Talaro Ch. 6 Microbiology

Front 1

T or F
Viruses only infect human and mammalian cells

Back 1

False. Viruses infect every kind of cell, including plants, bacteria, Protozoa, fungi, and animals.

Front 2

How do viruses survive outside a host cell?

Back 2

Viruses cannot survive outside a host cell. They are obligate intracellular parasites.

Front 3

Describe a helical capsid

Back 3

Have rod-shaped capsomers that form a series of hollow discs that look like a bracelet

Front 4

Describe an icosohedron

Back 4

3D, 20 sides with 12 evenly spaced corners

Front 5

The capsid of any virus is constructed from a number of identical protein subunits called ___________.

Back 5

Capsomers

Front 6

What component is essential for attachment to host cells in regard to their viral envelopes?

Back 6

Spikes or peplomers

Front 7

T or F
All viruses are pleomorphic

Back 7

False. Enveloped viruses arecmore flexible, while naked viruses are rigid due to their capsid.

Front 8

Name the very large DNA viruses that LACK typical capsids and are covered by a dense layer of lipoproteins and course fibrils.

Back 8

Poxvirus

Front 9

Describe the structure and function of bacteriophages

Back 9

Structurally, they contain a polyhedral capsid head as well as helical tail and fibers for attachment to the host cell. They parasitize bacteria and make them "meaner"

Front 10

Are viruses known to contain DNA or RNA typically?

Back 10

They can contain either but not both.

Front 11

Why is AIDS (retrovirus) different than other viruses?

Back 11

It uses reverse transcriptase to change RNA to DNA

Front 12

What is the function of a polymerase?

Back 12

Synthesis of DNA and RNA and replication of RNA

Front 13

Name, in order, the stages of viral multiplication

Back 13

Adsorption (attachment)
Penetration
Synthesis
Assembly
Release

Front 14

During adsorption, the membrane receptors attach to ___________.

Back 14

Glycoproteins

Front 15

The rabies virus attaches to receptors found on what type of cell?

Back 15

Mammalian nerve cells

Front 16

The human immunodeficiency virus attaches to what?

Back 16

CD4 protein on certain white blood cells

Front 17

Viruses target different cells. What cells do the hepatitis B virus target? What about mumps?

Back 17

Hep B....liver cells
Mumps....salivary glands

Front 18

How long have oceanic viruses been researched?

Back 18

A decade

Front 19

Based on research, how many distinct virus types have most likely not yet been described?

Back 19

Hundreds of Thousands

Front 20

Describe two viewpoints taken with viruses.

Back 20

1. Viruses are unable to exist independently from a host cell, so are not considered living things.

2. Viruses are more than inert, lifeless molecules because they are seen to have the ability to direct the few life processes they do posess.

Front 21

How are viruses described, given their unique position in the biological spectrum?

Back 21

Viruses are infections particles (not organisims), and described as either active or inactive (instead of dead or alive).

Front 22

Name the two types of arrangements for viral capsids.

Back 22

Helical and Icosahedral

Front 23

How does a viral envelope form?

Back 23

When enveloped viruses are released from the host cell they take on some of its membrane in the form of an envelope.

Front 24

What is a genome?

Back 24

A genome is the sum total of the genetic information carried by any organism. It is carried and expressed via nucleic acids.

Front 25

T or F
A virus contains many more genes than a cell.

Back 25

False. A virus carries many less genes than a cell does. For example, HIV carries 9 genes, a human cell carries 25,000.

Front 26

How is double stranded DNA arranged?

Back 26

dsDNA can be arranged linearly or in circles.

Front 27

How many genes does the bacterial cell E. coli carry?

Back 27

approximately 4,000

Front 28

Why are viruses said to be "efficient"?

Back 28

Viruses contain only the genes necessary for invading host cells and to redirect activity to make new viruses. They do not possess the genes necessary for protein synthesis or metabolism (no waste).

Front 29

Give examples of 2 complex viruses.

Back 29

1. Poxvirus
2. flexible-tailed bacteriophages

Front 30

Give 2 examples of enveloped viruses with helical nucleocapsids

Back 30

1. mumps virus
2. rhabdovirus

Front 31

Give 2 examples of enveloped viruses with icosahedral nucleocapsids.

Back 31

1. herpes virus
2. HIV (AIDS)

Front 32

Give an example of a naked viruses with a helical capsid.

