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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
What is another name for spikes?
Peplomers
26
Spikes
Can be found on naked or enveloped virus, project from the nucleocapsid or the envelope and allow viruses to attach to host cells
27
Virion
A fully formed virus that is able to establish an infection in a host cell
28
Envelope is ______ of capsid
Outside
29
Is the viral envelope similar to the host's membranes?
No, it differs significantly, some or all of the regular membrane proteins are replaced with viral proteins
30
What are viral glycoproteins?
They are exposed on the outside of the envelope
31
Enveloped viruses are ________
Pleomorphic
32
What does pleomorphic mean?
Have a variable shape ranging from spherical to filamentous
33
What does icosahedral mean?
20 equilateral triangles creating a spherical shape
34
What does helical mean?
Spiral?
35
What is the adenovirus?
An animal virus, icosahedral
36
What is the bacteriophage structure like
Capsid head with tail sheath, pins, etc
37
What shape does the Ebola virus have?
Irregular
38
What is the curled end of the Ebola virus called?
Shephard's crook
39
Can viruses contain DNA and RNA?
No, one or the other
40
The number of viral genes is _____ compared to a eukaryotic cell
Small
41
Genome structure: DNA viruses can be: (4)
- Single stranded - Double stranded - Linear - Circular
42
Positive sense RNA | Single stranded
Ready for immediate translation, looks like mRNA
43
Negative sense RNA | Single stranded
Must be copied before translation can occur (more resembles DNA)
44
Can RNA viruses be segmented?
Yes!
45
Retroviruses
Carry their own enzymes to create DNA out of RNA
46
Enzyme that makes DNA from RNA is..
Reverse transcriptase
47
What is a common retrovirus?
HIV
48
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.
Segmented RNA virus
49
Polymerases
Synthesize DNA and RNA
50
Replicases
Copy RNA
51
Do viruses have the genes for synthesis of metabolic enzymes?
No, they completely lack them
52
Can viruses carry away substances from their host cell?
Yes, some can.. Retroviruses "borrow" the host's tRNA molecules
53
General steps of the animal viral replication cycle
``` Absorption Penetration Uncoating Synthesis Assembly Release ```
54
What happens during absorption?
Spike proteins attach to receptors on host cell
55
What happens during penetration?
Receptor mediated endocytosis or membrane fusion
56
What happens during uncoating?
Capsid proteins uncoat, releasing nucleic acids
57
During / after uncoating, DNA viruses travel to...
Nucleus
58
During / after uncoating, RNA viruses...
Remain in cytoplasm
59
What happens during synthesis?
Protein synthesis-manufacturing virus components | Replication of the genome
60
What happens during assembly?
All components of a vision assemble
61
What is assembly like for icosahedral viruses?
Spontaneous
62
What happens during release?
Budding or cell lysis
63
What is budding?
Virus is pushed through cell membrane
64
The length of the replication cycle varies from 8 hours in ______ to 36 hours in ______
Polioviruses | Herpesviruses
65
What does the virus attach to on the host cell?
Glycoproteins usually
66
How do non-enveloped viruses HAVE to enter the cell?
Receptor mediated endocytosis
67
What happens during receptor mediated endocytosis?
Membrane of vesicle and virus fuse together
68
What happens during membrane fusion?
Virus dumps viral core into cytosol
69
Enveloped viruses exit cell by..
Budding
70
Non-enveloped viruses exit by//
Lysing the cell
71
Cytopathic Effects
Virus-induced damage to the cell that can alter its microscopic appearance
72
Cytopathic Effects
Virus-induced damage to the cell that can alter its microscopic appearance
73
Type of cytopathic effects
Gross changes in shape and size Development of intracellular changes Inclusion bodies Synctia
74
Inclusion bodies
Compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasm
75
Synctia
Fusion of multiple host cells into single large cells containing multiple nuclei
76
Viroids
Composed of naked strands of RNA, lacking a capsid or other type of coating
77
What are viroids a significant concern for?
Economically important plants
78
Prions
Composed entirely of protein
79
What happens with prions?
Misfolded proteins cause other normal proteins to mis-fold | Contain no nucleic acid
80
What kind of diseases are caused by prions?
Spongiform encephalopathies

BIO 251 (26 decks)

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