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BIO 210 > viruses > Flashcards

viruses Flashcards

1
Q

How does a bacteriaphage infect its host?

A

The protein capsid contains virus DNA or RNA and it this genome is injected into the cell of the bacteriophage (cell)

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2
Q

What is the most common way phages exit host bacterium?

A

cell lysis

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3
Q

Describe lysis - for phage exiting host bacterium

A

endolysin, is coded for in the viral nucleic acid of lytic phage

Endolysin attacks and breaks down bacteria’s cell wall peptidoglycan

Infected bacterium is destroyed as a result.

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4
Q

Describe basic steps of the lytic cycle of bacteriophage

A
  1. entry
  2. releases enzyme to break up host genome
  3. uses host genome to make it’s own material
  4. gets assembled
  5. enough are made lysis occurs
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5
Q

lysogenic cycle

A

ability of bacteriophage to integrate it’s genome into the host’s cell

  • some bacteria have the ability to take their genes and work them into the bacterial chromosome (red-blue double circle)
  • produces bacterial and viral DNA
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6
Q

what are viruses made of?

A

nucleic acid, proteins, and s/m lipids

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7
Q

describe a capsid of a virus

A

Nucleic acid surrounded by a protective protein coat, called a capsid.

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8
Q

describe envelope of a virus

A

Some viruses have an outer membranous layer, called an envelope, made of lipid and protein, surrounds the capsid in some viruses.

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9
Q

do all viruses have envelopes?

A

no

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10
Q

what is a difference between a naked and enveloped virus structure?

A

an enveloped has an envelope with spikes embedded into it (glycoproteins)

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11
Q

How do viruses differ from living organisms?

A

Viruses are not living organisms because they are incapable of carrying out all life processes

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12
Q

list characteristics of life that viruses do not conform to

A
  • are not made of cells
  • can not reproduce on their own
  • do not grow or undergo division
  • do not transform energy
  • lack machinery for protein synthesis
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13
Q

do viruses have more variety in nature of their genomes than do cells?

A

yes ; although much smaller than genomes of cells

can be dsDNA, ssDNA, dsRNA, and ssRNA

may be linear and composed of several segments or single and circular

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14
Q

the viral capsid function b/c it has a protein. coat

A

Protein coat provides protection for viral nucleic acid and means of attachment to host’s cells.

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15
Q

The viral capsid is composed of protein subunits called

A

capsomeres

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16
Q

capsids are composed of single type of capsomere while others are composed of multiple types; T or F

A

true

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17
Q

How is the viral enveloped acquired?

A

Acquired from host cell during viral release; envelope is portion of membrane system of host.

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18
Q

If the viral envelope is taken from an infected cell’s plasma membrane, what macromolecule is the viral envelope primarily made of?

A

Also contains proteins and virally-coded glycoproteins (spikes).

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19
Q

Envelope’s proteins and glycoproteins often play role in

A

host recognition

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20
Q

If a virus doesn’t have an envelope,it is considered to be a

A

naked virus

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21
Q

What is an advantage of having a cell envelope?

A
  • wouldn’t be picked up by immune cells (protection) invisible cloak
  • doesn’t require any work - just steals it (steals part of host for it’s own use)
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22
Q

How do viruses exit the cell?

A

lysis or budding

lysis = naked cell
budding = enveloped cell

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23
Q

How does a virus recognize & attach to its host?

A

Adsorption

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24
Q

Adsorption

A

The general phases in the life cycle of animal viruses are adsorption, *penetration, synthesis, assembly, and release from the host cell

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25
Q

why do most viruses infect only a certain type of host?

A

Specificity due to affinity of viral surface proteins to proteins on the surface of the host cell.

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26
Q

what characteristics bacteroiphages have that are attracted to proteins on the surface of bacterial cells?

A

bacteroiphages have proteins in their tail fibers (those extensions that look like legs)

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27
Q

What characteristics do animal viruses have that are attracted ot the glycoproteins on the surface of animal cells?

A

animal viruses have proteins or glycoprotein spikes that correspond to glycoproteins on the surface of animal cells.

28
Q

Virus exist outside and inside its host true or false

A

true

29
Q

what is the extracellular state called when a virus infects its host?

