Ch. 6: Viruses Flashcards
the function of viral spikes
responsible for attaching to a host cell
-determines the host range [which organisms can be affected]
-determines tropism [which cell types it can infect]
where are viral spikes found?
in a naked virus: on the capsid
in an enveloped virus: on the outer envelope
What are the 2 main virus structures?
helical & icosahedral
Virus
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..
identify this
bacteriophage
What are the 6 steps of animal cells multiplying?
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
What are some consequences of viral infections in humans?
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
why are CPE’s important? [cytopathic effects]
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
Helical and icosahedral are terms used to describe the shapes of a virus’s __________
capsid
Host range is limited by the _________________
viral spikes
Viruses that consist of only a nucleocapsid are considered:
naked viruses
Viral capsids are made from subunits called:
capsomers
Can viruses be seen with a light microscope?
most can NOT be seen
The core of every virus particle always contains:
Either RNA or DNA [not both]
Four choices: ssDNA, dsDNA, ssRNA, dsRNA
Which structures are used by bacteriophages to attach to host cell receptors?
tail fibers
___________ can be activated into viral replication and enter the lytic cycle.
Prophages
How do enveloped animal viruses exit their host?
budding or exocytosis
The virus-induced, specific damage to the host cell that can be seen in a light microscope is called
cytopathic effect.
Epstein-Barr virus, HPV, Hepatitis B virus are all :
Oncogenic viruses
Infectious prions differ from non-infectious prions in their:
secondary and tertiary structures
virion
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
adsorption
process of adhering one molecule onto surface of another molecule
[Animals with the spikes and bacteriophages with tail fibers]
cytopathic effect
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
latency
state of being inactive and not multiplying
ex) latent virus
bacteriophage
a virus that specifically infects bacteria
phage means = to eat
naked- no membrane
in vitro
literally means “ in glass “ signifying a process or reaction occurring in an artificial environment, as in a test tube or culture medium
in vivo
literally means “ in a living being “ signifying a process or reaction occurring in a living thing
viroid
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]
prion
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–
obligate intracellular parasite
A parasite such as a virus or rickettsia that can reproduce only when within a living cell, although it may survive outside cells
capsid
& what is it made of?
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
naked virus
lacks a virus envelope
viral envelope
the outermost layer of many types of viruses.
-protects the genetic material in their life cycle when traveling between host cells.
oncoviruses
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).
viral plaque
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.
T4 bacteriophage only infects:
E. Coli
