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BIO111: Microbiology > Chapter 13 > Flashcards

Chapter 13 Flashcards

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1
Q

Virus Characteristics

A
  • Obligate intracellular parasitic molecules
  • non-motile
  • non-living
  • over 6,000 known to man
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2
Q

Structure of Viruses

A
  • DNA or RNA
  • linear or circular
  • single or double stranded
  • code for enzymes like DNA or RNA polymerase and enzymes to make rest of virus particle
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3
Q

Cell Structure

Virus

A

do not have organelles or ribosomes

-only protein and nucleic acids

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4
Q

Metabolism

virus

A

require host for synthesis of nucleic acid and proteins

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5
Q

Nucleic acids

virus

A

contain DNA or RNA, either single or double stranded

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6
Q

Genes

virus

A

have 4- 200 genes

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7
Q

bacteria # of genes

A

3000

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8
Q

humans have ____ genes

A

30,000

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9
Q

Size

virus

A

viruses are 100-1000x smaller than cells

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10
Q

Capsid

A
  • found in all viruses
  • made of protein subunits called CAPSOMERES
  • carries enzymes needed for infection
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11
Q

Common virus shapes

A

Icosahedral
Helical
Complex

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12
Q

Icosahedral

A

20 sided polygon

20 triangles, 12 corners

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13
Q

Helical

A

rod-shaped capsid

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14
Q

Complex

shape

A

ex. T4 phage: icosahedral head and tail of helical arranged proteins

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15
Q

Envelope

A

lipid bilayer outside of capsule

- only in some viruses

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16
Q

Naked viruses

A

lack envelope, most phages

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17
Q

Enveloped viruses

A

envelope surrounds capsid

  • disinfectants damage envelope making virus non-infectious
  • matrix proteins found between envelope and capsid, give different shapes to virus
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18
Q

Spikes

A
  • protein structures that allow virus to attach to host
  • on capsid, envelope, or tail
  • virus subtype based on spikes
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19
Q

purpose of capsid and envelope

A

protect the nucleic acid from enzymes and toxic chemicals

ex. polio virus - naked virus can survive GI tract

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20
Q

purpose of spikes and capsid

A

allow virus to attach to host cell

capsid has special proteins for naked cells to help it attach

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21
Q

Classification and Naming of Viruses

A
  • not classified as a kingdom or domain because not living
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22
Q

Two superfamilies

A

DNA or RNA

human viruses 7 DNA families, 13 RNA families

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23
Q

Family names end in

A

-viridae

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24
Q

Genus names end in

A

-virus

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25
Q

Enteric viruses

A

transmitted by fecal- oral route

ex. polio

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26
Q

Zoonotic viruses

A

transmitted to humans by animals

ex. rabies, cow pox

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27
Q

Arboviruses

A

arthropod borne viruses

ex. west nile

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28
Q

bacteriophages

A

viruses that infect bacteria

AKA phages

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29
Q

Characteristics used in classification

A
  • Genome structure
  • type of host
  • shape of capsid
  • overall size
  • presence of cell envelope
  • how virus affects host cell
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30
Q

Potential relationship of virus with host

A
  1. Productive state

2. Latent or Lysogenic State

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31
Q

Productive state types

A

Lytic

Chronic

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32
Q

Latent or Lysogenic state types

A 
Latent = animal cells
Lysogenic = bacteria cells
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33
Q

Lytic

A

Productive
Host cell is destroyed by lysis when new viruses released
ex. HIV and lymphocytes

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34
Q

Chronic

A

Host cell survives and continues to divide while releasing viruses
ex. HIV and macrophage

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35
Q

Productive Lytic - Bacteriophage

T4 virus

A

T4 = double stranded DNA viruse, infects E.coli

  1. Attachment/Adsorption
  2. Penetration/ Genome entry
  3. Synthesis
  4. Assembly
  5. Release
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36
Q

Attachment/Adsorption

A
  • viruses non-motile so they collide with host by chance

- infection depend on specific receptor sites on outside of host cell

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37
Q

Where are receptor sites located on bacteria and animal cells

A

bacteria - cell wall, flagella and pili

animal cell - cell membrane

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38
Q

type of organisms of cell types that virus can infect, usually very specific

A

Host range

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39
Q

Penetration/Genome Entry

bacteria

A
  • viral nucleic acids enter host cell
  • enzyme lysozyme from tip of T4 virus tail digest part of E.coli cell wall.
  • Tail contracts and phage DNA injected through cell wall and cell membrane to cytoplasm
  • capsid remains outside of host cell
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40
Q

Synthesis

bacteria

A

Synthesis and transcription of viral DNA and production of new viral parts
- uses machinery of host cell (ribosomes, some enzymes) to make “phage-encoded” proteins

