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Cells > Viral Cells > Flashcards

Viral Cells Flashcards

1
Q

Define the term ‘virus’.

A

DNA or RNA that is protected by a protein coat

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2
Q

Give the size range of a virus.

A

25-300nm

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3
Q

How many proteins can be found within a virus?

A

5-200

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4
Q

Name the extracellular form of a virus.

A

Virion

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5
Q

What is the name given to a virus that infects a fungus?

A

A Mycophage

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6
Q

How is the protein coat (capsid) of the virus made?

A

From a few proteins called ‘capsomers’ that self-assemble

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7
Q

What determines the shape of the virus?

A

The capsid

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8
Q

What structures are found in a naked virus?

A
  • A capsid/protein coat
  • Nucleic acid (RNA or DNA)
  • Enzymes
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9
Q

Give an example of a naked virus.

A

Adenovirus.

Causes colds, pneumonia, and bronchitis.

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10
Q

What structures are found in an enveloped virus?

A
  • A capsid/protein coat
  • Nucleic acid (RNA or DNA)
  • Enzymes
  • Biomembrane (lipids from the host cell)
  • Enveloped proteins
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11
Q

Give four examples of enveloped viruses.

A
  • HIV (Human Immunodeficiency Virus)
  • Influenza
  • Herpes Simplex Virus 1
  • Vaccinia virus
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12
Q

What structures are found in a complex virus?

A
  • A capsid/protein coat
  • Nucleic acid (RNA or DNA)
  • Enzymes
  • Complex protein tail
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13
Q

Give an example of a complex virus.

A

T4 Phage.

Infects bacteria.

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14
Q

Give the three ways that virus particles can enter host cells.

A
  • Endocytosis
  • Membrane fusion
  • Injection
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15
Q

Explain how a virus can enter a host cell by endocytosis.

A
  • The virus triggers Clathrin-mediated endocytosis

- Enters the cell as a “Trojan horse”

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16
Q

Explain how a virus can enter a host cell by membrane fusion.

A

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

17
Q

Explain how a virus can enter a host cell by injection.

A

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

18
Q

How many structural proteins make up the bacteriophage T4?

A

25

19
Q

What form of nucleic acid can be found in the bacteriophage T4?
How many genes?

A
  • Double-stranded DNA

- Over 134 genes

20
Q

Give the steps to the ‘lifecycle’ of T4 bacteriophage.

A
  1. The virus attaches to surface receptors.
  2. The tail contracts, lytic enzymes break the cell wall, and the core needle pinches the cell.
  3. The content of the head (proteins, DNA/RNA etc) is released into the cell.
  4. Bacterial metabolism is disrupted and the genomic DNA is degraded.
  5. Viral DNA is transcribed into mRNA.
  6. Viral DNA is replicated.
  7. Complex viruses self-assemble.
  8. Lytic viral proteins disintegrate the cell membrane and release the phages.
21
Q

How many T4 bacteriophages assemble in an infected cell?

A

50-100

22
Q

Explain how viruses can use the intracellular transport machinery.

A
  • Motors can bind directly to the viral capsid

- Motors can bind to a virus-containing vesicle

23
Q

What is required for virus replication?

A
  • Microtubules

- F-actin

24
Q

What causes the release of the viral DNA/RNA?

A

Fusion of the endosome and the viral membrane.

25
Q

What is the time taken for HIV assembly and release?

A

45 minutes

26
Q

Describe the release of droplets in a

a) cough
b) sneeze

A

a) cough = 3,000 droplets at up to 50mph

b) sneeze = 40,000 droplets at up to 100mph

27
Q

How many viruses are found per cubic metre of air?

A

16,000

28
Q

Give the steps to the life cycle of an enveloped virus.

A

1) entry by endocytosis or fusion of the viral lipid coat with the host plasma membrane
2) motor-driven transport towards the centre of the cell. where the nucleus is located
3) release of viral RNA or DNA and associated viral enzymes
4) replication of the genetic material
5) synthesis of coat and tail proteins
6) assembly of virions in the host cell
7) release of the virions by budding.

29
Q

What can bind to viral proteins to prevent conformational change?
How is this useful?

A

D-peptides.

Avoids fusion of viral membranes with the host.

Cells (18 decks)

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