BSC1005 Unit 3 Viruses and Human Disease In Class Review 3 30 15 A micrometer 10 3 mm 10 8m A micrometer 1 micron A nanometer 10 3 micrometers 1 nanometer 10 angstroms Electron Microscopy o Uses electron beams instead of light o 100 times higher resolution can see interior structures of the cells and structure of viruses o Can only look at dead specimen because of vacuum requirement o Either transmitted or scanning o Specialty Cryo Em uses low temperate to preserve and tomography samples are rotated based on electron beams I Clicker Question o Which of the following does not belong in the group Viral Receptor Viral tropism Nucleic Acid Cell Surface CCR5 Virions binding to cell surface receptors o Membrane fusion at the cell surface pore formation at the cell surface o Through endocytosis membrane fusion in the endosome and pore formation in the endosome need the pH lower The DNA Double Helix double helix o A DNA molecule has two polynucleotides spiraling around an imaginary axis forming a o In the DNA double helix the two backbones run in opposite 5 to 3 directions from each other an arrangement referred to as antiparallel o The nitrogenous bases in DNA form hydrogen bonds in a complementary fashion A always with T U for RNA and G always with C o The three parts to a nucleotide base sugar phosphate Viral Genomes and replicative enzymes o DNA directed DNA polymerase uses DNA as template to make more copies of DNA o Reverse transcriptase use RNA as template to make DNA and then se resultant DNA as template to make more copies of the original RNA o RNA dependent RNA polymerase uses RNA as template to make more copies of RNA RdRps are not found in host cells they are only encoded by viral genomes o Low Fidelity vs High Fidelity RNA has a higher mutation rate because they are a lower fidelity Summary of Assembly o Expression of structural proteins late in replication o Structural proteins interact to form protein coat Pentamers of Hexamers o Packaging of viral genome packaging signal o Acquisition of envelope intracellular or plasma membrane o Exit from host cell cell lysis budding and exocytosis o Virion maturation cleavage by protease Icosahedron Three Modes of Virion Assembly o Is defined by 20 faces and symmetries of five fold three fold and two fold o Self Assembly capsid protein does it all by itself even without the genome Self assembled empty virus like particles can serve as vaccines ex HBV and HPV vaccines o Assisted Assembly chaperone proteins make sure the correct shapes such as pentamers and hexamers are formed ex Adenovirus o Assembly for Maturation I Clicker Question o Why do viruses need to use repeating units for building virions A The varied size of the virus B the need for the viral capsid to close C The size of the viral genome D the need for binding to cellular receptor Cell lines can grow forever and are easy to handle in labs but many are cancer cell lines and are limited The Virus host interactions o Primary cells versus cell lines o Endocytosis versus Exocytosis Viral entry versus viral exit o Transcription versus translation Normal functions of viral receptors o Signaling transmitting signal from outside of the cell to the inside of the cell o Adhesion allow cells to attach to surfaces o Cell junction formation sealing off space between cells o Uptake of extracellular nutrients Immunity Summary o Primary Barriers Skin Mucus Tears o Intrinsic cellular defense Interferons o Innate immunity Macrophages dendritic cells NK cells o Acquired immunity Immune memory and vaccines PAMPs and a PRRs o PAMP Pathogen associated molecular patterns o PRR Pattern recognition receptor host proteins that detect PAMPs and activate Membrane bound receptors toll like receptors TLRs dsRNA cellular responses The Death Pathways o Apoptosis Viral Diseases o Respiratory tract influenza o Gastrointestinal tract o Blood rotavirus HIV o Skin o Genital tract Zoonosis HIV and AIDS o Natural host animal reservoir o 35 million have HIV o 1 5 million died of HIV in 2013 o Transmission o Pathogenesis o Treatment o Prevention
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