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Biomolecular Mechanisms > Week 21: (A) Introduction to viruses > Flashcards

Week 21: (A) Introduction to viruses Flashcards

1
Q

What is a virus?

A

are not ‘alive’, but are obligate intracellular parasites that infect forms of life.

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2
Q

Why are viruses not alive?

A

they cannot encode all the things that you need to encode

e. g. no energy metabolism
e. g. no translational machinery

It is just a nucleic acid wound up in a protein shell

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3
Q

What is bacteria E.coli covered in?

A

bacteriophage T4

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4
Q

How do the bacteriophage T4 attack E.coli?

A

fibrils at the bottom of the syringe and attach on the cell surface
Once they attach they punch a hole in the bacterial cell wall and injects the viral DNA through that hole into the bacteria cell and the virus starts to replicate.

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5
Q

How does a virus replicate in a host cell?

A

proteins made using the bacteria translation machinery

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6
Q

Breakdown the structure of the bacteriophage T4?

A 
head region where the virus is enclosed
tail region (like a syringe)
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7
Q

What infection is common in bluegill fish?

A

lymphocytosis virus infection

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8
Q

How are viruses transferred to plants?

A

aphids, punch a hole and feed on the sap from the plant and inject plant with virus

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9
Q

What is the effect of viruses on plant?

A

Economic effect

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10
Q

What viruses infect insects?

A

Nuclear Polyhedrosis Virus

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11
Q

How do insects infect plants with virus?

A

GET TURNED INTO VIRUS FACTORIES
It turns squishy, full of virus
It will burst and spread all over surface of plant
virus is very resistant as it is encode in a shell so can survive on the plant for a number of years

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12
Q

What virus is abundant in live stock?

A

foot and mouth disease virus
lesion on cows tongue
lesion on pigs snout

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13
Q

What are the steps in the virus life cycle?

A
  1. recognition of host cell
  2. attachment (different for membrane bound and non-membrane bound viruses)
  3. penetration
    2’. attachment
    3’. fusion
  4. uncaring
  5. transcription
  6. protein synthesis
  7. replication
  8. assembly
  9. lysis and rues
    8’. envelopment
    9’. budding and release
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14
Q

What is an endosome?

A

membrane-bound vesicles, formed via a complex family of processes collectively known as endocytosis, and found in the cytoplasm of virtually every animal cell. The basic mechanism of endocytosis is the reverse of what occurs during exocytosis or cellular secretion.

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15
Q

What are the 2 easy in which virus can enter a host cell?

A
  1. non-membrane bound viruses by attachment and penetration

2. membrane viruses by attachment and fusion.

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16
Q

How does a virus with a membrane move into a cell?

A

The membrane of the virus contains viral proteins and bind to the membrane R o the host cell.
When it dies this it pull the membrane towards the virus and induces membrane fusion.
–> i.e fuse the membrane between the viral membrane and host membrane.
—–> effectively releasing the variant in t host cell’s cellular space.

17
Q

How does a virus with no membrane move int a cell?

A
  • Interact with the cell surf receptors of theist cell. (attachment)
  • The membrane evaginates around it, envelopes taken them entitle endosome.(penetration)
  • Within the endosome the virus has to escape.
  • Once it penetrates the cell it must release its genome into the cell. (uncoating)
18
Q

What happens after uncoating of a virus?

A

transcription and the generation of mRNAs .
mRNAs are translated on cellular ribosome to make protein.
The protein can either continue to replicate the genome.

19
Q

What is the late phase of replication?

A

Makes lots of replications of the capsid proteins

20
Q

What do capsid proteins do?

A

they assemble around the viral genomes and make new viral particles

21
Q

What the faits of the new viral particles?

non-membrane an membrane…

A

1) non membrane viruses- undergo assembly and lysis and release

2) membrane viruses- viruses that are going to be enveloped are going to assemble near the membrane, insert viral proteins into the cell membrane
Eventually buds and is released.

22
Q

What does a viral growth curve show?

A

the virus life cycle

23
Q

What is the s first phase in the virus growth curve?

A

latent period

24
Q

What is the latent period of the virus growth curve?

A

there is a decrease in the infectious units per cell.

virus a been uncoated and is non-infectious

25
Q

How many viral particles can a single virus make?

A

10e5 can go and escape and infect other cells.

26
Q

What are some simple forms of virions?

A
  • Naked isosahedral capsid
  • Enveloped icosahedral
  • Naked helical nucleocapsid
  • Enveloped helical nucleocapsid
27
Q

What types symmetry is there in a icosahedral Capsid?

A

5- fold symmetry of proteins

6-fold symmetry

28
Q

What is an icosahedral capsid?

A

the building block for symmetrical viruses

29
Q

What is used to determine the properties of a virus?

A

taxonomic constructions

30
Q

What are the taxonomic constructions?

A

b) Properties of genome
1. Type of nucleic acid - DNA or RNA
2. strandedness- single or double stranded
3. linear or circular
4. sense: positive, makes RNA infectious, Negative, naked RNA non-infectious and needs an enzyme to copy RNA
5. number of segments
6. nucleotide sequence

31
Q

What is a negative strand?

A

Opposite senesce form mRNA

if you put that into a cell its non-infectious

32
Q

How does a virus overcome a negative strand?

A

The virus has to bring in a transcriptase that will copy the negative strand into a positive strand
Have to cope the negative strand into a positive strand
–>The RNA found in a negative-sense virus is not infectious by itself, as it needs to be transcribed into positive-sense RNA.

33
Q

What are types of viruses DNA molecules?

A 
linear single strand 
circular single stranded 
linear duple 
duplex with closed ends
closed circular duplexes (with and without supercoils)
34
Q

What are the types of virus RNA molecules?

A
  • Linear, single strand infectious, “positive” (+) strand
  • linear, single strand non-infectious, “negative” (-) strand
  • segmented positive strands
  • segmented negative strands
  • double strand segmented
  • diploid single strands
35
Q

What are the benefits of a positive RNA strand?

A

it an be directly translated by the translation machinery

36
Q

What are the largest viruses?

A

pox viruses
double stranded DNA
ds DNA

37
Q

What are the smallest viruses?

A

parvo-viridae
ss DNA
single stranded DNSA ~700 bases

Biomolecular Mechanisms (34 decks)

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