Learning Objectives:After completing Chapter 1, students should be able to:•provide a definition of the term “virus,”•explain the basic structure of viruses (including genomes),•explain the central dogma of molecular biology.Chapter 1 - General Features of Virus Structure1
Chapter 1 - General Features of Virus StructureWhat are viruses?“Virus are tiny non-living agents with very complicated lives.”B. MarintchevaGenetic information (nucleic acid) surrounded by a protein coat.Some also contain external structures (e.g., spikes) and an envelope of phospholipids.Obligate intracellular parasites –i.e., they require host cells to reproduce.Each type of virus infects a specific unicellular species or cell type in a multi-cellular species.3
Chapter 1 - General Features of Virus StructureViruses are notcells.They cannotsynthesize their own ATP or amino acids or nucleotides.Cannotsynthesize proteins on their own.4VirusesExtracellular stateIntracellular stateInert particle(Protein, nucleic acid, maybe lipid)Replicating nucleic acids(Gene expression, viral proteins)
Chapter 1 - General Features of Virus Structure5VirusesCellsHereditary materialDNA or RNACan be single-stranded or double-strandedPlasma membrane presentNo (may have an envelope)YesCan carry out transcription independentlyYesCan carry out translation independentlyYesMetabolic capabilitiesExtensive - ATP synthesis, oxidation of reduced C, amino acid & nucleotide biosynthesis, etc.Characteristics of viruses vs. cells
Chapter 1 - General Features of Virus StructureCentral dogma of molecular biology – the flow of a genetic information withina biological system.Applies to all living cells. Applies to viruses too – sometimes with a twist.7
Chapter 1 - General Features of Virus StructureViruses are a diverse group of infectious agentsStructure (naked, enveloped, complex capsids).