Microbiology > Viruses > Flashcards

Viruses Flashcards

(90 cards)

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1
Q

What are the four types of acellular agents?

A

Viruses, Viroids, Satellites, Prions

Each type has distinct structural and functional characteristics.

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2
Q

What is a major cause of disease in all organisms?

A

Viruses

Viruses also serve as a new source of therapy and are important in evolution.

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3
Q

What is a virion?

A

Complete virus particle consisting of nucleic acid enclosed in a protein coat

A virion may have additional layers and cannot reproduce independently.

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4
Q

What types of cells can virions infect?

A

Bacterial, archaeal, and eukaryotic cells

Eukaryotic cells include plants, animals, protists, and fungi.

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5
Q

How are viruses classified?

A

Based on genome structure, life cycle, morphology, genetic relatedness

This classification helps in understanding the diversity of viruses.

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6
Q

What is the size range of virions?

A

~10–400 nm in diameter

Most viruses must be viewed with an electron microscope due to their small size.

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7
Q

What does a nucleocapsid consist of?

A

Nucleic acid and a protein coat (capsid)

Some viruses consist only of a nucleocapsid, while others have additional components.

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8
Q

What is the function of a viral capsid?

A

Protects viral genetic material and aids in transfer between host cells

Capsids are composed of protein subunits called protomers.

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9
Q

What are the shapes of capsids?

A

Helical, icosahedral, complex

Capsids can be shaped like hollow tubes with protein walls.

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10
Q

What is a viral envelope?

A

An outer, flexible, membranous layer

Animal virus envelopes usually arise from the host cell plasma or nuclear membrane.

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11
Q

True or False: Viruses can reproduce independently of living cells.

A

False

Viruses cannot carry out cell division and must infect host cells to replicate.

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12
Q

Fill in the blank: Capsids are made of protein subunits called _______.

A

protomers

Protomers self-assemble to form the capsid.

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13
Q

Who first proposed the term “virus” and what does it mean?

A

Martinus Beijerinck; it means “poison.

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14
Q

What are bacteriophages?

A

Viruses that infect bacterial cells

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15
Q

All virions contain a __________ made of nucleic acid and a protein coat.

A

nucleocapsid

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16
Q

True or False: All viruses contain an envelope

A

False; only some viruses are enveloped; others are nonenveloped/naked

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17
Q

Define a virion

A

A complete virus particle consisting of nucleic acid (DNA or RNA) enclosed in a protein coat

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18
Q

True or False: A virion is capable of extracellular existence

A

True

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19
Q

What makes prions different from viruses?

A

Prions only contain protein, and no nucleic acid

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20
Q

What is the main function of the viral capsid?

A

To protect viral genetic information

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21
Q

The protein coat of a virus is called a ________

A

capsid

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22
Q

What distinguishes enveloped viruses from nonenveloped viruses?

A

Enveloped viruses have a lipid membrane surrounding the capsid; nonenveloped do not.

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23
Q

What are viral spikes?

A

Glycoprotein projections on the viral envelope used for attachment and entry into host cells.

