Transcript Virus Notes
Viruses Objective: G2 - Describe viral structure, reproduction, & the role of viruses in causing diseases, and compare the structure of viruses to cells Virology - study of viruses Discovery of Viruses • Edward Jenner (1796) developed smallpox vaccine using milder cowpox viruses • Beijerinck (1897) coined the Latin name "virus" meaning poison • Wendell Stanley (1935) crystallized sap from tobacco leaves infected with a virus & found virus was made of nucleic acid & protein • Viruses couldn't be seen until the electron microscope was invented in the 1930s Viral Characteristics • Non living • Not made up of cells • Cannot grow or replicate on their own • Must be reproduced in living cells • Can ONLY reproduce inside of a living host cell • Some can cause disease (smallpox, measles, mononucleosis, influenza, colds, AIDS, Ebola) • Highly host specific (only infect certain cells) • Viruses are classified into 2 main groups by their nucleic acid --DNA or RNA Viruses Viral Structure • Consist of a nucleic acid core (DNA or RNA) and a protein coat called the capsid that allow them to identify a specific type of cell and attach to it • Lack ribosomes & enzymes needed for protein synthesis or metabolism Bacteriophage ---- – viruses that infect bacteria HIV ---------- - attacks T-cells of the human immune system Virus Replication ▪ Viruses cannot reproduce on their own, and must infect a host cell in order to create more viruses. Viruses use their own genetic material and the host cell's machinery ▪1. Penetration - surface proteins bind to host, and release genetic material (DNA or RNA) into the cytoplasm ▪2. Replication - the viral genetic material is copied ▪3. Transcription - the genetic material is used as a blueprint, for the cell to make messenger RNA which is used to make viral proteins ▪4. Protein synthesis - occurs in the cytoplasm (ribosomes), viral proteins are made ▪5. Viral Assembly - the viral genetic material (from replication) is surrounded by the newly made viral proteins ▪6. Release - viruses emerge from the cell by "budding" from the cell membrane or bursting out of the cell (this causes the cell's death) Lysogenic Cycle ▪ Lysogenic Pathway - the virus stays within the cell until certain environmental triggers cause it to enter the lytic cycle Lytic cycle ▪Lytic Pathway rapid replication of the virus, ending in cell lysis (or death). More viruses are released to infect other cells Human Immunodefiency Virus (HIV) - causes AIDS • Retrovirus - RNA inside a protein coat • HIV infects one particular type of immune system cell, called a T-helper cell that functions in the body’s immune response. • Once infected, the T-helper cell turns into a HIV-replicating cell. • There are typically 1 million Tcells per one milliliter of blood. HIV will slowly reduce the number of T-cells until the person develops AIDS. Check for Understanding NO !!! 1. Are viruses alive? _________ 2. Why or why not? Not made up of cells ________________________ 3. Can viruses reproduce on their own? No _______ 4. What do viruses need in order to reproduce? A host cell _________________________ 5. Structurally, what do viruses have in common with living things? Genetic information _________________ 6. What type of cell do bacteriophages bacteria attack? ________________ 7. Which body system do T-cells belong to? ________________ Immune