A

virion

30
Q

What is composed of the virion?

A
  • protein coat (capsid) surrounding nucleic acid
  • some have phospholipid envelope
31
Q

what is the outermost layer function for host cells?

A

Outermost layer provides protection and recognition sites for host cells

32
Q

How does a virus infects its host intracellular state?

A

capsid removed
virus exists as nucleic acid (genetic material)

33
Q

How does an animal virus infect its host? (2)

A
  1. Direct penetration of naked virus (Viral genome enters cell, while capsid remains on cell’s surface.)
  2. endocytosis
34
Q

what are three examples of animal virus entry?

A

influenza
herpes simplex virus
HIV/AIDS virus

35
Q

does viral genome have DNA, RNA, BOTH?

A

EITHER BOTH NEVER BOTH

36
Q

Pre-formed enzymes required for viral replication: polymerase function

A

DNA or RNA

37
Q

Pre-formed enzymes required for viral replication: Replicases

A

copy DNA

38
Q

Pre-formed enzymes required for viral replication: reverse transcriptase

A

synthesis of DNA from RNA

39
Q

When new animal viruses exit host cell it depends on what?

A

Depends whether or not they have an envelope.

40
Q

how do naked viruses exit the host cell?

A

After construction of capsid, naked viruses may be released from animal cell through exocytosis or may cause lysis and death of cell.

41
Q

how doe enveloped viruses exit the cell?

A
  • Often released through a process called budding
  • Virus exits cell with part of cell’s plasma membrane.
42
Q

Cytopathic effects

A

cell damage altering microscopic appearance

43
Q

what type of changes can cytopathetic effects cause?

A
  • Disorientation of individual cells
  • Gross changes in shape or size
  • Intracellular changes (inclusion bodies, syncytium)
44
Q

How long is latency of viruses? some can remain dormant

A

can remain for years with no (little) viral actiivty

45
Q

what do retroviral provirus do? ex. disease

A

Retroviral provirus incorporates into host DNA (HIV)

46
Q

Some latent viruses do not incorporate - name an example

A

herpes

47
Q

what type of virus is influenza?

A

RNA virus and segemented

48
Q

For influenza, where do viruses attach to and multipies?

A

respiratory tract

49
Q

How does influenza enter the nucleus?

A

segments of RNA genome enter the nucleus

50
Q

how does influenza assemble and leave the cell?

A

finished viruses are asembled and bud off the cell

INFLUENZA IS ENVELOPE

51
Q

RNA genome increases the risk of what

A

mutation

52
Q

What is key to influenza?

A

glycoprotein spikes like Hemagglutinin and Neuraminidase

53
Q

Hemagglutinin - how many subtypes?

A

15 subtypes

54
Q

Hemagglutinin function

A

binds to host cell; virulence factor (most important)

55
Q

Neuraminidase - how many subtypes?

A

9 subtypes

56
Q

Neuraminidase function

A

hydrolyzes mucus and assists viral budding and release

57
Q

Both glycoproteins, H and N, frequently undergo genetic changes, which decreases what?

A

the effectiveness of the host immune response

58
Q

Why makes influenza hard for memory cells to recognize?

A

high rate of mutation (RNA) - changes a lot —- akd antigentic drift

59
Q

antigenic drift

A

constant mutation – gradually change their amino acid composition

60
Q

antigenic shift

A

one of the genes or RNA strands is substituted with a gene or strand from another influenza virus from a different animal host

61
Q

what two things influence Influenza mutation?

A

antigenic drift

antigenic shift

62
Q

What is the most virulent influenza strand?

A

Influenza A

After 2003, strains of influenza A viruses that usually infect birds underwent an antigenic shift and began to infect humans

63
Q

what influenza strand undergoes antigenic drift but no antigenic shift?

A

Influenza B

64
Q

What influenza strand is known to only cause minor respiratory disease; probably not invovled in epidemics?

A

Influenza C

65
Q

Where does influenza A bind to?

A

Binds to ciliated cells of respiratory mucosa

Causes rapid shedding of cells, stripping the respiratory epithelium; severe inflammation

66
Q

symptoms of influenza A

A

Fever, headache, myalgia, pharyngeal pain, shortness of breath, coughing

BIO 210 (10 decks)

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