typing of bacteria (e.g. Salmonella spp.)
- Sources of enzymes
- Pest control
- Antibacterials - phage therapy to lyse bacteria.
- Gene therapy
What are prions (2)
Prions are infectious proteins which induce the conversion of alpha-helix in PrPc (A) [a copper transport protein] to beta-sheets of PrPc (B).
Prions form vacuoles and hardened plaques of prion protein in the brain leading to brain damage.
How are prions decontaminated (4)
Incineration if possible
Immerse in sodium hydroxide and autoclave at 121℃ for 30 mins; clean and autoclave again.
Autoclave at 134℃ for 18 mins
Flood surfaces with 2N NaOH or undiluted sodium hypochlorite; let stand for 1hr; mop up and rinse with water.
