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Micro Lecture > Viruses and prions > Flashcards

Viruses and prions Flashcards

1
Q

What aren’t viruses?

A

not living; they are acellular

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2
Q

What are viruses?

A

Small infectious particles
Obligatory intracellular parasites
Inert outside cells and hijack cell replication machinery

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3
Q

What do all viruses carry?

A

Genome (DNA or RNA)
Capsid (protein coat)

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4
Q

What are DNA and RNA viruses?

A

Double stranded and single stranded

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5
Q

What can viral protein coats contain?

A

Viral glycoproteins for cell entry

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6
Q

What are the building blocks of capsids?

A

Capsomeres

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7
Q

What surrounds some capsids?

A

Envelope

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8
Q

What is sent to the plasma membrane before a virus buds?

A

Viral glycoprotein

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9
Q

What happens when a virus has no envelope?

A

Glycoproteins are attached to the capsid

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10
Q

What is the new plasma membrane of a virus composed of?

A

Phospholipid bilayer

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11
Q

What is the envelope of a virus a combo of?

A

Glycoproteins and host cell molecules

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12
Q

What is a wide host range?

A

Multiple species are susceptible

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13
Q

What is a narrow host range?

A

Single species/cell in species are affected

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14
Q

What is the host range dictated by?

A

Lock and key recognition

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15
Q

What does the lock and key recognition mean?

A

Viral glycoproteins are keys that bind specific host cell surface receptors (locks)

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16
Q

What are the steps of viral replication?

A

Attachment
Entry
Synthesis
Assembly
Release

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17
Q

What does a virus focus on getting inside of a host cell?

A

Its viral genome

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18
Q

What is lytic replication?

A

Bacterial chromosome is destroyed to take away the competition

Same replication cycle

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19
Q

What is cell lysis?

A

In lytic replication- New phage is released- no envelope

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20
Q

What is the cycle of bacteriophages?

A

Attachment
Entry
Provirus
Replication of chromosome and virus- (cell division)
Further cell division
Induction
Synthesis
Assembly
Release

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21
Q

What is pro virus?

A

Step in lysogenic replication cycle in bacteriophage

Means that bacteriophage DNA is integrated into bacteria chromosome

Happens in animal viruses

22
Q

What are the mechanisms of virus entry?

A

Direct penetration
Endocytosis
Membrane fusion

23
Q

What are principles of direct penetration?

A

Can’t have an envelope
Capsid stays outside cell (what bacteriophage do)
Genome is injected into cell

24
Q

What is endocytosis?

A

Membrane of host reaches around and engulfs the virus

Virus is brought into an endosome

The virus is released from the endosome into the host cell cytoplasm

Can be enveloped or non-enveloped viruses

25
Q

What is membrane fusion?

A

Can only happen with enveloped viruses

Membrane is brought to the viral envelope and fuses

The viral glycoprotein stays at the surface

26
Q

What happens in a host cell when invaded by a DNA virus?

A

Viral genome is replicated by cell DNA polymerase in the nucleus

Host RNA polymerase transcribes DNA to RNA in the nucleus

Ribosome translates RNA into proteins in the cytoplasm

27
Q

What happens in a host cell when invaded by an RNA virus?

A

Virus needs special viral enzyme because genome does not match host cell’s

Viral genome is replicated by RNA polymerase in the cytoplasm

Ribosomes translate RNA into proteins in the cytoplasm

New viral genomes and proteins assemble in eukaryotes

28
Q

Where does DNA viruses assemble in host cells?

A

Nucleus

29
Q

Where do RNA viruses assemble in the host cell?

A

Cytoplasm

30
Q

How do non enveloped viruses leave host cells?

A

By lysis (plasma membrane ruptures)

31
Q

What is another way non-enveloped viruses sometimes leave host cells?

A

Exocytosis- vesicle with virus inside is transported to cell surface and fusion event allows virus to leave the cell

32
Q

How do enveloped viruses leave host cells?

A

Budding

33
Q

What are prions?

Where are the majority of them?

A

Misfolded normal cellular proteins

Majority in brain

34
Q

What can prions cause?

A

fatal Spongiform encephalopathies

35
Q

What are the 4 types of spongiform encephalopathies?

A

Scrapie (sheep), mad cow disease, kuru (New Guinea cannibals), Creutzfeldt-Jakob disease (spontaneous in humans)

36
Q

How are prions destroyed?

A

Incineration/autoclaving in concentrated sodium hydroxide

37
Q

How are prions transmitted?

A

Ingested
Transplantation
Contact mucous membranes with infected nervous tissue

38
Q

What is the incubation period for prions?

When does illness occur?

A

5 to 40 years

12 to 14 months before death

39
Q

How do prion diseases take over?

A

Infects brain cell & converts a normal protein into misfolded form

40
Q

What happens when prions build up?

A

Neuronal death occurs

Large vacuoles and plaques form; leads to death of the individual

41
Q

How many types of capsids are there?

A

4

42
Q

What do capsids do?

A

Protect genomes

43
Q

Where do DNA viruses assemble?

A

The nucleus

44
Q

Where do RNA viruses assemble?

A

Cytoplasm

45
Q

What is released when a virus is assembled?

A

Capsomeres and genome

46
Q

What is the cycle involved in silent replication called?

A

Lysogenic cycle

47
Q

What are the 2 methods non-enveloped viruses use to leave a cell?

A

Exocytosis and lysis

48
Q

How do non-enveloped viruses enter a cell?

A

Direct penetration and endocytosis

49
Q

What are the 2 methods enveloped viruses use to get inside of a cell?

A

Endocytosis and membrane fusion

50
Q

What step is unique to lytic replication of bacteriophage?

A

Bacterial chromosome is destroyed

Micro Lecture (7 decks)

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