Biology 40s - Viruses

  1. discovery of viruses (3)
    • viruses are smaller than living cells
    • can pass through filters
    • went undetected for a long time
  2. size of viruses (3)
    • size ranges from 20-400nm (nanometers)
    • can only be seen with an electron microscope
    • viruses can infect humans, animals, plants, and bacteria
  3. virus structure (3)
    • dna or rna
    • coat of protein
    • lipid membrane
  4. are viruses alive? (3)
    • no, they can only replicate in living cells (cannot reproduce on its own, must invade a host cell)
    • employ the host cell's replicate and metabolic pathways
    • referred to as "obligate intracellular parasites"
  5. virus diseases include
    • animals (rabies, foot and mouth disease)
    • humans (hepatitas, polio, influenza, AIDS, and SARS)
  6. types of viruses (7)
    • small pox¬†
    • polio
    • yellowfever
    • measles
    • mumps (swelling of salivary glands)
    • rabies (inflamed brain)
    • SARS
  7. describe protein synthesis (3)
    • living cells carry all the genetic info (DNA) they need to make copies of themselves stored in chromosomes
    • the DNA are copied into messenger RNA which are used to make the proteins that are needed for the structure of the cell
    • when cells divide they replicate each of their DNA to give two identical copies
  8. describe viral replication (2)
    • viruses carry a small amount of DNA, they use it to make a few special proteins which hijack the host cell and force it to make thousands of new viruses
    • all viruses have a protein that recognizes the proper host cell
  9. describe the lytic cycle (2)
    • the virus reproduces itself using the host cell's chemical machinery
    • virus injects its genetic material and tricks the cell into replicating
  10. describe the lysogenic cycle (6)
    • includes a dormant phase
    • once inside the host cell, some viruses like herpes and HIV do not reproduce right away
    • they mix their genetic instructions into the host cell's DNA, the viral info will reproduce with the cell
    • an environmental or genetic signal will stir the sleeping viral instructions
    • may be dormant for years
    • the cycle eventually reverts back to the lytic cycle
  11. can viruses be cured? (4)
    • immunizations (pre-infects the body with a weak or dead form of the virus to build antibodies)
    • antibiotics have no effect
    • deadly viruses include the ebola virus and west nile virus
    • vaccines work with with viruses with non-varying proteins (can' work when surface proteins mutate)
  12. the spread of a virus is influenced by 4 factors
    • size of the population of opportunity
    • number of days contagious
    • number of people with whom an infected person comes in contact¬†
    • probability of contracting the virus from contact with an infected person
  13. what ways do viruses spread
    • airborne
    • water
    • blood/bodily fluid contact
    • surfaces
  14. define epidemic
    a widespread outbreak of an infectious disease, many people are infected at the same time
  15. define pandemic
    an epidemic that is geographically widespread, occurring throughout a region or even throughout the world
  16. define endemic
    confined to a specific area
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Biology 40s - Viruses