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Rachel Microbiology > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

True/ False: Viruses are obligate

A

True

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2
Q

Viruses are: Intracellular/ Extracellular

A

Intracellular

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3
Q

True/ False: Viruses are parasites

A

True

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4
Q

Obligate

A

Forced to

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5
Q

Intracellular

A

Inside the cell

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6
Q

Parasites

A

Depend on other organisms for their food

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7
Q

What does a virus need to be able to multiply?

A

Viruses can’t multiple unless they 1) invade a specific host cell, and 2) instruct its genetic and metabolic machinery to make and release new viruses

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8
Q

How big is a virus?

A

Very small, 20-400nm

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9
Q

True/ False: Viruses are acellular

A

True

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10
Q

How many viruses are known? How many cause human disease?

A

About 5000 known, about 220 cause human disease

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11
Q

Virology

A

The study of viruses

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12
Q

Bacteriophages

A

Viruses that infect bacteria

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13
Q

Animal viruses

A

Viruses that infect animals and humans

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14
Q

Smallest viruses

A

Rhinoviruses and polioviruses, diameter as small as 30 nm

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15
Q

Biggest viruses

A

Ebola and pandora viruses, lengths nearing 1000 nm. Pithovirus is one of the largest, length of 1,500 nm

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16
Q

Sub microscopic

A

Can’t be seen with a compound microscope (like viruses)

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17
Q

What does it mean that viruses aren’t filterable

A

Membrane filters that trap bacteria are not enough to trap viruses

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18
Q

Virion

A

Single virus particle that is capable of infecting another cell

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19
Q

What is something that all visions must have?

A

Nucleocapsid

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20
Q

Nucleocapsid is made of what two components

A

Capsid and nucleic acid

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21
Q

Capsid

A

Protein layer that covers and protects

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22
Q

Nucleic Acid

A

RNA or DNA (virus can have one or the other, not both)

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23
Q

Features that a virion might have (not necessary)

A

Envelope and spikes

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24
Q

Envelope

A

Lipid membrane covering outside the capsid

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25
Q

Spikes

A

Proteins on the outside of the capsid/ envelope

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26
Q

Virus particle is covered by BLANK (always) and may sometimes also have BLANK

A

Capsid always, may also have envelope

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27
Q

Viral core has BLANK (always) and may also have BLANK

A

Always has nucleic acid (DNA or RNA), sometimes has matrix protein enzymes

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28
Q

Capsid

A

Protein shell that packages and protects the genome. This is most of the visions mass. Made of capsomere subunits

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29
Q

Capsomere

A

subunits of a capsid

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30
Q

Shape of the BLANK determines the shape of the virus

A

Capsid

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31
Q

What are some different capsid shapes

A

helical, icosahedral, complex

32
Q

Helical

A

cylindrical, like a hollow tube

33
Q

Icosahedral

A

20 sided structure, 3D polygon

34
Q

Complex capsid shape

A

Often seen in bacteriophages, has a polyhedral head, tail, and sheath for injection

35
Q

Enveloped viruses

A

Have a lipid-based envelope that surrounds the capsid

36
Q

How do envelopes arise?

A

Budding off the host cell (they take a piece of the cell membrane with them)

37
Q

Naked

A

No envelope

38
Q

How do naked viruses arise?

A

Lysing (bursting) the host cell

39
Q

Are animal viruses naked, enveloped, or both?

A

Could be either

40
Q

Are bacteriophages naked, enveloped, or both?

41
Q

Glycoprotein

A

Proteins modified with sugars that extend from the capsid or envelope

42
Q

What do glycoprotein spikes do?

A

Help virus attach to host cells and infect

43
Q

Examples of influenza spike proteins

A

Neuraminidase (NA) and Hemagglutinin (HA), frequently mutated by small changes

44
Q

How many genes in the viral genome?

A

Usually small, only about 300 genes

45
Q

What 3 things does viral genome carry information for:

A

1) take over host cell machinery, 2) make new capsomere proteins, 3) enzymes needed for viral replication

46
Q

4 qualities of viral genomes

A

1) DNA or RNA, 2) Single or double stranded, 3) single or segmented sections, 4) circular or linear

47
Q

DNA viruses usually have single or double stranded DNA?

