Microbiology

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Author:
dys1965
ID:
83742
Filename:
Microbiology
Updated:
2011-05-05 12:23:45
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Fundamentals Virology
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CH:10 Fundamentals of Virology
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  1. Adsorption:
    -The process by which molicules of a substance, such as a gas or liquid, collect on the surface of another substance, such as a solid. The molecules are attracted to the surface but do not enter the solids minute spaces as in absorption

    - Some drinking water filters consist of carbon cartridges that adsorb contaminants

    - Thi attachment process of key and lock fitting (attachment factor + receptor = adsorption)
  2. Attachment factor:
    - key
  3. Receptor:
    -correct lock
  4. bacteriophage:
    - bacterial virus

    - they cause a hole in a layer of bacteria by killing the bacteria
  5. capsid:
    Protein coat that wrapps a nucleic acid genome contained in a virus. (made of capsomeres)
  6. Capsomere:
    Protein sub-unit of cupsid (forms the coat around the viral nucleic acid)
  7. Carcinogenic:
    - Induce or generate cancer
  8. Cell Killing:
    - cells are killed by virus growth and observe a plaque (area w/no living cells), as a hole in the cell layer.
  9. Cytopathic effects:
    Refers to degenerative changes in cells, especially in tissue culture, and may be associated w/the multiplication of certain viruses.
  10. Enveloped virus:
    - The coat that a virus acquires as it exits a cell.
  11. Glycoprotein:
    - A protein covalently (share electrons) attached to a carbohydrate

    - Surface protein contained in a viron
  12. Host factory:
    - Suply the exzymes and building blocks energy necessary to propagate new virons
  13. Inclusion bodies:
    - Represent sites of viral multiplication in a bacterium or eukaryotic cell

    - microscopically observable dark areas of virus particles (accumulations!!)
  14. Leukemias:
    - Cancers in cells that freely move around normally occur in white blood cells (leuko:white)
  15. Lyse:
    - To cause dissolution or destruction of cells
  16. Lysogens:
    • - An agent capable of lysis
    • - A bacterial cell or strain that has been infected w/a temperate virus, one that does not cause cell destruction
  17. Naked virus:
    - A virus w/an enclosing envelope, consisting only of a nucleocapsid.
  18. Nucleocapsid:
    - The nucleic acid and surrounding protein coat of a virus
  19. Obligate intracellular parasites:
    - Can be maintained only inside living cells
  20. Plaque:
    - An area w/no living cells
  21. Proviruses:
    - Have potential to become lytic

    - also called lysogens

    - a form of evirus that is integrated into the genetic material of a host cell and by replicating with it can be transmitted from one cell generation to the next without causing lysis.
  22. Retrovirus:
    - Carry out transcription in reverse

    eg. HIV

    - the reading of RNA template to make DNA copy
  23. Reverse transcriptase:
    - Any class of enzyme that catalyze the formation of DNA from RNA template
  24. Round up:
    - When the host cells no longer adhere tightly to the bottom of the cx dish.
  25. Syncytia formation:
    - Virus cause cells to fuse together into giant cells
  26. Transformation:
    - Normal growth = single layer of cells

    - Tumor viruses cause cells to keep growing until piles of cells are visable

    - Same mechanism involved when cells of a tumor grow uncontrollably or metastasize.
  27. Tumor:
    Solid or tissue cancer
  28. Tumorigenesis:
    - Virus inducing turors
  29. virions:
    - Complete virus particles
  30. Virus:
    - Simplest organism on Earth

    - completely lack cellular structure and do not have a cytoplasmic membrane to determine inner or outer boundry of a cell.
  31. Virus particle:
    - Any virus w/its appropriate coating layers

    - also called a virion

    - Particle and viron are used to refer to the virus' physical structures because viruses are not cells
  32. Icosahedron:
    - 20 identical sides
  33. Because viruses are incapable of replicating outside of a host, they are called:
    - Obligate intracellular parasites
  34. What is the size of the largest virus:
    - 1/25th the size of the smallest bacterium
  35. What are bacterial viruses called:
    - bacteriophages or phages
  36. How does a bacteriophage penetrate the host cell wall:
    - They have a needle like tube to propel through the bacterial envelope and inject their nucleic acid inside the host cell
  37. 2 main components of nucleocapsids:
    - capsid

    - nucliec acid
  38. What are nonenveloped viruses called:
    - Naked virus
  39. The placement of viruses into families depends upon which characteristics:
    - general size and shape

