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Z OLD Tissues of the Body > Viruses > Flashcards

Viruses Flashcards

1
Q

How big are viruses?

A

Submicroscopic- 18-350nm

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2
Q

What is required to see viruses?

A

An electron microscope

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3
Q

What is meant by viruses being obligate intracellular parasites?

A

They can’t independently replicate

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4
Q

Why are viruses obligate intracellular parasites?

A
  • They have no genes that encode proteins that function as metabolic machinery for energy generation
  • Can’t obtain molecules form which energy can be yielded
  • Have no genes that encode proteins that function as metabolic machinery for protein synthesis
  • May or may not contain genes that encode for enzymes involved in nucleic acid synthesis
  • May or may not have proteins processing nucleic acid
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5
Q

What is the significance of some viruses having proteins processing nucleic acids?

A

They can be used as targets for antiviral drugs

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6
Q

What is the genetic material in viruses?

A

DNA or RNA, not both

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7
Q

Which of the types of viruses, DNA or RNA, are more stable?

A

DNA

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8
Q

Why are DNA viruses more stable?

A

RNA is less genetically stable

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9
Q

What is the result of RNA being less genetically stable?

A

RNA viruses mutate faster than DNA viruses

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10
Q

Do viruses have small ions or polysaccharides?

A

No

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11
Q

Do viruses contain lipids?

A

Enveloped viruses do, naked viruses do not

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12
Q

What is the significance of naked viruses?

A

They are harder to destroy by heat or disinfectant

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13
Q

Give 4 viral shapes

A
  • Adenovirus
  • Papillomavirus
  • Parvovirus
  • Morbillovirus
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14
Q

Why are viral shapes important?

A

Because we can design drugs that directly fit the virus

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15
Q

Describe the growth curve of bacteria

A

Logarithmic, steady, exponential

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16
Q

Explain the growth curve of viruses

A

Low levels until the cell bursts, releasing a huge number of viruses

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17
Q

What are more difficult to control, bacterial or viral infections?

A

Viral

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18
Q

Why are viral infections more difficult to control than bacterial?

A

Because virus numbers are 3 orders of magnitude bigger

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19
Q

What is the genetic information for a virus?

A

Nucleic acid of RNA or DNA

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20
Q

Describe the genetic information for viruses

A

NAME?

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21
Q

What does segmented genetic information allow?

A

Reassortment, so can get lots of different strains

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22
Q

What can be if there is SS RNA?

A

Can be of plus or minus sense

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23
Q

What can happen if there is +RNA?

A

Genomic RNA can serve as mRNA, and so be directly translated into protein

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24
Q

Can genomic RNA serve as mRNA if it is of a - sense?

A

No

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25
Q

How is specific diagnosis of most viral infections achieved?

A

Molecular detection of their genomes

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26
Q

What is a long term survival strategy for viruses?

A

Converting RNA to DNA

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27
Q

What does the conversion of RNA to DNA require?

A

Reverse transcriptase

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28
Q

What is a virion?

A

A viral particle

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29
Q

Essentially, what is the envelope in an enveloped particle?

A

The host cytoplasmic membrane

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30
Q

What do all viruses have?

A

A nucleocapsid

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31
Q

What is the nucleocapsid?

A

A protein coat the encloses and protects the genomic material

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32
Q

How many protein types are in the nucleocapsid?

A

1, 2 or 3

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33
Q

What is true of the proteins that made up the nucleocapsid?

A

They are complementary units, and so stick together naturally

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34
Q

What are individual sub-units of nucleocapsids called?

A

Capsomeres

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35
Q

What is a nucleocapsid without a genome?

A

A capsid

36
Q

What are the functions of the capsid?

A
  • Protects delicate inner nucleic acid from harsh environmental conditions
  • May be involved in attachment to host cells
37
Q

What are the two basic capsid structures?

A
  • Icosahedral

- Helical

38
Q

What can capsomers be used to make?

A
  • Vaccines

- Antibodies to make diagnosis of viral infection

39
Q

What proteins to viruses encode for?

A

Ones that can naturally insert into host cell membrane

40
Q

What do the viral proteins inserted into the cell membrane allow?

A

The viral capsid to recognise part of the host membrane, which can then bud out to produce enveloped viruses

41
Q

What are the most numerous biological entities on the planet?

A

Bacteriophage T4-complex virus

42
Q

What are bacteriophage T4-complex viruses involved in?

A

Transfer of drug resistance

43
Q

How are bacteriophage T4-complex viruses involved in drug resistance?

A

They carry some of the proteins that enable bacteria to carry infection

44
Q

How do the viruses that infect human cells compare to those that infect bacteria?

A

Relatively similar

45
Q

What are the requirements for viral infection and replication in the host cells?

