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51 Cards in this Set
- Front
- Back
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Name the components of a virus
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Nucleic acid
protein coat sometimes an envelope (lipid membrane) |
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What is a virion?
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Infectious virus particle
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What is the size of a virus?
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20 - 500 nanometers
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What machinery does a virus need?
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Enzymes to synthsize amino acids
Enzymes that generate ATP Ribosomes, tRNAs and enzymes for protein synthesis Membranes to concentrate macromolecules, small molecules and ions |
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Why study viruses?
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impt disease causing agents
all life forms can be infected can be engineered to prevent/cure disease reveal gene expression, cell physiology, intracellular signaling pathway |
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What is an obligatory intracellular parasite?
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an organism that can only replicate within living cells
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Virus replication is different from other obligatory intracellular parasites because?
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the viral particle breaks down and releases it genome. Other organisms remain intact, retain their genome, replicate w/i own membrane
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The smallest viruses have a diameter of ______ , genome of ________nucleotides, and code for ______ proteins
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20 nm
2000 nucleotides 2 proteins |
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The largest viruses have a diameter of ________, genome of __________nucleotides, and code for ________proteins.
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500 nm
1.2 million nucleotides 1200 proteins |
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Viruses are the only life form that have ______ genomes
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RNA
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Retrovirus family
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HIV-1,
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Papillomavirus family
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HPV 16, 18, 31
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Herpesvirus
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Varicella virus, HSV-1, HSV-2, EBV, CMV
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Adenovirus
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adenoviruses
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Coronavirus
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coronaviruses, SARS,
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Picornavirus
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Rhinoviruses, Hep A, Polio virus type 1,2,and 3
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Calcivirus
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Norwalk virus,
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Reovirus
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Rotaviruses
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Flavivirus
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Dengue Virus, Yellow fever
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Othomyxovirus
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Influenza A and B
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Paramyxovirus
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Measles, mumps
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Rhabdovirus
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Rabies virus
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Poxvirus
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variola
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MOI
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multiplicity of infection - the number of incetious virus particles added per susceptible cell (usually 10 - 100 pfu per cell)
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tropism
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the ability of a virus to infect and replicate in a particular tissue organ or species. Often depends on interaction of the virion with the receptors
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Baltimore classifications
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+ssRNA, -ssRNA, dsDNA, ss/dsDNA, ssDNA, dsRNA
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+strand RNA genomes
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mRNA's directly enter cell
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-strand RNA genomes
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must synthesize + strand RNA's(mRNA). Virus must supply RNA dependent RNA polymerase
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dsRNA genomes
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Virus must bring RNA dependent RNA polymerase (RDRP) along with it to synthesize mRNA's
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dsDNA genomes
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cellular RNA pol recognizes viral DNA and synthesizes viral mRNA
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ssDNA genome
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Cellular DNA pol sythesizes ss into ds and then it is transcribed by cellular RNA pol to mRNAs (some virions bring own RNA pol)
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+ss RNA genome (retrovirus)
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+strand used to make ds genome using reverse transcriptase, and then on to mRNA.
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Early proteins of many DNA viruses _______
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interact with cell signalling pathway to direct the cell to start DNA synthesis(S) phase.
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Late mRNA's are made from
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newly replicated genomes
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Late viral proteins are involved in
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capsid assembly and viral genome packaging
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scaffolding proteins
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involved in virion assembly but then discarded and are not part of the new virion
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Budding
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formation of envelope, from cell membrane, around viral particle.
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virus particle
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molecular structures that package virus genomes in infected cells and transmit them to new host cells.
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Virion
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complete infectious virus particle
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Name 5 essential functions to virion transmission
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1)be correctly assembled
2)escape the cell in which they are made 3)withstand the extracellular environment 4)attach to and enter another cell 5)release the viral genome |
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capsid
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rigid symmetrical containers
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nucleocapsid
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nucleic acid packaged within the capsid
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uranyl acetate
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used for negative staining by EM
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Icosahedral symmetry accommodates ______ sturctural subunits
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60
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An icosahedron has ______ five fold rotation axes
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12
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An icosahedron has _______ 3 fold rotation axis
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20
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An icosahedron has ______ 2 fold rotation axis
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30
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T =
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h2 + hk +k2
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Type I integral proteins
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N-terminus facing outward and the transmembrane anchor nearest the C terminus
signal sequence is cleaved |
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Type II integral proteins
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C-terminus facing outward and the anchor near the inward-facing N terminus
transmembrane anchor serves as signal for membrane insertions |
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HIV-1 budding is assembled from
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Gag precursor cleavage at the membrane during budding
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