Ch. 6: Viruses

Question 1

the function of viral spikes

Answer 1

responsible for attaching to a host cell

-determines the host range [which organisms can be affected]

-determines tropism [which cell types it can infect]

Question 2

where are viral spikes found?

Answer 2

in a naked virus: on the capsid

in an enveloped virus: on the outer envelope

Question 3

What are the 2 main virus structures?

Answer 3

helical & icosahedral

Question 4

Virus

Answer 4

infectious agent of small size and simple composition that can multiply only in living cells of animals, plants, or bacteria.

-obligate intracellular parasites of any cell type- bacteria, fungi, algae, protozoa, plants, animals

-not considered alive, not cellular in nature; all exactly the same, can be cultured in a lab

Instead of saying alive or dead, it is active or inactive..

Question 5

identify this

Answer 5

bacteriophage

Question 6

What are the 6 steps of animal cells multiplying?

Answer 6

1) Adsorption- using viral spikes, will attach to host cell; glycoprotein attachment

2) Penetration- being engulfed or [direct fusion only w/ enveloped viruses, envelope fuses with]

[2 and 3 can occur together with direct fusion]

3) Uncoating- dissolving of vesicle, envelope, and capsid

4) Synthesis- making all the parts of virus [capsomers, nucleic acid copying, spikes…]

5) Assembly- bringing all parts together, capsid forms from capsomers, nucleocapsid, spikes inserted in membrane or nucleocapsid

6) Release- virion buds off or [lysis only with naked viruses]

A[PU]SAR

Question 7

What are some consequences of viral infections in humans?

Answer 7

cytopathic effects- CPE

-can be seen in a cell in a light microscope; unique to virus

-Inclusion bodies can appear in cytoplasm; multinucleate cell [unusual], cell enlargement

Question 8

why are CPE’s important? [cytopathic effects]

Answer 8

Diagnostic medicine

in the past, it was important for viral infection diagnosis by looking at cells under microscope; they are unique to virus and visible under microscope

Question 9

Helical and icosahedral are terms used to describe the shapes of a virus’s __________

Answer 9

capsid

Question 10

Host range is limited by the _________________

Answer 10

viral spikes

Question 11

Viruses that consist of only a nucleocapsid are considered:

Answer 11

naked viruses

Question 12

Viral capsids are made from subunits called:

Answer 12

capsomers

Question 13

Can viruses be seen with a light microscope?

Answer 13

most can NOT be seen

Question 14

The core of every virus particle always contains:

Answer 14

Either RNA or DNA [not both]

Four choices: ssDNA, dsDNA, ssRNA, dsRNA

Question 15

Which structures are used by bacteriophages to attach to host cell receptors?

Answer 15

tail fibers

Question 16

___________ can be activated into viral replication and enter the lytic cycle.

Answer 16

Prophages

Question 17

How do enveloped animal viruses exit their host?

Answer 17

budding or exocytosis

Question 18

The virus-induced, specific damage to the host cell that can be seen in a light microscope is called

Answer 18

cytopathic effect.

Question 19

Epstein-Barr virus, HPV, Hepatitis B virus are all :

Answer 19

Oncogenic viruses

Question 20

Infectious prions differ from non-infectious prions in their:

Answer 20

secondary and tertiary structures

Question 21

virion

Answer 21

an elementary virus particle in its complete morphological & therefore infectious form

-it consists of a nucleic acid core surrounded by capsid, which may be enclosed in an envelope

Question 22

adsorption

Answer 22

process of adhering one molecule onto surface of another molecule

[Animals with the spikes and bacteriophages with tail fibers]

Question 23

cytopathic effect

Answer 23

degenerative changes in cells associated with virus infection

Ex) formation of multinucleate giant cells (negri bodies) , prominent cytoplasmic inclusions of nerve cells infected by rabies virus

Question 24

latency

Answer 24

state of being inactive and not multiplying

ex) latent virus

Question 25

bacteriophage

Answer 25

a virus that specifically infects bacteria

phage means = to eat

naked- no membrane

Question 26

in vitro

Answer 26

literally means “ in glass “ signifying a process or reaction occurring in an artificial environment, as in a test tube or culture medium

Question 27

in vivo

Answer 27

literally means “ in a living being “ signifying a process or reaction occurring in a living thing

Question 28

viroid

Answer 28

an infectious agent that (unlike a virion) lacks a capsid and consists of a closed circular RNA molecule

[mostly plant pathogens, but animal versions may exist]

Question 29

prion

Answer 29

infectious protein that can replicate; associated with the slow virus spongiform encephalopathies of humans and animals

[a misfolded protein that can transmit its misfolded shape onto normal variants of the same protein. Prions are the causative agent of several transmissible and fatal neurodegenerative diseases in humans and other animals]

-lacking nucleic acids

BSE mad cow disease
-scrapie -CJD -vCJD -Kuru -fatal familial insomnia–

Question 30

obligate intracellular parasite

Answer 30

A parasite such as a virus or rickettsia that can reproduce only when within a living cell, although it may survive outside cells

Question 31

capsid

& what is it made of?

Answer 31

protein shell that encloses the nucleic acid; with its enclosed nucleic acid, it is called the nucleocapsid.

-This shell is composed of protein organized in subunits known as capsomers

Question 32

naked virus

Answer 32

lacks a virus envelope

Question 33

viral envelope

Answer 33

the outermost layer of many types of viruses.

-protects the genetic material in their life cycle when traveling between host cells.

Question 34

oncoviruses

Answer 34

virus that can cause cancer.

=Epstein-Barr virus (EBV), human T-lymphotropic virus 1, hepatitis B virus, hepatitis C virus, HIV, human papilloma virus (HPV), and human herpesvirus 8 (HHV-8).

Question 35

viral plaque

Answer 35

a visible structure formed after introducing a viral sample to a cell culture grown on some nutrient medium.

-The virus will replicate and spread, generating regions of cell destruction known as plaques.

Question 36

T4 bacteriophage only infects:

Answer 36

E. Coli