Back 32

plum poxvirus

Front 33

Give 2 example of naked viruses with icosahedral capsids.

Back 33

1. poliovirus
2. papillomavirus

Front 34

What is the term used to describe single-stranded RNA that is ready for immediate translation into proteins.

Back 34

Positive-strand RNA

Front 35

What is negative-strand RNA?

Back 35

RNA genomes that still need to be converted to a proper form for translation.

Front 36

Why are viruses considered to be genetic parasites?

Back 36

Viruses cannot multiply until their nucleic acid has reached the internal habitat of a host cell.

Front 37

What genes are mandatory for viral existence?

Back 37

1. genes for synthesizing the viral capsid and genetic material
2. genes for regulating the actions of the host
3. genes for packaging the mature virus

Front 38

What genes do viruses LACK?

Back 38

Genes for synthesis of metabolic enzymes (no metabolism=no waste=very efficient)

Front 39

How does adsorption occur?

Back 39

Adsorption occurs when a virus attaches to a host cell by specific binding of its spikes (peplomers) to cell receptors.

Front 40

Explain penetration and uncoating in regard to viruses.

Back 40

During penetration, the virus is taken into a vesicle and its envelope is uncoated to release the RNA via enzymes in the cytoplasm.

Front 41

What are two ways penetration occurs? Explain each.

Back 41

1. Fusion--viral envelop fuses to host cell membrane
2. Endocytosis--virus is engulfed into a vesical after initial attachment

Front 42

What is the distinguishing factor between fusion and endocytosis?

Back 42

Fusion can only occur with ENVELOPED viruses. Endocytosis can occur with either naked OR enveloped viruses.

Front 43

List the basic steps of viral synthesis.

Back 43

1.RNA of the virus becomes message for translation.
2. Negative-strand RNA must be converted to Positive-strand RNA message
3. Under viral control, the host synthesizes new components:
--RNA molecules
--capsomers
--spikes

Front 44

Immediately upon entry, what is the first thing a viral nucleic acid does?

Back 44

Alters the genetic expression of the host and controls it to synthesize the building blocks for new viruses.

Front 45

What occurs during assembly?

Back 45

Viral spike proteins are inserted into the cell membrane for the viral envelope.

Nucleocapsid is formed from RNA and capsomers.

Front 46

What are the two ways viruses leave their host cell upon release?

Back 46

Naked and complex viruses leave through cell lysis (rupturing)

Enveloped viruses are released via budding or exocytosis.

Front 47

What is a virion?

Back 47

A mature, extracellular virus particle that is virulent and able to cause infection in a host cell.

Front 48

Describe CPEs

Back 48

Cytopathic effects (CPEs) describe virus-induced damage to the cell that alters it's microscopic appearance.

Front 49

What are inclusion bodies?

Back 49

Compacted masses of viruses or damaged cell organelles.

Front 50

Explain the term syncytia.

Back 50

Syncytia is one common CPE that is the fusion of multiple host cells into a single large cell containing multiple nuclei.

Front 51

How do "persistent infections" act?

Back 51

Most viruses kill the host cell, but in this case the cells escape destruction by harboring the virus. These infections last from a few weeks to years.

Front 52

What is "latent state"? Give an example of a virus that goes into a latent state.

Back 52

If a virus is in a latent state, it is inactive over a long period of time. Examples include herpes zoster, and herpes simplex, both which go into latency in nerve cells.

Front 53

What is the term for a virus that permanently alters a host cell's genetic material? What does it cause?

Back 53

Oncogenic viruses; cancer.

Front 54

What is the term used to describe mammalian viruses capable of initiating tumors?

Back 54

Oncoviruses

Front 55

Give 2 specific examples of oncoviruses.

Back 55

1. Papillomavirus (associated with cervical cancer)
2. Epstien-Barr virus (causes Burkitt's lymphoma)
3. Hepatitis B virus (liver cancer)

Front 56

What is the significance of lysogeny?

Back 56

Lysogeny is less deadly to the cell than the full lytic cycle; it is thought to allow the virus to spread without killing the host.

Front 57

What was the first pathogen discovered in regard to lysogenic conversion? When was it discovered?

Back 57

Corynebacterium diphtheriae (causes diphtheria)--harmless without the phage; discvered in the 1950's

Front 58

What are "phages" responsible for?

