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37 Cards in this Set
- Front
- Back
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T or F
Viruses can have both DNA and RNA |
False. They can have either or. Never both.
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T or F
All viruses evolved from a single progenitor. |
False.
They arose independently then continued to diversify. |
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How are viruses seen?
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electron microscopy with negative staining
X-ray crystallography |
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What is a virion?
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The complete virus particle
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What are loops?
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chains of amino acids that project from the virus. Some can interlock for stabilization, or are involved with attachment to host cell and are antigenic
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Capsid
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morphologically defined protein coat
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Nucleocapsid
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capsid + enclosed nucleic acid
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envelope
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liproprotein covering
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capsomers
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descernible features seen on the surface of virions by EM
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Hierarchy of capsid assembly
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protein subunits form structural units
structural units form assembly units assembly units form capsids |
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What is "self assembly"?
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Process where structural units are brought into position by random thermal movement and are put into place by weak chemical bonds.
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What are the two kinds of virion symmetry?
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Icosahedral
Helical |
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Icosahedral symmetry
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12 corners (vertices)
30 edges 20 faces - EQUILATERAL TRIANGLES |
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Why icosahedral symmetry?
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optimum solution for assembling repeating subunits into a strong enclosure enclosing a maximal volume.
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hexons
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6 neighboring capsomers
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pentons
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5 neighboring capsomers at the vertices
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Helical Symmetry
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arranged as a helix, identical protein-protein interfaces on the structural units. Forms a spiral.
Animal viruses are wound into secondary coil and have an envelope |
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lipoprotein envelope
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needed for infectivity
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budding
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outer layer formed when nucleocapsid is extruded
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Where do the lipoproteins for the envelope come from?
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Lipid - from the cellular membrane of the host cell
Protein - virus coded |
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What to envelope associated proteins do?
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receptor binding
membrane fusion uncoating reception destruction |
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peplomers or spikes
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glycoproteins that form the envelope
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Fusion proteins
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glycosylated
viral entry and release |
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Matrix proteins
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add rigidity to virion
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What is viral uncoating?
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an intracellular step during which viral nucleic acid and capsid are separated
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How many proteins can a virus encode?
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1 - smallest virus
5-10 many important viruses <200 poxviruses and herpes |
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What is viral uncoating?
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an intracellular step during which viral nucleic acid and capsid are separated
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Monopartite
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all viral genes contained in a single molecule of nucleic acid
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multipartite
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segmented
genes distributed in multiple molecules of nucleic acid |
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What is the range of viral genome sizes?
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1.7kb to +200kb
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What is positive sense RNA?
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RNA that can direct the synthesis of a protein
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What is negative sense RNA?
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a nucleotide sequence that is complementary to that of mRNA. must posses an RNA polymerase which will transcribe the +sense RNA in the host cell
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What is ambisense RNA?
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One part of the RNA segment is positive sense, the other negative sense
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T or F
All viral envelopes are the same. |
False.
Different virions take their lipid from different parts of the cell. Some use the plasma membrane, others use intracytoplasmic organelles. |
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T or F
Freezing kills viruses. |
False
Viruses are stored at low temperatures to preserve them. |
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T or F
Boiling kills prions. |
False. Prions survive boiling, freezing, and large doses of gamma irradiation.
SCARY |
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T or F
Enveloped viruses are more heat labile than nonenveloped viruses. |
True. Good to know...
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