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Microbiology Final > Chapter 5: Viruses > Flashcards

Chapter 5: Viruses Flashcards

1
Q

Seawater can contain ______ viruses per mL

A

100 million viruses per mL

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2
Q

Louis Pasteur

A

Postulated that a “living thing” smaller than bacteria was causing certain diseases; also proposed term “virus” (latin for poison)

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3
Q

Living characteristics of viruses (2)

A
  1. They reproduce at a fantastic rate, but only in living host cells;
  2. They can mutate
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4
Q

Non-living characteristics of viruses (2)

A
  1. They are acellular,
    1. that is, they contain no cytoplasm or cellular organelles;
  2. They carry out no metabolism on their own and must replicate using the host cell’s metabolic machinery.
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5
Q

Parvoviruses

A

smallest viruses; 20 nm in diameter

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6
Q

Mimiviruses

A

largest viruses; 450 nm in length

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7
Q

Virus particles contain __________ DNA or RNA

A

either; not both

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8
Q

Viral Components (3)

A
  1. Nucelic Acid
  2. Capsid
  3. Envelope
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9
Q

Capside

A

protein shell that surrounds the nucleic acid

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10
Q

Nucleocapsid

A

the capsid together with the nucleic acid; naked viruses consist only of this

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11
Q

Envelope

A

external covering of a nucleocapsid; usually a modified piece of the host’s cell membrane

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12
Q

Spikes

A

allow viruses to dock with host cell; can be found on BOTH naked and enveloped viruses

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13
Q

Virion

A

a fully formed virus able to establish an infection in the host cell

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14
Q

Capsomeres/Protomers

A

identical protein subunits that make up the capsid

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15
Q

Enveloped Virus

A

a virion with an envelope (most viruses that infect animals are enveloped)

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16
Q

Naked Virus

A

a virion without an envelope

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17
Q

How do envelopes form?

A

When viral glycoproteins and oligosaccharides associate with the cell membrane of the host cell

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18
Q

All envelopes have a _________

A

Phospholipid bilayer

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19
Q

Genome packaging plays an important role in ________

A

the infection

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20
Q

3 ways genomes are packaged:

A
  1. Directly in the capsid-inner side of the protein coat;
  2. Enclosed in special proteins-nucleic acid binding protein;
  3. Enclosed in proteins from the host cell
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21
Q

Variola Virus

A

small pox; double-stranded DNA

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22
Q

Herpes Simplex II

A

Herpes; double-stranded DNA

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23
Q

Parvovirus

A

Erythema Infectiosum; single-stranded DNA

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24
Q

Poliovirus

A
  • Poliomyelitis;
  • Single-stranded RNA;
  • (+) polarity
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25
Q

Influenza Virus

A
  • Influenza;
  • Single-stranded RNA;
  • (-) polarity
26
Q

Rotavirus

A
  • Gastroenteritis;
  • Double-stranded RNA
27
Q

HIV

A
  • AIDS;
  • Single-stranded RNA reverse transcriptase
28
Q

Tobacco Mosaic Virus (describe shape)

A

hollow tubes with protein walls

29
Q

Influenza Virus (describe shape)

A

an enveloped virus with a helical nucleocapsid

30
Q

Icosahedral Viruses (describe shape)

A

derived from 20 triangular vases that make up the capsid; has 12 points of symmetry

31
Q

Polymerases

A

synthesize DNA or RNA

32
Q

Replicases

A

copy RNA

33
Q

Reverse transcriptase

A

synthesizes DNA from RNA

34
Q

Lytic Infection

A

the host cell fills with virions and explodes; result is cell death

35
Q

Lysogenic (Latent) Infection

A

the viral genome becomes incorporated into the host cell’s DNA; can remain this way for an extended period; results in host cell living

36
Q

6 steps in lytic cycle:

A
  1. adsorption
  2. penetration
  3. uncoating
  4. synthesis
  5. assembly
  6. release

A Pony Undergoes Some Awesome Racing

37
Q

Length of replication cycle in Polioviruses

A

8 hours

38
Q

Length of replication cycle in Herpesviruses

A

36 hours

39
Q

Adsorption

A

A virus can invade its host cell only through making an exact fit with a specific host molecule/Receptor sites/Specific surface structures on host to which viruses attach. These can be proteins, lipopolysaccharides, teichoic acids, etc.

40
Q

Penetration

A

The flexible cell membrane of the host is penetrated by the whole virus or its nucleic acid

41
Q

Penetration through endocytosis

A

entire virus is engulfed by the cell and enclosed in a vacuole or vesicle

42
Q

Uncoating

A

(1) enzymes in the vacuole dissolve the envelope and capsid; (2) virus fuses with the wall of the vesicle; (3) viral nucleic acid is released into the cytoplasm

43
Q

Direct Fusion

A

occurs with influenza and mumps viruses; (1) envelope merges directly with the cell membrane; (2) nucleocapsid is released to the cell’s interior

44
Q

DNA Virus Synthesis:

A

replicated and assembled in the nucleus

45
Q

RNA Virus Synthesis:

A

replicated and assembled in the cytoplasm

46
Q

Retrovirus Synthesis:

A

Once inside the host cell cytoplasm the virus uses its own reverse transcriptase enzyme to produce DNA from its RNA genome, the reverse of the usual pattern

47
Q

Retrovirus

A

a single-stranded RNA virus that stores its nucleic acid in the form of an mRNA genome and targets a host cell as an obligate parasite

48
Q

Assembly

A

puts together the new viruses using the “parts” manufactured in the synthesis process: new capsids and new nucleic acids

49
Q

The number of viruses released by infected cells is controlled by these 2 factors

A

(1) Virus size; (2) Health of the host cell

50
Q

Poxvirus releases ___ virions

A

3,000-4,000

51
Q

Poliovirus releases ___ virions

A

100,000

52
Q

Oncogenic Virus

A

Virus capable of initiating tumors; 20% of cancers are caused by these

53
Q

Transformation

A

effect on the cell caused by oncogenic viruses; (1) increased rate of growth; (2) alterations in chromosomes; (3) changes in the cell’s surface molecules; (4) capacity to divide for an indefinite period

54
Q

2 ways viruses cause cancer

A
  1. virus carries genes that directly cause cancer
  2. virus produces proteins that induce a loss of growth regulation in the cell
55
Q

2 cancer-causing viruses

A
  1. papillomaviruses (cervical cancer)
  2. Epstein-Barr virus (lymphoma)
56
Q

Bacteriophage

A

Virus that infects bacteria; often make the bacteria more pathogenic

57
Q

Parts of Bacteriophage (7)

A
  1. icosahedral capsid head
  2. central tube
  3. collar
  4. base plate
  5. tail pins
  6. fibers
58
Q

Prions

A

an infectious protein, specifically a protein in a misfolded form; a common feature of spongiform encephalopathies;

59
Q

Creutzfeldt-Jacob disease

A

infects the human nervous system; causes gradual degeneration and death; prions

60
Q

Bovine spongiform encephalopathy (BSE)

A

contracted when consuming contaminated beef; infected develop a variant of Creutzfeldt-Jacob disease

61
Q

Viroids

A

Virus-like agents that parasitize plants; 1/10 the size of viruses; naked strands of RNA (lack capsids)

62
Q

Interferon

A

naturally occurs in human cells to stop virus replication; is used with some success in treating and preventing viral infections

Microbiology Final (12 decks)

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