Back 58

They make bacteria virulent by overtaking it and making it pathogenic when, normally, it may not have caused harm.

Front 59

What is the significance of prions?

Back 59

Prions belong to a group of their own. They are not viruses and are the only biologically active agent that lacks both DNA and RNA.

Front 60

What words are the term "prion" derived from? Why?

Back 60

"proteinaceous infectious" particle--its primary structure is a naked protein molecule.

Front 61

How long have we known about prions?

Back 61

30 years

Front 62

Diseases associated with prions are known as ___________ ____________ ___________. (Hint: TSEs)

Back 62

transmissable spongiform encephalopathies

Front 63

What is the mechanism of action of a prion?

Back 63

Upon contact with a normal protein, the prion can induce spontaneous abnormal folding in the normal protein which damages and kills the cell.

Front 64

How can prions be destroyed?

Back 64

They are extremely resistant to most forms of destruction (disinfectants, radiation, sterilization). Even extreme temperatures and concentrated chemicals are unreliable.

Front 65

Where are viroids found?

Back 65

In plants

Front 66

What is the structure of a viroid?

Back 66

Composed of naked strands of RNA, LACK a capsid or any other coating.

Front 67

What is the significance of viroids in the economy?

Back 67

Viroids are significant pathogen in economically important plants, such as tomatoes, potatoes, cucumbers, citrus, and chrysanthemums.

Front 68

What is the target of most prions. Name one example.

Back 68

Neural cells (brain); Creutzzfeldt-Jakob syndrome (CJS), in which the brain progressively deteriorates and motor coordination, sensory, and cognitive abilities are lost.

Front 69

What is the treatement for Creutzfeldt-Jakob syndrome?

Back 69

There is no treatment, most cases have been fatal.

Front 70

How is Creutzfeldt-Jakob syndrome contracted?

Back 70

It is thought that a variant of CJS appeared in Europe and is traced to eating meat from cows infected with the bovine form of encephalopathy.

Front 71

Do prions cause symptoms immediately? Explain.

Back 71

No. Diseases caused by prions have a long latent period (usually years) before symptoms of brain degeneration appear.

Front 72

How many capsomers do adenovirus have? Do all viruses with icosahedral capsids contain the same number? If not, explain.

Back 72

Adenovirus contains 242 capsomers. Not all viruses with icosahedral capsides contain the same number of capsomers (ie: poliovirus has 32), but they are all 3D, 20-sided and have 12 evenly spaced corners.

Front 73

Name 3 examples of human enveloped viruses

Back 73

influenza
measles
rabies

Front 74

Descibe the microscopic structure of HIV

Back 74

HIV is an enveloped virus with an icosahedral nucleocapsid.

Front 75

Describe the microscopic structure of Mumps virus

Back 75

Mumps virus is an eveloped virus with a helical nucleocapsid.

Front 76

Describe the structure of a plum poxvirus

Back 76

Plum poxvirus is a naked virus with a helical capsid.

Front 77

What is the structure of Poliovirus?

Back 77

Poliovirus is a naked virus with an icosohedral capsid.

Front 78

Describe the structure of a complex virus.

Back 78

Structures of complex viruses vary, however the consistent factor is that they are more intricate than a enveloped or naked viruses. For example, poxvirus is a large DNA virus that lacks a typical capsid, instead it is covered by a dense layer of liporoteins and course fibrils.

Front 79

What is the structure and type of the nucleic acid contained in parvovirus? Reovirus?

Back 79

Parvovirus contains single stranded DNA; Reovirus contains double-stranded RNA.

Front 80

Explain how viruses have adapted to assume total control over a cell's metabolic resources.

Back 80

Some can carry away substances from a host cell (ie: retrovirus borrows host's tRNA)

Front 81

What is the family name for influenza?

Back 81

Orthomyxoviridae

Front 82

Name the sickness caused by Varicellovirus

Back 82

Chicken pox

Front 83

What is the genus of the virus that causes a common cold?

Back 83

Rhinovirus

Front 84

What does Orthomyxoviridae cause? Paramyxoviridae?

Back 84

Influenza; parainfluenza

Front 85

What is the causative agent of HIV?

Back 85

Lentivirus

Front 86

What is Retroviridae?

Back 86

Family name of the causative agent "Oncornavirus" (genus) that causes T-cell leukemia

Front 87

Name the virus that causes Ebola fever

Back 87

Filovirus