Learning Target : Virus Anatomy and Physiology

Learning Target: Virus Anatomy and Physiology I Can… Explain how viruses infect host cells and manipulate the host cell into manufacturing more viruses. I Will… • Identify the fundamental structural components of a virus • List Characteristics of viruses • Describe two common ways viruses infect host cells • Describe the two types of viral infection pathways

Learning Target: Virus Anatomy and Physiology • Virus – Infectious particle made only of a nucleic acid strand (either DNA or RNA) surrounded by a protein coat • Nucleic acid • Single strand, double strand • Linear, circular or segmented • Protein coat – Capsid • Individual protein components • Different shapes • Some viruses have a lipid layer • Spikey surface protein and sugar structures • Used to attach to host cell • Can be used to identify the virus

Learning Target: Virus Anatomy and Physiology

Learning Target: Virus Anatomy and Physiology • Viruses • Do not have ribosomes • Cannot make enzymes • Cannot make proteins • Do not carry on metabolism • Inactive outside of the host cell • Unable to reproduce without host cell • Cannot copy DNA • Viruses are NOT alive

Learning Target: Virus Anatomy and Physiology • Virus shapes act lock-and-key • Can only infect certain cells • Spikes bind to cell membrane proteins • Usually species specific • e.g. Tobacco Mosaic Virus • Some viruses can cross between different species • e.g. H1N1 (Swine flu) • Some viruses start in birds • Mutate and pass to another species such as pigs • Mutate again and infect humans • Rabies virus infects all mammals

Learning Target: Virus Anatomy and Physiology Two common ways viruses infect host cells • Simple Injection • Virus attaches to cell surface • Injects nucleic acid into cell’s cytoplasm • Like a syringe • e.g. T-Bacteriophage • Endocytosis • Eukaryotic cells infected • Virus fuses with the cell membrane receptors • Releases capsid into cytoplasm in vesicle • e.g. HIV Continue

Learning Target: Virus Anatomy and Physiology • T-Bacteriophage infects E. coli bacteria • Simple injection method Return

Learning Target: Virus Anatomy and Physiology Viral RNA uses Reverse Transcriptase enzyme to make Viral DNA genes Return

Learning Target: Virus Anatomy and Physiology Once virus nucleic acid is inside host cell, 2 basic types of infection occurs • Lytic Cycle: • Virus nucleic acid takes control of host DNA • Turns on host genes to copy virus genes • Viral genes direct transcription and translation of proteins • Capsids • Enzymes • Enzymes help copy viral DNA • Host cell energy assembles viral parts • Viral enzymes dissolves host cell membrane • Destroys host cell and releases new viruses Lytic Cycle

Learning Target: Virus Anatomy and Physiology • Lysogenic Cycle: Virus combines its DNA into DNA of the host cell (Recombinant DNA) • Viral DNA genes inserted into host DNA • New set of genes • Prophage in bacteria • Provirus in other organisms • New genes may change cell traits • e.g. HPV link to cervical cancer • Cell goes through mitosis • Daughter cells get identical copies of new genes • Two Paths: • Dormant and continued passing through mitosis • Activated by stress trigger • Enters Lytic Cycle and destroys cell • e.g. Herpes viral cold sore

Learning Target: Virus Anatomy and Physiology Lytic Cycle or Lysogenic Cycle Return

Learning Target: Virus Anatomy and Physiology • Lytic Cycle • Virus is a “Bad house guest” • Moves in • Trashes the place • Blows up the house • Leaves for new house • Lysogenic Cycle • Virus moves in • Stays and does not leave • If stressed • Trashes the place • Blows up house and leaves for new house

Learning Check √: Virus Anatomy and Physiology • Name the two ways in which a virus (or virus’ DNA) can enter a cell: • __________________________ • __________________________ • What are the two viral infection cycle pathways? • _________________________ • _________________________ • 3. Why can’t you catch most viruses that infect plants or other animals.

Learning Target : Virus Anatomy and Physiology