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BIO 251 > Chapter 5: An Introduction to the Viruses > Flashcards

Chapter 5: An Introduction to the Viruses Flashcards

1
Q

Viruses are known to infect…

A

Every type of cell (bacteria, algae, fungi, protozoa, plants and animals)

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2
Q

Seawater can contain _____ viruses per milliliter

A

100 million

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3
Q

What did Louis Pasteur do in terms of viruses?

A
  • Postulated that a “living thing” smaller than bacteria caused these diseases
  • Also proposed the term virus
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4
Q

Virus is latin for..

A

Poison

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5
Q

20% of the human genome consists of sequences that come from…

A

Viruses

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6
Q

10-20% of DNA contains ______ _____

A

Viral sequences

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7
Q

Obligate intracellular parasites (meaning)

A

Cannot multiply unless they invade a specific host cell and instruct its genetic and metabolic machinery to make and release new viruses

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8
Q

Viruses are the _____ infectious agents known to man

A

Smallest

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9
Q

What are the smallest viruses called and how big are they?

A

Parvoviruses around 20 nm in diameter

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10
Q

What are the largest viruses and how big are they?

A

Mimiviruses around 450 nm in length

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11
Q

What is the newly discovered Pandoravirus?

A

Large virus nearly 1 um!

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12
Q

What are the largest human viruses?

A

Poxviruses

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13
Q

Some cylindrical viruses can be relatively long but are ______ in diameter

A

Narrow

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14
Q

Are viruses cells?

A

No, they lack any of the protein synthesizing machinery found in cells

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15
Q

What are the main parts that make up a virus?

A
  • External coating (capsid)
  • Core containing one or more nucleic acid strains of DNA or RNA
  • Sometimes one or two enzymes
  • Sometimes a membrane (envelope)
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16
Q

What can be contained in the “covering” of a virus particle?

A

Capsid

Envelope (not in all viruses)

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17
Q

What can be found in the “central core” of viruses?

A

Nucleic acid molecules

Matrix proteins Enzymes (not found in all viruses)

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18
Q

Capsids will be present in ___ viruses

A

All

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19
Q

Nucleic acids will be present in _____ viruses

A

All

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20
Q

Envelope of viruses

A

Usually a modified piece of the host’s cell membrane

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21
Q

What does a viral envelope determine?

A

Viral entry strategy

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22
Q

Capsid

A

Protein shell that surrounds a nucleic acid

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23
Q

Nucleocapsid

A

The capsid together with the nucleic acid

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24
Q

What are naked viruses?

A

Those without an envelope, consist only of a nucleocapsid

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25
Q

What is another name for spikes?

A

Peplomers

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26
Q

Spikes

A

Can be found on naked or enveloped virus, project from the nucleocapsid or the envelope and allow viruses to attach to host cells

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27
Q

Virion

A

A fully formed virus that is able to establish an infection in a host cell

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28
Q

Envelope is ______ of capsid

A

Outside

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29
Q

Is the viral envelope similar to the host’s membranes?

A

No, it differs significantly, some or all of the regular membrane proteins are replaced with viral proteins

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30
Q

What are viral glycoproteins?

A

They are exposed on the outside of the envelope

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31
Q

Enveloped viruses are ________

A

Pleomorphic

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32
Q

What does pleomorphic mean?

A

Have a variable shape ranging from spherical to filamentous

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33
Q

What does icosahedral mean?

A

20 equilateral triangles creating a spherical shape

34
Q

What does helical mean?

35
Q

What is the adenovirus?

A

An animal virus, icosahedral

36
Q

What is the bacteriophage structure like

A

Capsid head with tail sheath, pins, etc

37
Q

What shape does the Ebola virus have?

38
Q

What is the curled end of the Ebola virus called?

A

Shephard’s crook

39
Q

Can viruses contain DNA and RNA?

A

No, one or the other

40
Q

The number of viral genes is _____ compared to a eukaryotic cell

41
Q

Genome structure: DNA viruses can be: (4)

A
  • Single stranded
  • Double stranded
  • Linear
  • Circular
42
Q

Positive sense RNA

Single stranded

A

Ready for immediate translation, looks like mRNA

43
Q

Negative sense RNA

Single stranded

A

Must be copied before translation can occur (more resembles DNA)

44
Q

Can RNA viruses be segmented?

45
Q

Retroviruses

A

Carry their own enzymes to create DNA out of RNA

46
Q

Enzyme that makes DNA from RNA is..

A

Reverse transcriptase

47
Q

What is a common retrovirus?

48
Q

Influenza virus genomes have multiple strands of nucleic acid. The nucleotides ised to make the genome are A, U, G and C. This would be called a __________ virus.

A

Segmented RNA virus

49
Q

Polymerases

A

Synthesize DNA and RNA

50
Q

Replicases

51
Q

Do viruses have the genes for synthesis of metabolic enzymes?

A

No, they completely lack them

52
Q

Can viruses carry away substances from their host cell?

A

Yes, some can.. Retroviruses “borrow” the host’s tRNA molecules

53
Q

General steps of the animal viral replication cycle

A 
Absorption
Penetration
Uncoating
Synthesis
Assembly 
Release
54
Q

What happens during absorption?

A

Spike proteins attach to receptors on host cell

55
Q

What happens during penetration?

A

Receptor mediated endocytosis or membrane fusion

56
Q

What happens during uncoating?

A

Capsid proteins uncoat, releasing nucleic acids

57
Q

During / after uncoating, DNA viruses travel to…

58
Q

During / after uncoating, RNA viruses…

A

Remain in cytoplasm

59
Q

What happens during synthesis?

A

Protein synthesis-manufacturing virus components

Replication of the genome

60
Q

What happens during assembly?

A

All components of a vision assemble

61
Q

What is assembly like for icosahedral viruses?

A

Spontaneous

62
Q

What happens during release?

A

Budding or cell lysis

63
Q

What is budding?

A

Virus is pushed through cell membrane

64
Q

The length of the replication cycle varies from 8 hours in ______ to 36 hours in ______

A

Polioviruses

Herpesviruses

65
Q

What does the virus attach to on the host cell?

A

Glycoproteins usually

66
Q

How do non-enveloped viruses HAVE to enter the cell?

A

Receptor mediated endocytosis

67
Q

What happens during receptor mediated endocytosis?

A

Membrane of vesicle and virus fuse together

68
Q

What happens during membrane fusion?

A

Virus dumps viral core into cytosol

69
Q

Enveloped viruses exit cell by..

70
Q

Non-enveloped viruses exit by//

A

Lysing the cell

71
Q

Cytopathic Effects

A

Virus-induced damage to the cell that can alter its microscopic appearance

72
Q

Cytopathic Effects

A

Virus-induced damage to the cell that can alter its microscopic appearance

73
Q

Type of cytopathic effects

A

Gross changes in shape and size
Development of intracellular changes
Inclusion bodies
Synctia

74
Q

Inclusion bodies

A

Compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasm

75
Q

Synctia

A

Fusion of multiple host cells into single large cells containing multiple nuclei

76
Q

Viroids

A

Composed of naked strands of RNA, lacking a capsid or other type of coating

77
Q

What are viroids a significant concern for?

A

Economically important plants

78
Q

Prions

A

Composed entirely of protein

79
Q

What happens with prions?

A

Misfolded proteins cause other normal proteins to mis-fold

Contain no nucleic acid

80
Q

What kind of diseases are caused by prions?

A

Spongiform encephalopathies

BIO 251 (26 decks)

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