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Microbiology Exam Guide 2.docx

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Microbiology Exam Guide 2 Viruses and Virology  Viruses o Virus-small infection agent, replicates only in living cells (hosts)  Can only infect specific hosts  Highly specific  Can i... nfect all types of cells  Some can infect other viruses o Virion-virus particle that is an extracellular form  Outside the cell  Has nucleic acid genome, surrounded by protein coat  Might have an extra lipid layer, has lots of receptors on the outside  Able to infect  Morphology of Virion o Smaller than bacteria o Only have nucleic acids with a protein coat/capsid o Icosahedral viruses-spherical  20-300 nm  Symmetry  Form a closed shell  Might have sharp visible edges  Can be enveloped viruses-have a membrane that surrounds the nucleocapsid  Lipid bilayer with embedded proteins or lipid monolayer  Envelope makes initial contact with the host cell o Helical viruses-tube/rod like  Capsid proteins on outside with RNA in cylindrical shape  Length depends on the length of the nucleic acid  Width is determined by size of packaging or protein subunits (capsomeres) o Complex viruses-bacteriophages  Have a head, tail, and collar (connects head and tail)  DNA only in the head, rest is protein  Tail helps inject DNA into other cells o Capsid-protein shell that surrounds the genome of a virus  Made of protein molecules arranged in a highly repetitive pattern around the nucleic acid  Capsomere-subunit of capsid  Smallest morphological unit, can see with electron microscope  Nucleocapsid-complex of nucleic acid and protein packed into the virion [Show More]

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