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Microbial World > Week 5 > Flashcards

Week 5 Flashcards

1
Q

Describe the relative size of viruses to other miroorganisms

A

Smallest

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2
Q

What is meant by viruses being infectious, obligate, intracellular parasites?

A

They cannot complete their life cycle without exploiting a host cell.

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3
Q

What do viruses require a host cell for?

A

To carry out genome replication and synthesis of viral compartments.

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4
Q

By what means are viruses within host cells transmitted to the next host cell?

A

Progeny virions

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5
Q

What are progeny visions?

A

They bud from one cell and allow spread of infection from one cell to another (used by viruses).

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6
Q

What do host cells provide to viruses and what is each component used for?

A

Nucleotides for nucleic acid production.

Ribosomes and amino acids for translation of proteins.

ATP for energy

Gold and endoplasmic reticulum for protein processing

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7
Q

What type of nucleic acids can viruses have?

A

DNA or RNA

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8
Q

What are the possible capsid structures of viruses?

A

Helical
Icosahedral
Complex

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9
Q

What are viruses without the presence of an envelope known as?

A

Naked

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10
Q

Describe the structure of a viral nucleocapsid .

A

Viral nucleocapsids are highly symmetrical and are composed of one protein capsid which is formed by the specific arrangement of capsomers.

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11
Q

How is the capsid of a virus formed?

A

By the specific self-assembly of capsomers.

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12
Q

Do viruses metabolise?

A

No

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13
Q

Do viruses respond to the environment?

A

No

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14
Q

What type of host cells do bacteriophage viruses infections?

A

Bacterial cells

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15
Q

Describe the virulence of bacteriophage infections

A

Highly virulent

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16
Q

What is the virulence of an organism?

A

The severity of harmfulness and ability of an organism to cause disease.

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17
Q

Is the structure of bacteriophages simple or complex?

A

Complex

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18
Q

Outline the features which are present in the structure of a bacteriophage.

A

Head, collar tail, tail pins, tail fibres

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19
Q

How are different bacteriophages classified?

A

By their shape and nucleic acids

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20
Q

What are the stages of bacteriophage life cycle?

A

Attachment

Penetration

Synthesis of nucleic acids and proteins

Assembly and Packaging

Release / lysis

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21
Q

Outline how bacteriophages undergo attachment to host cells.

A

All viruses have attachment proteins on their outside. This protein attaches to specific receptors on host cell surfaces. These viruses are normal proteins found on the outside of host cells

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22
Q

Where are the proteins that recognise host cells found in bacteriophages?

A

In the tail fibres

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23
Q

What do viral components mature to in the host cell?

A

Virons

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24
Q

What are Virons?

A

An entire virus particle consisting of a capsid and nucleic acid capsule.

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25
Q

What type of bacteria do T4 and Lambda infect?

A

E.Coli

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26
Q

Describe the virulence of T4 virus

A

Highly virulent

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27
Q

Describe the virulent of Lambda virus

A

Temperate

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28
Q

What is meant by a virus being temperate?

A

It does not immediately cause cell death

29
Q

How many life cycles does the Lambda virus have?

A

2

30
Q

What are the 2 life cycles of lambda?

A

Lytic and Lysogenic

31
Q

What is the lytic life cycle of a virus ?

A

Infected bacteria are produced by Lambda bacteriophages and are lysed to release new bacteriophages

32
Q

How do bacteriophages release new viruses in the lytic cycle?

A

By lysis of bacteriophage to release new bacteriophae

33
Q

What is the lysogenic life cycle of a virus?

A

Bacteriophage genome is incorporated into bacterial host chromosome by genetic recombination that occurs at a specific site on the chromosome

34
Q

By what process is a bacteriophage genome incorporated into a host cell genome in a lysogenic virus life cycle?

A

Genetic recombination

35
Q

What is prophage?

A

The name for bacteriophage DNA when it is inserted into a bacteria host chromosome.

36
Q

What is the name for bacteriophage DNA once it hast been inserted into a bacterial host chromosome?

A

Prophage

37
Q

What type of cells does tobacco mosaic virus infect?

A

Plant cells

38
Q

What type of structure does Tobacco mosaic virus have?

A

Helical symmetry and helical nucleocapsid

39
Q

What type of viral nucleic acids does tobacco mosaic virus have?

A

RNA

40
Q

Describe the most common shape of capsids in non-enveloped viruses.

A

Icosahedral

41
Q

In non-enveloped, iscohedral capsids of viruses, how many capsid proteins are present?

A

Over 60

42
Q

What are virus envelopes derived from?

A

Golgi membrane or nuclear membrane

43
Q

How must viruses with envelopes be released fro a host cell?

A

They must or burst out of a host cell

44
Q

Give examples of enveloped viruses

A

Measles

Influenza

45
Q

Does influenza virus have an envelope?

A

Yes

46
Q

How many main glycoprotein types does influenza virus have?

A

2

47
Q

What are the 2 main types of Glycoproteins in influenza?

A

H- haemagglutin

N - neuraminidase

48
Q

What is a retrovirus?

A

The DNA of the virus is converted to RNA by retrotranscriptase in the host cell.

49
Q

What is used to classify influenza virus ?

A

The presence of different H and N proteins

50
Q

What are the methods a virus can use to enter a host cell?

A

Direct penetration
Membrane fusin
Endocytosis

51
Q

Outline the life cycle of an enveloped virus?

A

The envelope of the lipid bilayer of the virus has glycoprotein spices which fuse with the cell membrane of the hose cell.

The host cell is then used to synthesise a viral nucleic acid genome and viral proteins.

Endoplasmic reticulum of the host cell is used to make viral glycoproteins.

Progeny viruses bud from the cell and allow the cell membrane to kill the cell

52
Q

Do enveloped viruses kill host cells?

A

No

53
Q

What part of a host cell is used to make viral glycoproteins?

A

Endoplasmic reticulum

54
Q

What are the possible sites of virus assembly with a host cell

A

Golgi, nuclear membrane, cell membrane

55
Q

Describe the nucleic acid presence in HIV

A

Single stranded RNA

56
Q

What type of virus is HIV?

A

Retrovirus

57
Q

What are the possible effects of viruses on host cells?

A

Cytopathic effects

Transformation (tumour formation)

Lysis (cell death)

Persistent infection of cells

Latent infection of cells

58
Q

What is meant if a virus becomes latent?

A

It lays dormant in host cell

59
Q

What are the types of viral cellular culture?

A

Primary cell culture
Diploid cell lines
Continuous cell lines

60
Q

What type of tissue are primary viral cell cultures obtained from?

A

Live animal tissue

61
Q

Describe the life span of a primary viral cell culture

A

Very limited

62
Q

From what cell type are diploid viral cell cultures obtained from?

A

Homogenous cells from embryos

63
Q

Describe the life span of diploid viral cell cultures

A

They divide about 100 times and then die

64
Q

Describe the life span of continuous cell lines

A

They are immortal and don’t stop growing

65
Q

Where are continuous cell line cultures of viruses usually obtained from?

A

Cancerous cells

66
Q

By what methods can viruses be quantified?

A

End point dilution assay

Plaque assay

67
Q

What method is used to isolate a single virus?

A

Plaque assay

68
Q

Outline the process of forming a plaque assay of a single virus

A

Virus innoculated on a monolayer of cells or bacteria.

Overlayer of agar added
(Virus can only spread cell to cell)

Holes or plates of dead cells form in the monolayer

69
Q

Do plaques in a viral plaque assay show dead or live cells?

A

Dead

Microbial World (10 decks)

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