48
Q

RNA viruses usually have single or double stranded RNA?

49
Q

Who establishes rules for viral classification?

A

International Committee on taxonomy of viruses (ICTV)

50
Q

What properties group viruses?

A

1) Type of nucleic acid present (DNA or RNA), 2) Capsid symmetry (helical, icosahedral, or complex), 3) presence or absence of envelope, 4) Genome architecture (ssDNA, ssRNA, etc.)

51
Q

Is viral classification part of the binomial nomenclature system?

A

No- only order, family, genus, species levels included

52
Q

Viruses are often referred to by their…

A

Common name

53
Q

How is viral replication done typically?

A

Hijack host cell machinery- enzymes, proteins, energy from the host is used to make new virions

54
Q

How do bacteriophages replicate?

A

Lytic pathway or lysogenic pathway

55
Q

Lytic Pathway

A

Results in active virion production, kills the host

56
Q

Lysogenic pathway

A

viral DNA hides in the host, doesn’t kill the host, until it enters the lytic pathway

57
Q

Bacteriophage Lytic Replication Cycle

A

Active viral replication, kills host bacterial cell

58
Q

5 stages of bacteriophage lytic replication cycle

A

1) Attachment (adsorption): Phage binds to bacterial cell
2) Penetration (entry): Phage injects genetic material into the cell
3) Replication (synthesis): Phage commandeers host cell factors to transcribe and translate viral genes
4) Assembly (maturation): Genome packed into capsid and phage structures assembled
5) Release: Bacterial cell lyses and new phages are released

59
Q

Lysogenic Replication cycle

A

Not all bacteriophages can go into lysogen. Lysogenic replication by temperate phages. Prophages are able to confer new pathogenic properties to bacterial cells (i.e. phage conversion)

60
Q

Steps of lysogenic replication

A

1) Attachment
2) Penetration
3) Phage genome is incorporated into the host cell genome, forming a prophage
4) As the cell divides, it copies the prophage
5) Host cell is stressed, the prophage may excise itself from the host genome
6) Phage enters the lytic replication pathway

61
Q

True/ False: prophages are able to confer new pathogenic properties to bacterial cells

A

True, this is called phage conversion. For example, can provide new pathogenicity factors to a bacterium (toxins). Corynebacterium diphtheria and clostridium botulinum are examples.

62
Q

6 Steps of Animal virus replication pathway:

A

1) Attachment: interaction between spikes/ capsomere and host membrane proteins
2) Penetration: by fusion or endocytosis
3) Uncoating: removal of capsid coat
4) Replication: Genome is replicated and viral proteins are made
5) Assembly: new viral particles are made
6) release by budding or lysis

63
Q

Host Range

A

a collection of species that a virus can infect. Some can infect more than one, while others infect only one species

64
Q

Examples of a virus that only infects one species

65
Q

What does host range depend on?

A

The ability of a virus to attach to host cell

66
Q

Tropism

A

Range of tissues and cell types a virus can infection one host

67
Q

Acute infections

A

Viruses infect a host cell and new visions are made

68
Q

Persistent infections

A

Viruses that replicate without being cleared by the immune system. Can be chronic or latent

69
Q

Chronic

A

low level of virus produced throughout (HIV), constant production

70
Q

Latent

A

Periods of activity and inactivity (Herpes)

71
Q

Oncogenic Viruses

A

Cause cancer by stimulating uncontrolled host cell division/ decreasing host cell responsiveness to death signals

72
Q

What percent of cancer is caused by oncoviruses?

73
Q

Examples of oncoviruses?

A

Human papilloma viruses (HPVs), Human t-lymphotropic viruses (HTLV)

74
Q

Why would we want to cultivate viruses?

A

To develop vaccines and drugs to combat these viruses, researchers must grow them in a laboratory setting

75
Q

What is required to grow viruses in the lab?

A

A specific host cell: bacterial lawns for bacteriophages, animal cell culture for animal viruses, bird embryos (live animals sometimes needed)

Rachel Microbiology (2 decks)

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