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BIO1339 - Cell > Virus Cell Biology > Flashcards

Virus Cell Biology Flashcards

1
Q

What is a virus?

A

-DNA or RNA protected by a protein coat

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2
Q

What is the average size of a virus?

A

25-300 nm

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3
Q

What does a virus consist of?

A

RNA, DNA or both
Can be single or double stranded
5-200 poteins

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4
Q

What are extracellular forms of virus called?

A

Virion

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5
Q

What are virion?

A

Protein encapsulated DNA or RNA

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6
Q

What do virus infect?

A

Animals, plants, fungi and bacteria

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7
Q

Are virus alive?

A

No

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8
Q

Why are virus not alive?

A

Do not contain metabolic activity

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9
Q

What do you call virus particles?

A

Viroids

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10
Q

What are protein coats called?

A

Capsids

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11
Q

What proteins in the capsid called?

A

Capsomes

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12
Q

Do virus particles require help or self-assemble?

A

Self-assemble

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13
Q

What do capsids protects in virus?

A

RNA/DNA

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14
Q

What do capsids determine?

A

Shape of virus particle

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15
Q

What are the different organisations of virus particles?

A
  • Naked virus
  • Enveloped virus
  • Complex virus
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16
Q

Describe a naked virus:

A
  • Protein coat
  • Nucleic acid
  • Enzymes
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17
Q

What is an example of a naked virus?

A

Adenovirus

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18
Q

What does adenovirus cause?

A

cold, pneumonia, bronchitis

19
Q

Describe a enveloped virus:

A
  • Protein coat
  • Nucleic acid
  • Enzymes
  • Biomembrane (from host)
  • Enveloped protein (from virus)
20
Q

What is an example of an enveloped virus?

A

Human immunodeficiency virus (HIV)

21
Q

What does HIV cause?

A

acquired immunodeficiency syndrome (AIDs)

22
Q

Describe a complex virus:

A
  • Protein coat
  • Nucleic acid
  • Enzymes
  • Complex protein tail
23
Q

What is an example of complex virus?

A

T4 Phage

24
Q

What does T4 phage infect?

A

Bacteria

25
Q

What are the three distinct ways that virus particles enter the host cell?

A
  • Endocytosis
  • Membrane fusion
  • Injection
26
Q

How does the virus enter via endocytosis?

A

Virus triggers Cathrin-mediate endocytosis and enters the cell as a Trojan horse

27
Q

How does the virus enter via membrane fusion?

A

Enveloped virus particles bind to receptors in the plasma membrane of host and forces membrane fusion

28
Q

How does the virus enter via injection?

A

Bacteriophages infect their genetic information and leave the rest of the virus particle behind

29
Q

What are the two ways which a virus particle leaves the host cell?

A
  • Virus exocytosis

- Cell lysis

30
Q

How does a virus exit a host cell via viral exocytosis?

A

Virus particle assembles at the plasma membrane and “buds off”

31
Q

How does a virus exit a host cell via cell lysis?

A

Virus kills and disintegrates cell, releases the virus particles that are accumulating the cytoplasm

32
Q

What is it called when a virus is released from a host cell?

A

Virus egress

33
Q

What are bacteriophages?

A

Infecting bacteria and specialised to amplify themselves in bacteria

34
Q

What does bacteriophage T4 consist of?

A

25 structural proteins and double-stranded DNA (more than 134 genes)
Injection apparatis is contractile

35
Q

What is the life cycle of a bacteriophage?

A

Attachment:
-virus attaches to surface of bacterial cell
-Tail contracts, lytic enzyme breaks the cell wall and core needle pinches cell
Injection:
-Content of head (protein, DNA/RNA) released from cell
-Bacterial metabolism is disrupted and genomic DNA degraded
-Viral DNA transcribed into mRNA
-Viral DNA is replicated
-mRNA is translated into viral protein
Assembly:
-complex virus particle self-assemble
-50-100 phages assemble in the infected cell
Cell lysis and release:
-Lytic viral proteins (lysosome) disintegrates the cell and releases the phages

36
Q

What are different examples of enveloped viruses infect human?

A
  • Influenza virus
  • Coronavirus
  • HIV
  • Herpes simplex virus
  • Vaccinia virus
37
Q

Describe the entry of a virus of a host cell by fusion with plasma membrane:

A

Stage 1:
-Envelope via spike proteins interact with plasma membranes
-Spike proteins change confirmation - bringing virus particles close to plasma membrane until plasma membrane and viral envelope fuse
Stage 2:
-Opened up, the enveloped virus, releases content such as nucleic acids and potential enzymes where it can be amplified in the nucleus

38
Q

Describe the entry of a virus of a host cell by endocytosis:

A

Stage 1:
-Proteins in envelope trigger endoctyic uptake by acting as ligands for receptors
-Receptors then assemble a Cathrin coat forming around endocytic vesicles
-Clathrin coat disappeared leaving the endocytotic vesicle
Stage 2:
-Fusion of endosomal membrane and virus membrane release the DNA/RNA due to conformational changes by change in interior acidification

39
Q

How do viruses get their genetic material into the nucleus?

A

Virus particles use the intracellular transport machinery

40
Q

Describe the transport of virus genetic material into host nucleus:

A
  • Motors bind to virus-containing vesicle to move closer to nucleus by travelling across microtubules
  • Near nucleus, DNA released
  • Capsids can interact with motor proteins (directly interact)
41
Q

How do the virus particles move within infected cells?

A
  • Motility of virus particles depends on dynein
  • Move along microtubules and F-actin
  • Bi-directional motility at 2.5 micrometers per second
42
Q

Describe the assembly and exocytosis of enveloped viruses:

A
  • More DNA made, gets exported more readily new virus assembled
  • DNA transcribe, mRNA brought brought into cytoplasm for translation
  • Protein are made
  • Self-assemble to form a capsid
  • Capsid packed into new virus particles
  • Virus particles is then “budding-off” the plasma membrane
43
Q

Describe the order of the overview of the life cycle of an enveloped virus:

A
  • Binding
  • Endocytosis
  • Transport
  • Fusion
  • Transcription and Replication
  • Translation
  • Assembly
  • Budding
  • Release
44
Q

What is the tensile strength?

A

Force required to pull or push the capsid before it breaks

BIO1339 - Cell (9 decks)

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