Chapter+6 - Chapter 6 Virus Structure and Function General...

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Chapter 6- Virus Structure and Function General Properties of Viruses (virions) Obligate intracellular parasite made of nucleic acid surrounded by a protein coat. Only replicate inside host No nucleus, organelles, cytoplasm Viral genomes contain information for taking over host cell information for making viral proteins Capsid, genome replication proteins Virus Structure—Capsids Capsid- protein coat surrounding nucleic acid Capsid proteins are arranged to give virion symmetry Icosahedrol capsids Roughly spherical 20 equilateral triangles or faces Many animal viruses Filamentous capsids Long tube of protein, with genome inside Tube made up of hundreds of identical protein subunits Tube length reflects size of viral genome Complex capsids Many bacteriophage (viruses that infect bacteria) Asymmetrical (irregular) shapes Tend to be larger viruses Poxviruses Virus Structure—Envelopes Envelope- lipid bi-layer around capsid of some viruses Allows fusion to host cell or organelle membrane Only occurs if host cell not covered by cell wall Bacteriophages are NON-enveloped Envelope lipids come from host Not encoded by viral genome Proteins embedded in envelope may be encoded by virus Coats viral capsid as virus leaves cell or organelle Virus Structure—Genome DNA or RNA Single-stranded (ss) or double-stranded (ds) Linear or circular Includes genes encoding viral proteins Capsid Envelope proteins if virus is enveloped Any polymerase not found in host cell Bacteriophage Life Cycles 1. Attachment to host cell receptor proteins
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Bacterial cell receptors normally used for bacterial purposes Examples: sugar uptake, iron uptake, conjugation Virus takes advantage of host proteins 2. Injects genome through cell wall to cytoplasm Force of injection is very strong
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This note was uploaded on 08/04/2009 for the course BIOL 2051 taught by Professor Brininstool during the Fall '07 term at LSU.

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Chapter+6 - Chapter 6 Virus Structure and Function General...

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