    - naked or enveloped

    - is nucleic acid DNA or RNA
  40. What part of the envelope comes from the host cell and virus
    - The membrande is from the hose and attachment proteins are from virus
  41. What type of molecule in an enveloped virus is necessary for attachment to the host cell:
    - A viral attachment protein that protrudes outside of the viral envelope is necessary for attachment to athe host cell
  42. What are the 7 steps in the lifecycle of a human virus:
    • 1. Attachment
    • 2. Penetration
    • 3. Uncoating
    • 4. Nucleic acid replication
    • 5. Protein synthesis
    • 6. Self-assembly
    • 7. Release
  43. 1. Attachment:
    - also called adsorption

    - host cell receptor and viron attachment components are often related to a lock and key mechanism where the key (attachment factor) can only recognize the cell types that carry the correct lock (receptor).
  44. 2. Penetration:
    - Cell penetration by naked virus is mediated by endocytosis (virus tricks cell into taking it inside)

    - Membrane fusion; viron envelope fuses w/cell membrane to form a pore through which the nucleocapsid enters.
  45. 3. Uncoating:
    - Interalized nucleocapsid is uncoated by host enzymes, thus releasing the viral nucleic acid inside the cell.
  46. 4. Nucleic Acid Replication:
    - DNA viruses replicat in the host nucleus

    - RNA viruses replicate in the host cytoplasm

    - Tumor viruses turn on cell replication to continue dividing even when the host is trying to stop cell growth
  47. 5. Protein Synthesis:
    - Viruses use the host cell translational machinery in the host cytoplasm for protein synthesis.
  48. 6. Self-Assembly:
    - When proteins bind to other proteins, which results in components of virions pulling together (like a zipper) except no outside energy is required-the binding force provide energy.
  49. 7. Release:
    - Naked viruses escape by lysing the host cell

    - Enveloped viruses bud (push out) through the cell membrane (the membrane coating serves as its envelope)
  50. Adsorption of the virus to the cell depends upon what specific viral and cellualr components:
    - Adsorption depends on a viral attachment protein and cell receptor.
  51. What are the 2 types of penetration:
    1. endocytosis

    2. Membrane fusion
  52. Where and how does the process of uncoating take place:
    - Uncoating is the removal of the viral capsid protein by cellular enzymes in the cell cytoplasm
  53. Where does DNA and RNA replication take place:
    • - DNA: cell nucleus
    • - RNA: cell cytoplasm
  54. Where does viral translation occur:
    - In the host cytoplasm
  55. How does the assembly of intact virions occur:
    - Proteins from the coating bind to each other and to the proper nucleic acit, enabling the nucleacapsid to zip together without outside energy
  56. Describe how the release of virons can occur by cell lysis or budding:
    - A naked virus simply lyses the cell to release virons

    - An enveloped virus acquires a membrane from the host as it passes through the cell membrane
  57. How many phages or virions can be produced in a single growth cycle:
    - About 100 phages/bacterium

    - About 300,000 animal virons/animal cell in single growth cycle
  58. What are the differences between lytic and lysogenic viruses:
    - Lytic viruses always kill the host cell by breaking it open

    - Lysogenic viruses enter the cell where DNA integrates into the host cell and become part of it; they then divide w/the cell. If the host cell becomes sick, lysogenic viruses become lytic and escape the dying cell
  59. What are cytopathic effects:
    - result when a viral specimen is placed on human tissue in a cx medium

    - Cytopathic effect refers to visible changes, microscopic or otherwise, in cells resulting from viral infections
  60. What is plaque:
    - Specific type of CPE where cells are killed so that loss of cells gives rise to a hole in the cell layer
  61. How is the inclusion body type of CPE observed:
    - Inclusion bodies are normally seen in the microscope as dark areas of viral material
  62. What are the resulting large cells called when many cells fuse together as a result of viral infection:
    - Syncytia or giant cells
  63. What changes occur during transformation:
    - Viruses cause the cells to keep growing uncontrollably and pile up or form a tumor
  64. What do viruses do to the host DNA - synthesizing machenery:
    - Subvert the host cell machinery into making viruses rather than cellular materials
  65. What type of nucleic acid is in a virion:
    - RNA or DNA, but not both
  66. Why is tumorigenesis only assiciated with DNA viruses or retroviruses:
    - Only occurs when a cell's genes are altered to cause uncontrollable cell division. Only DNA can integrate into the cell's chromosome because the chromosome is DNA

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