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41
Q

types of “phage-encoded” proteins

A

Early proteins

late proteins

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42
Q

Early proteins

A

nuclease that destroys host cell DNA, proteins that modify host RNA polymerase - so no host proteins are made

43
Q

Late proteins

A

structural proteins to make capsid and tail

44
Q

Assembly

bacteria

A
  • virus particles assembled into mature viruses
  • some parts assemble spontaneously
  • other parts require extra enzymes and proteins for assembly
45
Q

Release

Bacteria

A
  • mature viruses are released
  • phage-encoded LYSOZYME starts digestion of cell wall from inside
  • osmotic pressure causes cell to lyse break
  • viruses are expelled
46
Q

Burst size

A

number of phages released

about 200 for T4 viruses

47
Q

Attachment/adsoption

Animal

A
  • Virus recognizes and attaches to host
  • Spikes on virus bind to specific receptor sites on host membrane
  • in animals, often are two different receptros proteins
  • receptors usually have a different purpose for the host
    ex. rabies attaches to Acth receptor of nerve cells
48
Q

Penetration/uncoating

animal

A
  • in animals the whole virus enters the host cell (in bacteria just the nucleic acid enters)
  • Two methods:
    Endocytosis and fusion
49
Q

Endocytosis

A
  • whole virus is moved into cell by endocytosis
  • virus is engulfed in a vesicle made by host
  • occurs with naked and enveloped viruses
  • uncoating- host enzymes dissolve capsid and envelope and nucleic acids are released
50
Q

Fusion

A
  • Viral envelop fuses with host cell membrane
  • only capsid and genome enter host
  • uncoating occurs to release nucleic acid
51
Q

Steps of animal productive lytic

A
  1. Attachment (adsorption)
  2. Penetration (genome entry) (uncoating)
  3. Synthesis -> nuclease (breaks down nucleic acids)
  4. Assembly
  5. Release (budding) enveloped viruses
52
Q

Synthesis

A
  • Synthesis and transcription of viral nucleic acid and production of new viral parts using machinery of host cell just as in phages
  • genome is expressed and copied
  • viral enzymes made
  • capsomeres and spikes made
53
Q

Synthesis DNA viruses

A

Double stranded - “normal” mechanisms

Single stranded - made into double stranded before transcription

54
Q

Synthesis RNA viruses

A

Single and Double stranded - viral enzyme REPLICASE (RNA polymerase) makes new RNA for new viruses, replicases do not proof-read like DNA polymerase which explains mutations of influenza virus

55
Q

Synthesis (Revers Transcriptase)

A
  • Some viruses have complex system of genome sythesis
    ex. RETROVIRUSES (including HIV)
  • Viral RNA is made into DNA using viral encoded enxyme called REVERSE TRANSCRIPTASE
  • this double stranded DNA is incorporated into host DNA
  • Virus can become productive or latent
56
Q

Assembly

animal

A
  • virus particles assembled into mature viruses

- if the virus is enveloped, then spikes are placed within the cell membrane of the cell

57
Q

Release

animal

A

Mature viruses are released

  • human virus burst size = 3,000 - 50,000 viruses/one cell
  • enveloped vs. Naked viruses
58
Q

Enveloped Viruses

Release- Animal

A
  • Budding
  • viruses released slowly, host cell usually not destroyed
  • Host cell can be damaged
59
Q

Budding

A

vesicle (from cell membrane or Golgi) surrounds virus, spikes added to membrane

60
Q

Ways host cell can be damaged in release of enveloped viruses

A
  • Shutdown of metabolism and genetic expression
  • Destruction of cell or organelle membranes
  • toxicity of viral components
61
Q

Naked virus - release

Animal

A
  • Cell fills with viruses
  • spontaneously lyses
  • Release can be caused by virus triggering normal host immune responses
  • host cell death
62
Q

Productive Chronic Bacteriophage

A
  • M13 filamentous, single stranded DNA phage

- virus released without killing host cell

63
Q

4 steps of Productive Chronic Bacteriophage

A
  1. Attachment
  2. Penetration
  3. Synthesis
  4. Assembly
64
Q

Attachement

Bacteriophage

A

attaches to F pilus

65
Q

Penetration

Bacteriophage

A

injects DNA through pilus to cytoplasm

66
Q

Synthesis

Bacteriophage

A

Host DNA polymerase used to synthesize viral DNA, capsomeres put into bacteria membrane

67
Q

Assembly

Bacteriophage

A

capsomeres surround the viral DNA as it exits

68
Q

Viral Relationships with Host Cells

Latent/Lysogenic

A
  • No new viruses are produced by host cell
  • Viral nucleic acid incorporated into host chromosome
    - incorporated viral DNA called prophage in bacteria and provirus in animal cells.
  • Host cell continues to divide and viral DNA is replicated with each new cell made
69
Q

