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biology topic 2 (cells and viruses) > viruses > Flashcards

viruses Flashcards

(54 cards)

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1
Q

how much times smaller are viruses than bacterium

A

50 times smaller

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2
Q

defenition of viruses

A

-not cells
-arrangemnts of genetic material and protein that invade other living cells and take over their biochemistry to make more viruses

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3
Q

obligate intracellular parasites

A

they can only exist and reproduce as parasites in the cells of other living organisms

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4
Q

envelope

A

coat around virus cell derived from lipids of host cell

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5
Q

capsid

A

protein coat is made up of simple repeating protein units

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6
Q

capsomeres

A

repeating protein units that make up capsids

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7
Q

benefits of using repeating units as capsomeres

A

-minimises the amount of genetic material needed to code for coat production
-makes protein coat simple as possible

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8
Q

benefits of having a lipid envelope

A

easier for viruses to pass from cell to cell

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9
Q

negatives of having a lipid envelope

A

vulnerable to substances such as ether which can dissolve lipid membrane

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10
Q

what are antigens also know as

A

virus attachment particles

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11
Q

how do viruses attach to host cells

A

by VAPs that target the cells surface memrbane

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12
Q

how are viruses classified

A

-by their genome and mode of replication

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13
Q

whats the genetic material in DNA viruses

A

DNA

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14
Q

what does the DNA do in DNA viruses

A

acts as template for new viral DNA and for mRNAs needed to induce synthesis of a viral protein

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15
Q

examples of DNA viruses

A

small pox
adenoviruses

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16
Q

examples of a bacteriophage

A

lambda phage

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17
Q

what are bacteriophages

A

viruses which infect bacteria

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18
Q

genetic material of RNA viruses

A

RNA

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19
Q

do DNA or RNA viruses mutate more

A

RNA

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20
Q

ssRNA

A

RNA viruses with a single strand of RNA

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21
Q

positive ssRNA

A

-positive sense RNA
-have RNA that can directly act as mRNA and be translated at the ribosomes

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22
Q

examples of plant and animal diseases caused by positive ssRNA

Study These Flashcards
A

tobacco mosaic virus
SARS
polio
hepatitis C

23
Q

negative ssRNA

Study These Flashcards
A

-negative sense RNA
-cant be directly translated

24
Q

what must happen to negative ssRNA before it can translate

Study These Flashcards
A

it must transcribe

25
examples of diseases caused by negative ssRNA
measeles influenza ebola
26
what do RNA retroviruses have structurally
lipid envelope and protein capsid
27
reverse transcriptase
enzyme synthesised in life cycle of retrovirus that makes DNA molecules corresponding to viral RNA genome
28
what happens to DNA made by reverse transcriptase
incooparated into the host cell DNA and used as a template for new viral proteins new RNA viral genome
29
example of retrovirus
HIV
30
how do bacteriophages infect host cell
inject genome into host cell but bulk of genome remains outside cell viral DNA forms capsid or plasmid around bacterium
31
endocytosis
host cell digests capsid revealing viral genome
32
most common way of virus entering host cells
viral envelope fuses with host cell surface releasing rest of viral genome
33
non virulent
what most viruses are when they first enter a cell dont causes disease
34
provirus
DNA injected into host cell
35
first step of lysogenic pathway
DNA inserted into host cell and is replicated every time host cell divides
36
why is mRNA not produced in lysogenic pathway
because of production of repressor protein that makes it impossible to translate rest of the viral genetic material
37
lysogeny
period when virus doesnt infect the host and make it ill
38
latent
state of non virulent virus in cell
39
what happens if viruses take the lytic pathway
the viral genetic material is replicated independently of the host DNA straight after entering the cell
40
how does lytic pathway effect host
lots of mature viruses made and host cell bursts damaged
41
virulent
viruses that cause illness
42
how does a virus in lysogenic enter lytic pathway
under certain conditions when host cell damaged amount of repressor protein decreased and viruses enter the lytic pathway and become virulent
43
what type of virus has lytic and lysogenic pathways
DNA viruses
44
lysis
when bacteria cell burst of lytic pathway
45
lysosome
enzyme produced when viruses replicate in lytic pathway and induce bacteria cells bursting
46
how to +ssRNA replicate
have sense strand that directly used as mRNA for translation into proteins at ribosomes
47
what proteins are made when positive ssRNA replicate
structural proteins RNA polymerase - replicates the viral RNA
48
how is negative ssRNA transcribed
virus imports RNA replicase which used free bases in host cell to transcribe antisense strand and produces a sense strand thats translated at ribosomes
49
what happens once RNA transcribed in -ssRNA
acts as mRNA at ribosomes and codes for viral proteins
50
role of negative ssRNA proteins produced
combine with replicated viral RNA to form new viral particles
51
how do retroviruses replicate
viral RNA transcribed into DNA by reverse trabscriptase in cytoplasm of cell viral DNA passes out of nucleus and inserted in host DNA host transcriptase enzymes make viral mRNA and new viral RNA genome -new particles released via exocytosis
52
why are viruses specific
because each cell has own markers and virus only bind to particular markers
53
how do antiviral drugs work
-target enzymes that aid in translation -inhibit protease enzymes that enable new particles to be produced -target receptors that recognize target cells
54

biology topic 2 (cells and viruses) (10 decks)

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