Chapter 6

Chapter 6 - Chapter 6- Virus Structure and Function *highly...

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Chapter 6- Virus Structure and Function *highly recommended that you read this chapter General Properties of Viruses (virions) _obligate intracellular parasite ___ made of nucleic acid surrounded by a protein coat. Only replicate inside the host cell No nucleus, organelles, cytoplasm, no nucleoid 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 _Icosahedral ___ capsids Roughly spherical 20 equilateral Many animal viruses have this filamentous___ _ capsids Long ____tube of protein ______, with genome inside Tube made up of 100s of identical protein subunits Tube length reflects size of viral genome Ex: tobacco mosaic virus __complex ____ capsids Many bacteriophage (viruses that infect bacteria) ___asymmetrical (irregular)______ shapes Tend to be larger viruses
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Poxviruses Virus Structure—Envelopes Envelope- lipid bilayer around capsid of some viruses (typically animal viruses- the ones that affect us) 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 (attach specifically to some type of receptor protein, must be something host cell has outside of its membrane) 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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3. Replicate genome- lytic vs. lysogenic phage
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Chapter 6 - Chapter 6- Virus Structure and Function *highly...

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