Lysogenic or Latent… what cell type and name

A

Lysogenic - Bacteria called prophage

Latent - Animal cell called provirus

70
Q

most viral genes are NOT expressed in ______ state

A

lysogenic/latent

if genes are expressed the living host cell can produce new types of proteins- gives host new characteristics

71
Q

Viral repressor proteins

A

can prevent production of the hosts excision proteins

72
Q

excision proteins

A

found on host cell that cut viral DNA out of host chromosome

73
Q

induction

A

excision proteins allowed to cut and release viral DNA, virus goes from lysogenic to productive/lytic

74
Q

temperate virus

A

AKA lambda phage

a virus that can go from lysogenic to productive lytic

75
Q

if the bacteriophage is inside it is in what phase

A

lysogenic phase

76
Q

types of human viruses

A

virulent
latent
temperate

77
Q

virulent viruses

A

always productive lytic, rapid, severe, destructive, cell death but not always organism death,
Ex. Influenza, mumps, polio

78
Q

latent viruses

A

non-active, in dormant state inside cell, incorporate DNA into host chromosome
ex. HIV and herpes

79
Q

Temperate viruses

A

can cause lysis or become latenet, environmental conditions may influence which state is present
ex. herpes

80
Q

Acute infections

A

-cause disease symptoms for short periods of time
- body can develop life-long immunity
- viruses are productive
- extensive tissue damage and cell death, but is usually localized
- much of damage can be repaired after recovery
Ex. mumps, measles, influenza, cold virus

81
Q

Persistent infections

A
  • specific virus is present in host for long periods of time, life-long possible
  • virus can be productive or latent depending on state of disease
  • disease symptoms may not be apparent
  • host become carrier of infective viruses
82
Q

Late complications following acute infection

persistent

A

relapse can occur years after recovery from an acute infection
Ex. measles and subacute sclerosing panencephalitis (SSPE)

83
Q

latent infections

persistent

A

similar infection occurs days to years after recovery from acute infection, viruses are not detected until disease onset.

  • Herpes family viruses - shingles, chicken pox, genital herpes, cold sores
  • Herpes simplex 1 - cold sores in mouth, move to neurons when latent, environmental triggers cause movement of virus back to mouth
84
Q

Chronic infections

persistant

A

continuous production of low levels of viruses often in absence of disease symptoms
ex. Hep B and C - acute phase includes nausea and fever, virus can persist and slowly cause liver cirrhosis

85
Q

Slow infections

persistant

A

number or viruses slowly increases over a long period of time
ex. HIV/AIDS

86
Q

Cancer

A

abnormal condition of unregulated cell division

87
Q

Tumor

A

mass of abnormally dividing cells

88
Q

Benign tumor

A

remains within a localized region

89
Q

Malignant tumor

A

cells migrate (metastasize) to other location

90
Q

Regulatory genes

A

can regulate rate and frequency of cell division - without regulation cell may become cancerous

91
Q

Two types of regulatory genes

A

Proto-oncogenes

Tumor-suppressor genes

92
Q

proto-oncogenes

A

activate transcription, increase rate of cell division, cancer develops if gene is always on

93
Q

tumor- suppressor genes

A

stop cell division, cancer develops if gene is turned off

94
Q

Regulatory genes are altered by

A

Mutation - 80% of cancer (50% on tumor-suppressors, 30% on proto-oncogenes)
Viruses - 15% (or more) of all human cancers
last 5% is d/t genetic predispositon

95
Q

Oncoviruses general info

A
  • viruses that can transform host cell into a cancer cell
  • latent - viral genes incorporated into host DNA
  • induction can be caused by decreased immunity, stress, fever, UV exposure
96
Q

Oncovirus definition

A

disrupt and permanently turn on proto-oncogenes

97
Q

Retrovirus

A

RNA viruses use revese transcriptase to make double stranded DNA which is incorporated into host DNA, can modify host cell function including conversion to cancer cell

98
Q

viroids

A
  • single stranded, circular RNA, no capsid
  • no proteins produced
  • infect only plants
  • mechanisms of disease production unknown
    ex. potato spindle tuber
99
Q

prions

A
  • compose only of proteins
  • affect CNS of humans and other animals
  • Scrapie in sheep, Bovine spongegiform encephalophathy, and Creutzefeld-Jakob disease in humans
  • very stable - resistant to heat and chemicals
    Mechanisms unknown - normal host proteins destroyed, nerve cells destroyed.
100
Q

Person infected with HIV virus by symptoms are not present

A

HIV infection

101
Q

person infected with HIV and symptoms ARE present

A

HIV disease

102
Q

Last stage of HIV disease, characterized by opportunistic infections

A

AIDS

Aquired Immunodeficiency Syndrome

103
Q

Causative Agent of HIV

A

single stranded RNA virus, enveloped, retrovirus.

HIV-1 is more common in US than HIV-2

BIO111: Microbiology (12 decks)

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