Lecture 2- Viruses Flashcards

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1
Q

what are viruses? how do they reproduce? multicellular or acellluar?

A

acellular infectious particles that are obligate intracellular pathogens (they reproduces only inside of living cells and they lack an independent metabolism)

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2
Q

what is a virus composed of? 3

A

nucleic acid genome (DNA or RNA)
capsid (protein coat)
some have an envelope

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3
Q

what do viral genomes consist of? (4)

A

DNA or RNA (never both but can flip from DNA outside the living organism then to RNA inside the organism and vice versa)
single stranded or double stranded
circular or linear
segmented (can be several pieces)

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4
Q

what is a virion?

A

encapsulated virus with DNA or RNA

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5
Q

what is the structure of a virion? what does it consist of? 2

A

capsid (protein coat that surrounds the genome)
envelope

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6
Q

what is a capsid made up of? what is their function

A

identical polypeptides (protomers)
in helical structures with nucleic acid genome is coiled inside
capsids allow for transfer of viral genome between host cells

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7
Q

what are two different kinds of capsids?

A

icosahedral capsid
binal capsid

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8
Q

what is a icosahedral capsid? how many sides does it have? what do the polypeptides do?

A

symmetrical geometrical shape with 20 triangular faces
protomers (polypeptides) aggregate to form capsomeres

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9
Q

what are binal capsids? what is the structure? what do the parts of the structure do?

A

geometric head with an attached helical tail
genome is in head, tail is used to inject DNA into a host cell

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10
Q

what is an envelope? what does it consist of?

A

a lipid bilayer surrounding the nucleocapsid that was acquired from the host membrane
consists of host lipids and spikes
ex. influenza virus has a flexible helical capsid surrounded by an envelope. has 2 major spikes hemaglutanin and neuraminidase

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11
Q

what do nucleocytoplasmic large DNA viruses have that other viruses dont?

A

multi- layered structure
some of these DNA viruses can be larger than bacteria

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12
Q

how does a virus infect a host?

A

attaches to specific receptors on the host cell surface
ex. HIV binds to CD4 receptor (only infects humans)

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13
Q

what is an example of a virus that infects more than one species?

A

influenza
binds to a glycoprotein on animal cells
thus infecting humans, pigs, chickens, seals…

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14
Q

what is a bacteriophage virus?

A

virus that infects bacteria

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15
Q

what is an animal virus?

A

virus infects and multiplys only inside animal cells

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16
Q

what is the goal of a virus?

A

to make more viruses

17
Q

how does the viral application cycle work? 5

A

1- absorption (attachment to the host cell
2- penetration and uncoating (entry into host cell)
3- synthesis of viral nucleic acids and protein
4- assembly of new virions
5- release of virions

18
Q

what are the two ways virions can get released?

A

naked virus: accumulate then lyse the host cell releases
enveloped virus: released by budding (virions push through the cytoplasmic membrane without killing the host cell)

19
Q

how exactly does a enveloped virus get released by budding?

A
  1. envelop proteins are inserted into host cells membrane
  2. viral matrix proteins bind the inner surface of the host cells membrane
  3. plasma membrane buds to form the viral envelope and release mature virion
20
Q

what are the two ways for a animal virus to enter a cell?

A

fusion with plasma membrane
endocytosis

21
Q

how does an animal virus use endocytosis to enter a cell?

A
  1. spikes bind to receptors
  2. virus gets surrounded (enveloped)
  3. capsid is removed and viral genome is released into the cell