microbio chapter 6 part 2

Term
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General Morphological Symmetry of Capsids
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Terms in this set (23)
General Morphological Symmetry of Capsids
Icosahedral capsid
Helical capsid
Complex Viruses
Icosahedral capsid
6
-a "3D" look
-looks spherical when viewed (nature's favorites)
-These capsids form an icosahedron
-a three-dimensional, 20-sided figure with 12 evenly spaced corners.
-The arrangements of the capsomeres vary from one virus to another.
-for example, a poliovirus has 32, and an adenovirus has 252 capsomeres.
Helical
4
-look like a hollow cylinder
-they infect tobacco plants (tobacco mosaic virus)
-have rod-shaped capsomeres that bond together to form a series of hollow discs resembling a bracelet.
-During the formation of the nucleocapsid, these discs link with other discs to form a continuous helix into which the nucleic acid strand is coiled.
Complex viruses
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-have tails or multilayered walls surrounding the nucleic acid
-found in bacteriophage
-bacteriophage: the viruses that infect bacteria
-Have multiple types of proteins
-Take shapes that are not symmetrical
Host Range
A virus can invade its host cell only through making an exact fit with a specific host molecule
Restricted host range example
hepatitis B only infects liver cells of humans
Moderately restrictive host range example
poliovirus infects intestinal and nerve cells of primates
Broad host range example
rabies virus infects various cells of all mammals
General phases in the life cycle of animal viruses in order:
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1. Adsorption
2.Penetration
3. Uncoating
4. Synthesis
5. Assembly
6. Release
Adsorption
2
-attachment of viruses to host cells
-invasion begins when the virus encounters a susceptible host and adsorbs specifically to receptor sites on the host cell membrane
Penetrationenters a host cellUncoating 2-come out of coat so it can synthesize -enzymes in the vacuole dissolve the envelope and capsid, releasing the virus into the cytoplasmSynthesismake more virus particlesAssemblyviral DNA is put into protein coatRelease 3-leave the host cell by exocytosis -envelopes are formed ( remember that sometimes it can take with it part of the host cells cell membrane so it has an envelope around it)Prions 2-infectious protein particles -smaller than virusesViroidsNaked RNA (affects plants)Virulent phageKills the hostTemperate phageviruses that infect a bacteria and form a lysogenic or lytic relationshipLysogenicdoes not kill the host cell right awayLyticthe virus causes the cell'sInductionthe move to lytic from lysogenicTransductionincludes DNA from previous host.