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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
What type of bacteria do T4 and Lambda infect?
E.Coli
26
Describe the virulence of T4 virus
Highly virulent
27
Describe the virulent of Lambda virus
Temperate
28
What is meant by a virus being temperate?
It does not immediately cause cell death
29
How many life cycles does the Lambda virus have?
2
30
What are the 2 life cycles of lambda?
Lytic and Lysogenic
31
What is the lytic life cycle of a virus ?
Infected bacteria are produced by Lambda bacteriophages and are lysed to release new bacteriophages
32
How do bacteriophages release new viruses in the lytic cycle?
By lysis of bacteriophage to release new bacteriophae
33
What is the lysogenic life cycle of a virus?
Bacteriophage genome is incorporated into bacterial host chromosome by genetic recombination that occurs at a specific site on the chromosome
34
By what process is a bacteriophage genome incorporated into a host cell genome in a lysogenic virus life cycle?
Genetic recombination
35
What is prophage?
The name for bacteriophage DNA when it is inserted into a bacteria host chromosome.
36
What is the name for bacteriophage DNA once it hast been inserted into a bacterial host chromosome?
Prophage
37
What type of cells does tobacco mosaic virus infect?
Plant cells
38
What type of structure does Tobacco mosaic virus have?
Helical symmetry and helical nucleocapsid
39
What type of viral nucleic acids does tobacco mosaic virus have?
RNA
40
Describe the most common shape of capsids in non-enveloped viruses.
Icosahedral
41
In non-enveloped, iscohedral capsids of viruses, how many capsid proteins are present?
Over 60
42
What are virus envelopes derived from?
Golgi membrane or nuclear membrane
43
How must viruses with envelopes be released fro a host cell?
They must or burst out of a host cell
44
Give examples of enveloped viruses
Measles | Influenza
45
Does influenza virus have an envelope?
Yes
46
How many main glycoprotein types does influenza virus have?
2
47
What are the 2 main types of Glycoproteins in influenza?
H- haemagglutin | N - neuraminidase
48
What is a retrovirus?
The DNA of the virus is converted to RNA by retrotranscriptase in the host cell.
49
What is used to classify influenza virus ?
The presence of different H and N proteins
50
What are the methods a virus can use to enter a host cell?
Direct penetration Membrane fusin Endocytosis
51
Outline the life cycle of an enveloped virus?
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
Do enveloped viruses kill host cells?
No
53
What part of a host cell is used to make viral glycoproteins?
Endoplasmic reticulum
54
What are the possible sites of virus assembly with a host cell
Golgi, nuclear membrane, cell membrane
55
Describe the nucleic acid presence in HIV
Single stranded RNA
56
What type of virus is HIV?
Retrovirus
57
What are the possible effects of viruses on host cells?
Cytopathic effects Transformation (tumour formation) Lysis (cell death) Persistent infection of cells Latent infection of cells
58
What is meant if a virus becomes latent?
It lays dormant in host cell
59
What are the types of viral cellular culture?
Primary cell culture Diploid cell lines Continuous cell lines
60
What type of tissue are primary viral cell cultures obtained from?
Live animal tissue
61
Describe the life span of a primary viral cell culture
Very limited
62
From what cell type are diploid viral cell cultures obtained from?
Homogenous cells from embryos
63
Describe the life span of diploid viral cell cultures
They divide about 100 times and then die
64
Describe the life span of continuous cell lines
They are immortal and don't stop growing
65
Where are continuous cell line cultures of viruses usually obtained from?
Cancerous cells
66
By what methods can viruses be quantified?
End point dilution assay Plaque assay
67
What method is used to isolate a single virus?
Plaque assay
68
Outline the process of forming a plaque assay of a single virus
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
Do plaques in a viral plaque assay show dead or live cells?
Dead

Microbial World (10 decks)

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