4 - Viral properties Flashcards Preview

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Flashcards in 4 - Viral properties Deck (12):
1

What is meant by obligate?

cannot complete its lifestyle (replicate) without being inside a host cell
(uses the host cell machinery)

2

What are the characteristics of the non-enveloped virus morphology?

have a protein capsid and and symmetrical

3

What are the characteristics of the enveloped virus morphology?

- have proteins around their genome
- have a lipid envelope around them which is derived from the membrane of the host cell
- are PLEOMORPHIC - have lots of different shape

4

Which morphology does the Herpes virus have?

it is a combination of capsid and envelope

5

What are the features of RNA viruses and retroviruses?

- use own polymerises to replicate
- very error prone and lack proofreading capacity
- high mutation rate
- RNA virus genome is limited in size die the instability of its DNA

6

What are the features of DNA viruses?

- larger (since DNA is more stable)
- there is space for accessory genes
- genome can be one long strand or can be segmented e.g. influenza

7

Viral Replication:
What is the name of the protein on the surface of the virus that binds to the receptor on the host cell in the first stage?

viral attachment protein

8

Viral Replication:
What are the 2 ways that viruses enter the host cells?

- fusing with the host cell membrane and injecting the DNA/RNA genome into the cytoplasm
- enter via a series of vesicles such as endosomes

9

Give the generic virus replication cycle

- there is an inert virus on the outside
- its viral attachment protein binds to a receptor on the host cell surface (this docks down the virus onto the cell surface)
- virus enter the cell
- the viral genome is made into messenger RNA
- host ribosomes are used to translate the mRNA and make proteins
- at the same time, the genome is being replicated (either using viral or the host cells polymerases)
- the copies of the gnome and the viral proteins assemble to form new viral particles, which than leave the cell

10

Describe the replication cycle of influenza

- spike proteins are used to attach to the surface of the host cell
- it is engulfed and taken into an endosome
- it then fuses and releases its genome
- the genome enters the nucleus where it replicated and directs the synthesis of proteins
- they come other to form new virus particles

11

Describe the replication cycle of Ebola virus

- starts off as a worm like virus outside of the cell
- attaches to the cell receptor and is macropinocytosis
- in the early endosome it undergoes various cleavages, so it can interact with different receptors
- the genome is released and is copied into new genomes and into mRNA, to produce proteins
- proteins and genomes come assemble and bud out to form new virus particles

12

Describe the single step growth kinetics of a virus?

- the amount of virus at the start is know
- eclipse phase - no virus because all of it has gone into cells
- logarithmic increase - the virus makes new copies and exits the cells
- cell death - it tails off because cells start dying