A
  • Cell must contain the receptor the virus binds to in the process of initiating infection
  • In order for virus to successfully replicate in host cells, the host cell must have cellular machinery the virus needs for replication
46
Q

Why can viruses only target specific cells/species?

A

Because the surface of the virus must come into contact with receptor in host cell, but the receptor might not be on all host cells

47
Q

What is the part of the virus that binds to the receptor called?

A

The ligand

48
Q

Where is the ligand found?

A

NAME?

49
Q

Is there a one ligand-one receptor relationship?

A

No

50
Q

What is the result of the possibility for multiple receptors for one ligand?

A

Complexities of some things that they cause

51
Q

What is the host range of a virus?

A

The spectrum of host cells that the virus can successfully infect and replicate in

52
Q

What is said if a virus successfully replicates in a host cell?

A

The infection is productive, and the host cell is permissive for virus

53
Q

What can sometimes happen when a cell produces viral particles?

A

The particles cannot infect new cells, which is an immunological advantage

54
Q

What is the most commonly used scheme for viral classification?

A

Baltimore scheme

55
Q

What is the Baltimore scheme based on?

A

Relationship between viral genome and the mRNA used for translation during expression of viral genome

56
Q

What do we use as the main classification in medical virology?

A

The nucleic acid type and envelope

57
Q

What are generally more susceptible to disinfection?

A

Enveloped viruses

58
Q

What are effects of a virus on the host cell?

A

Cytopathic effects, and cell death

59
Q

When does a virus usually cause cell death?

A

On release of the virus

60
Q

What are cytopathic effects?

A

Visible effects on the host cells caused by viral replication

61
Q

Give 4 cytopathic effects

A
  • Inclusion bodies
  • Syncytia formation
  • Chromosomal damage
  • Inhibition of host cell protein, RNA or DNA synthesis
62
Q

Where do inclusion bodies occur?

A

At the site of active virus synthesis

63
Q

Give an example of an inclusion body

A

Negri bodies in the rabies virus

64
Q

What are synctias?

A

Giant, multinucleated cells formed by the fusion of plasma membranes

65
Q

What causes chromosomal damage?

A

Viral nucleic acid can get into nucleus and integrate into host DNA

66
Q

What do many enveloped viruses produce regarding cytopathic effects?

A

No direct light microscope observable effects

67
Q

What does the development of cancer from viruses require?

A

That the virus integrates all of part of its genome into the host cell DNA

68
Q

What kind of viruses can cause cancer?

A

Only RNA viruses that are retroviruses

69
Q

How do RNA retroviruses cause cancer?

A

They bring in or turn on cellular oncogenes that cause cells to proliferate uncontrollably

70
Q

Can DNA viruses cause cancer?

A

Yes, but usually do so in a non-permissive cell

71
Q

What is meant by a non-permissive cell with regards to viral cancer?

A

A cell that lacks something required for viral growth

72
Q

How do DNA viruses usually cause cancer?

A

By inactivating tumour suppressor proteins that normally cat to keep the cell from going through the cell cycle, therefore the cell starts going through the cell cycle and proliferating

73
Q

What is a lot of what happens in infectious disease due to?

A

Overreaction of the immune system

74
Q

What are a lot of infectious disease treatments aimed at?

A

To stop the overreaction of the immune system

75
Q

What happens in people who are immunocompromised?

A
  • They don’t have the same symptoms as a normal person, so the diagnostic criteria must be changed
  • Will die much quicker because pathogen not being suppressed by immune system
76
Q

What happens in Ebola?

A

The virus both reduces the effective immune response, and enhances unproductive inflammation

77
Q

What do the complex interactions that occur in Ebola lead to?

A

Coagulation failure and the haemohagic picture

78
Q

What is the specific immune response to a disease often used as?

A

An alternative method of diagnosis to genome production

79
Q

What are the possible states of a virus?

A
  • Acute
  • Subacute
  • Chronic
  • Latent
80
Q

Where can viruses be obtained from?

A

NAME?

81
Q

What are the direct contact routes for viral infection?

A
  • Sexual contact
  • Vertical transmission
  • Environmental routes
  • Respiratory
  • Gastrointestinal
  • Transcutaneous
82
Q

What are viral infections characterised by?

A

Incubation period in which virus replication that eventually leads to damage/dysfunction that is symptomatic

83
Q

Where can a virus spread to?

A

NAME?

84
Q

How do many viruses spread?

A

Via multiple pathways

85
Q

How can viruses be detected?

A
  • Genome directed nucleic acid amplification (NAA)
  • Culturing in cell cultures
  • Identification of virus particles or antigens in tissue specimens
  • Detecting specific virus-directed immune response

Z OLD Tissues of the Body (19 decks)

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