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Microbiology > Ch. 5 Viral structure and multiplication > Flashcards

Ch. 5 Viral structure and multiplication Flashcards

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Biology 101 flashcards
1
Q

What are the properties of Viruses?

A
  • Are obligate intracellular parasites of bacteria, protozoa, fungi, algae, plants, and animals
  • Do not independently fulfill the characteristics of life
  • Are ultramicroscopic in size
  • Are not cells; structure is very compact and economical
  • Basic structure consists of protein shell (capsid) surrounding nucleic acid core
  • can be either DNA or RNA but not both
  • need host to replicate
  • lack enzymes for most metabolic processes
  • lack machinery for synthesizing proteins
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2
Q

What are the components of a virus?

A
  • regular repeating subunits that give crystalline appearance
  • external coating
  • core containing DNA/RNA (one or more strands)
  • sometimes one or two enzymes
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3
Q

What is a capsid/nucleocapsid?

A
  • made from capsomeres
  • capsid is a protein shell that surrounds the nucleic acid
  • nucleocapsid - capsid together with the nucleic acid
  • naked virus are only nucleocapsid
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4
Q

What is an envelope?

A
  • external covering of a capsid, usually a modified piece of the host’s membrane
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5
Q

What are spike proteins?

A
  • project from the nucleocapsid or envelope
  • allows vires to dock with host cells
  • can be found in naked or enveloped viruses
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6
Q

What is a virion?

A

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

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7
Q

What are the different viral capsid shapes?

A
  1. helical - made from rod-shaped capsomeres
  2. Icosohedral - 3 dimensional, 20 sided, 12 corners; symmetrical
  3. Complex - may have multiple types of proteins. Not symmetrical, never enveloped, and only infects bacteria
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8
Q

Where can enveloped viruses bud from?

A
  • cell membrane
  • nuclear envelope
  • endoplasmic reticulum
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9
Q

What are the 2 different types of genomes for viruses?

A
  • DNA viruses - single-stranded or double-stranded (linear or circular)
  • RNA viruses - can be double-stranded; but more often single-stranded
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10
Q

What are the different types of viral RNA?

A
  • Positive-sense RNA - ready for immediate translation
  • Negative-sense RNA - must be converted before translation can occur
  • Segmented - individuals genes exist on separate pieces or RNA
    -Retroviruses- carry their own enzymes to create DNA out of their RNA
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11
Q

What are the enzymes in viral cells?

A
  • Polymerase - synthesize DNA and RNA
  • Replicase - copies RNA
  • Reverse transcriptase - synthesizes DNA from RNA
    no genes for synthesis of metabolic enzymes
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12
Q

What are the 5 general phases of viral replication?

A
  1. attachment
  2. Penetration/uncoating
  3. Synthesis
  4. Assembly
  5. Release
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13
Q

What is a host range?

A

The limited range of cells that a virus can infect
- cells that lack compatible virus receptors are resistant to adsorption and invasion by that virus

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14
Q

What is the attachment phase?

A

Where a virus invades its host cell only through making contact with a specific host molecule on its surface

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15
Q

What are tropsims?

A

specificities of viruses for certain tissues

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16
Q

What is the process of penetrating/uncoating?

A
  1. Flexible cell membrane of host is penetrated by either the whole virus or its nucleic acid
    - Penetration through endocytosis happens when an entire virus is engulfed
  2. Direct fusion of the viral envelope with the host cell membrane
    - envelope merges with cell membrane releasing nucleocapsid
17
Q

What is the difference in DNA v. RNA replications?

A

DNA viruses - enter host cell nucleus and are replicated and assembled there
RNA - replicated and assembled in the cytoplasm

18
Q

What is the assembly stage in viral replication?

A

virus is put together using the parts made during synthesis
* will overlap with synthesis

19
Q

What is the release stage in viral replication?

A
  • when the virus releases virions from the infected, usually by lysing the cell (naked) or budding (enveloped)
  • The number of viruses released by infected cells depend in size and health of host cell
20
Q

What is a bacteriophage?

A
  • means bacteria eating
  • viruses that infect bacteria
  • every bacterial species is parasitized by various specific bacteriophages
    most common in double-stranded DNA, but some RNA types exist
21
Q

What is the process of the lytic cycle?

A
  1. Phage injects its DNA into the cytoplasm of host
  2. Phage DNA directs the synthesis of many new phages
  3. cell lyses and releases the new phages
  4. New phages bind to other bacterial cells
    *only cycle for virulent phage
22
Q

What is the process of the lysogenic cycle?

A
  1. Phage injects its DNA into the cytoplasm of host
  2. Phage DNA integrates itself into the host cells genome
  3. Prophage DNA is then copied when the cell is divided, making multiple infected cells
  4. Exposure to stressors then triggers the excision from the host genome and moves to the lytic cycle
    *Temperate phages can do both the lysogenic and the lytic cycle
23
Q

What is an acute infection?

A
  • infection where virus lives in host cell for short periods
  • rapid multiplication leads to cell death and viral release always
  • like lytic cycle
24
Q

What is a latent infection?

A
  • infection of host cell where viral components are present in the genome, but the host is not immediately harmed
  • activation by stressors generally leads to activation and viral release/cell death
  • like lysogenic cycle
25
Q

What is a chronic infection?

A
  • infection of host cell leads to a slow release of virus without killing the host cell
26
Q

What is a transformative infection?

A
  • the viral genome disrupts the host cell cycle genes, which activates proto-oncogene (in humans) or insertion of oncogene (in animals)
  • leads to cancer
  • only type that disrupts host cell cycle genes
27
Q

Cytopathic effects (CPEs)

A
  • virus-induced damage to the cell that alters its microscopic appearance
28
Q

What are the types of CPEs?

A
  • gross changes in shape and size
  • Development of intracellular changes
  • inclusion bodies - compacted masses of viruses or damaged cell organelles in the nucleus and cytoplasm
  • syncytia - fusion of multiple damaged host cells into single large cells containing multiple nuclei
29
Q

What is transformation?

A
  • the effect of oncogenic viruses
30
Q

What are ways oncogenic viruses cause cancer?

A
  • some viruses carry genes that directly cause cancer
  • some disrupt cancer prevention genes
  • produce proteins that induce a loss of growth regulation
31
Q

What are the signs of transformed cells?

A

-increased rate of growth
- changes in their chromosomes
- changes in cell’s surface molecules
- capacity to divide indefinitely

32
Q

What are examples of oncoviruses?

A
  • Papillomaviruses
  • Herpes
  • Hepatitis B virus
33
Q

What are prions?

A
  • misfolded proteins
  • deposited as long protein fibrils in the brain tissue of humans and animals
  • exact mechanism of infection unknown

Microbiology (10 decks)

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