Lecture 17 - Biology of Viruses

Lecture 17 - Biology of Viruses - Lecture 17 - Biology of...

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Lecture 17 - Biology of Viruses Virus: - Obligate intracellular parasites tat infect host cells, multiply and spread o spread from cell to cell AND animal to animal - Lack the ability to generate ATP and to produce - Cannot produce their own structural components to carry out their metabolic needs (i.e. protein synthesis) o dependent on host for almost everything (DNA, RNA, protein synthesis) Unlike bacteria! Viruses are… - small - no gram stain (cannot be visualized by light microscope) - genetic economy: one DNA more than one protein more than one function (capsid assembled from multiple identical subunits) - mode of replication: infecting virion is disassembled progeny virions produced by separate synthesis and subsequent assembly of components o RNA splicing and Frame shift enable one segment of the virus genome to encode more than one vira protein - metabolism == host dependent o no mitrochondria or organelles (lack metabolic activity and have no intermediary metabolism) - viruses may specify unique enzymes (not provided by the host cell) o RNA polymerase – reverse transcriptase – can be present in the virions MI-38d. Describe the differences between viruses, viroids and prions - Viruses : DNA or RNA; structurally the simplest agents known to cause infections in humans - Viroids : small single-stranded RNA molecules; not know to cause disease - Prions : no nucleic acid genome MI-38a. Describe the structure of viruses and associate each structure with its function Structural units - basic protein building blocks of the coat Protomer - the individual unit of the structural units Subunit - single folded viral polypeptide chain Capsomeres - seen in electron microscope - represent clusters of polypeptides Defective virus - functionally deficient in some aspect replication Envelope - lipid membrane / glycoprotein spikes - acquired during viral maturation by budding process of host cellular membrane - Function : o attachment: virus to the host cell o fusion-mediated entry: fusion of virus envelope with host cell membrane (neutral pH)
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Lecture 17 - Biology of Viruses - Lecture 17 - Biology of...

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