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24
Q

True or False: Viral genomes can only be DNA

A

False

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25
Name the four possible formats of viral genomes
Double stranded Single stranded Linear Circular
26
Capsids can have three types of symmetry: helical, __________, or complex.
icosahedral
27
Who proposed the Baltimore classification system?
David Baltimore
28
True or False: All Baltimore classes are distinguished by the presence or absence of an envelope.
False – classification is based on nucleic acid type and replication strategy, not envelope.
29
Fill in the blank: Baltimore Class I viruses have __________-stranded __________ genomes.
Double stranded DNA
30
Q: Q: Give an example of a Class I (dsDNA) virus family.
Adenoviridae
31
What type of genome do Class II Baltimore viruses have?
Single stranded DNA genome
32
Q: True or False: Class III viruses contain single-stranded RNA genomes.
A: False – Class III viruses have double-stranded RNA (dsRNA).
33
What makes Class VI (Retroviruses) unique?
They use reverse transcriptase to convert RNA into DNA during replication.
34
What enzyme is essential for Class VI retrovirus replication?
Reverse transcriptase
35
Why can virions exist extracellularly even though viruses aren’t alive?
Because virions are inert, fully assembled particles with protective capsids (and envelopes) that allow them to survive outside cells, even though they cannot reproduce without a host.
36
Name two structures of viruses that a part of the central core of a virus particle:
Matrix proteins and nucleic acid molecules
37
Genomes can be _______ or _________.
segmented; circular
38
BC V genomes have ______________RNA genomes
negative sense
39
What is the main purpose of viral multiplication?T
To make new viral particles that go on to invade host cells
40
Which step of viral multiplication involves the hijacking of the host cell by the virus?
Sythesis
41
Which structure of the virus is important in gaining entry into the host cell?
Glycoprotein spikes
42
True or false: How a virus attatches to a host cell depends on whether the virus is enveloped or naked
True
43
Which stage of viral multiplication involves the cell membrane folding inward to engulf the viral cell?
Penetration
44
What structure does the host cell membrane form when it engulfs a virus during endocytosis?
Vesicle
45
Some viruses can integrate their genome into the host’s DNA. Which cycle does this occur in?
Lysogenic cycle
46
Whats the difference between lytic and lysogenic cycle?
In the lytic cycle, the host cell is destroyed and new viral cells are made quickly In the lysogenic cycle, the host cell replicates along with viral DNA and the virus hides within the host cells
47
Give an example of a type of virus that has a lysogenic cycle
Retroviruses
48
During which stage of viral multiplication does a virus integrate its genome into the host DNA (lysogenic cycle)?
After penetration and uncoating
49
In an animal cell, a virus that conducts the lysogenic cycle is called a _________.
Provirus
50
True or False: Viruses that only undergo the lytic cycle do not integrate into host DNA.
True
51
True or False: Maturation is the final step where the virus becomes fully infectious.
True
52
During assembly, viral ________ and ________ come together to form new virions.
Proteins; genome
53
Name some viral proteins:
Capsid proteins, glycoproteins, and enzymes
54
Where in the host cell does synthesis occur for DNA viruses?
The host cell's nucleus
55
What are the two different methods of viral release?
Lysis and budding
56
What are the two methods of viral penetration?
endocytosis and membrane fusion
57
True or False: All viruses can undergo lysogenic cycles.
False; only retroviruses can under lysogenic cycles
58
What does the host cell provide during synthesis?
Ribosomes, enzymes, nucleotides, energy (ATP)
59
Why is uncoating essential before synthesis?
Genome must be exposed to be replicated
60
Budding is used by non-enveloped viruses.
False
61
Explain budding
Virion propels out of a host cell with a piece of the host cell membrane and it becomes part of it's envelope
62
Non enveloped viruses _____ the host cell when they exit
lyse
63
True or False: An enveloped virus must take a part of the host cell membrane - no other part
False
64
Bacteriophages only infect bacteria
False - they can also infect archae
65
You can grow bacteriophages in ______ and _______ cultures
broth and agar
66
Animal viruses grow in _________ culture
tissue cell
67
Name two visible effects or damages that viruses can cause to host cells.
Cells can shrink or fuse together
68
Viruses that cause cancer are called ________viruses
oncogenic
69
What is neoplasia?
Uncontrolled cell growth
70
How can a virus cause cancer?
Viruses insert their DNA into host cells, disrupt the normal processes of the host cell, and hijack cell signals that control growth, making them divide uncontrollably.
71
Name an example of a cancer causing virus
Human Papillomavirus (HPV), leading to throat cancer
72
What are oncogenes?
Cancer causing genes
73
True or False: antibiotics for bacteria can also work on viruses
False
74
What are virions?
Tiny, infectious, naked circles of single-stranded RNA
75
Which of the following do viriods have? -Capsid -Protein synthesis abilities - Genes
NONE!
76
What part of the host cell do virions depend on for replication
host cell RNA polymerase
77
What is the main characteristics of satelites?
They depend on other viruses to replicate and cannot replicate alone
78
True or False: Satellites can have DNA or RNA
True
79
Prions, also known as:
Proteinaceous Infectious particles
80
What type of proteins do prions attack and corrupt?
PrPC
81
Where is PrPc found?
In the brain, brain tissue
82
True or False: There is a cure for prion related diseases and most are survivable
False: No cure, death is imminent
83
_________ is the defective form of PrPC
PrPSc
84
Name two prion related human diseases
Kuru and and CJD
85
Capsids surround the __________.
Nucleic acids
86
Viral envelopes surround the ______ capsid.
87
True or False: Bacteria are much smaller than viruses
False
88
Virion release occurs via:
Budding and Lysis
89
How do you cultivate plant viruses?
(plant)tissue and protoplast
90
Microbiology
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