Microbiology Chapter 5
Microbiology Chapter 5 Bio 221
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This 3 page Class Notes was uploaded by Savannah Carter on Monday September 19, 2016. The Class Notes belongs to Bio 221 at College of Western Idaho taught by Teresa Rich in Fall 2016. Since its upload, it has received 12 views. For similar materials see Microbiology in Biology at College of Western Idaho.
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Date Created: 09/19/16
Microbiology: Chapter 5 – Viral Structures and Life Cycles Position of Viruses in Biological Spectrum o What are Viruses? Filterable: filters designed to catch bacteria are not able to catch viruses Noncellular parasites Adapt over time Take over cells and reproduce with them o Virus Classification and Naming Host Nucleic Acid Composition Shape and Structure Genetic Relatedness General Structure of Viruses o Size Range Much smaller than cells Cells are measured in micrometers Viruses are measured in nanometers o Viral Components Capsids protein shell protecting the genetic material Spikes protein or glycoprotein that attaches to host cells Nucleic Acids either DNA or RNA Envelopes lipid bilayer stolen from the host cell (only some viruses) o Nucleic Acids DNA Double stranded Single stranded RNA Single stranded of positive polarity o Genome can act as an mRNA in the host cell o Ribosome can clamp on and start making proteins immediately Single stranded of negative polarity o mRNA copy must be made first Double stranded Retroviruses o RNA is converted to a double stranded DNA copy o DNA copy is inserted into the host cell’s DNA Viral Multiplication o Multiplication Cycles in Animal Viruses Step 1 absorption Step 2 penetration: getting viral genetic material into the cell If the virus is enveloped, viral envelope fuses with the cell membrane If the virus is naked, it will inject the material in By connecting with the cell receptor, it tricks the cell into letting it in Step 3 uncoating: getting rid of the capsid Step 4 synthesis: making copies of viral genetic information Process depends on configuration nucleotides Step 5 assembly and release Viral components are assembled Host cell might lyse – emptying viral contents Virus might exit the cell through the membrane o Damage to Host Cell and Persistent Infections Cytopathic Effect (CPE): physical changes to the host cell Viruses are identified by CPEs Persistent Infections Some cells produce viruses for years before it dies Some viruses enter a latent state in the cell and wait for an opportunity o Viruses and Cancer Oncogenic: viruses that permanently alter the cell’s genome, making it cancerous (transformation) Three Ways viruses cause cancer Promote uncontrolled cell growth o Viruses that Infect Bacteria Bacteriophages or Phages Limited in how they get in and out of the cell Must penetrate by injecting their genetic info Must release by lysing it o Lysogeny A latent infection Bacteriophage inserts its DNA into the bacteria’s DNA Hangs out as a prophage Prophage replicates every time the bacteria divides Some bring antibiotic resistance or toxins – helping the bacteria Lytic Phase Active phase for the virus Triggered by stress to the bacteria Virus quickly replicates and releases its copies before the cell dies Viral Cultivation o Purpose Isolate and identify viruses Prepare viruses for vaccines Do research on viral structure and effects on host cells o In Vivo: growing animal viruses in cells in a live animal Certain viruses will only infect certain host cells – must use the right animal Chicken embryos are used to grow influenza viruses for the yearly vaccines o In Vitro: growing animal viruses in cell cultures in a lab Require much less space and care than live animals and bird embryos Other Noncellular Infectious Agents o Satellite Viruses Defective viruses Lost the genes for capsid proteins or enzymes Must co-infect a cell with another virus – the healthy one provides what the satellite needs Makes the illness worse o Viroids Infect plants RNA genomes are very small Do not form capsids o Prions Misfolded neuro proteins Don’t perform proper functions Force functioning proteins into a misfolded shape Brain cells die Stable to heat, acid, and disinfectants (can’t kill them) Mad cow disease Viruses and Human Health o Effects Cause death and disability o Treatment Vaccines: boosts the immune system so it can defeat the virus Difficult to make o Must be tailor made to a specific step in the replication process of a specific virus o Side effects if you kill too many viral infected cells DRACO The first broad spectrum antiviral drug Stimulates any virally infected cell to self-destruct Needs to be cleared by the FDA Bacteria are easier to treat because they grow outside of cells
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