Microbio final Pt 1

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  1. Are viruses living entities?
    • Once viruses enter hosts, their nucleic acids become active and can multiply; only alive when inside host
    • From a clinical POV, they are alive because they infect and cause disease
    • They are obligatory intracellular parasites—they absolutely require living hosts cells to multipy
  2. What are the true biological purposes of viruses?
    symbiosis: give host a benefit

    population control: keeps population at a good number

    carbon and itrogen cycle
  3. Viruses are entities that:
    - DNA? 
    - surrounding?
    - multiply?

    Viruses cause __

    Viruses lack?
    - contain a single type of NA, either DNA or RNA

    - contain a protein coat that surrounds the NA

    - multiply inside living cells by using the cell's machinery

    cause the synthesis of specialized structures that can transfer the viral nucleic acid to other cells

    viruses lack enzymes for protein synthesis and ATP generation; they must take over the host cell machinery
  4. Virus’ host range is determined by __

    For infection, the outer surface of the virus must do what?; held together by __--->  strong association between __ and __
    For some phages, the receptor site is where; others have it in __
    the virus’ requirements for its specific attachment to the host cell and the availability within the potential host of cellular factors required for viral multiplication

    chemically interact with specific receptor sites on the surface of the cell

    H bonds

    host cell and virus

    part of the cell wall of the host

  5. Host range size
    some are small; others are large
  6. Structural elements of the virus.
    • NA
    • Capsid: protomer and capsomere
    • nucleocapsid
    • envelope
    • virion
  7. NA:
    either DNA or RNA; can be ss or ds; linear or circular; in some viruses, the NA is in several separate segments
  8. Capsid
    protein coat; structure determined by NA and houses genetic material

    • protomer: individual proteins of capsid
    • capsomere: protein subunits that make the capsid; can be of a single type or a variety; 3 protomer structure "legos" making up a capsid
  9. nucleocapsid
    genetic material in capsid
  10. envelope
    some have small membrane taken from host; "bag" aaround virus
  11. virion
    a complete, fully developed, infectious viral particle compoused of NA and surrounded by a protein coat outside host cell
  12. Viral Envelope

    In some, the capsid is covered by __with combo of __, __, and __; sometimes the coat can be of the __; it then becomes the __, which contains materials derived from host

    Envelopes can be covered by __, which are __; allow __ and __

    When enveloped, they are called __
    • envelope 
    • lipids, proteins, and carbs
    • host cell membrane
    • viral envelope
    • spikes
    • carb-protein compexes that project from the surface of the envelope
    • attachment to host and identification
    • enveloped helical or enveloped polyhedral viruses
  13. Absence of Viral Envelope

    Nonenveloped viruses: Capsid does what and allows what?
    Typically, what happens after infection and what should happen?
    some viruses escape this due to __
    protects the NA from nucleases and allows attachment

    • antibodies are produced against virus; it should inactivate the virus
    • mutation of the genes that code for the surface protein
  14. Why is it hard to make antiviral drugs? 
    The __ is the spectrum of host cells the virus can infect. They can infect specific types of cells of only one host species.
    In rare cases, they __.
    Viruses that infect bacteria—__
    most drugs that would interfere with viral multiplication would interfere with host cell

    host range

    • cross the host-range barrier, expanding their host range
    • bacteriophages
  15. Oncolytic viruses are __
    tumor destroying viruses
  16. What are the morphologies?
    icosahedral (polyhedral)


    complex (phages)
  17. Icosahedral 
    - faces and corners
    - capsomeres
    - naked or enveloped?
    - what can be present?
    • 20 triangular faces and 12 corners
    • capsomeres of each face form an equilateral triangle
    • naked or enveloped (when enveloped, roughly sphercal)

    • envelope: mini representation of what membrane of host looked like when virus left host
    • spike proteins: attachment honing entry into host cell; helps get new virus out of host cell
  18. Helical
    long rods that may be rigid or flexible
  19. Complex:
    • bacteriophage: polyhedral head and helical tail sheath
    • the head houses the NA
  20. What is the mechanism of bacteriophages?
    • landing
    • pinning
    • tail contraction and penetration
    • DNA injection
  21. Growing bacteriophages
    - plaque method
    - some can be grown and studied through __
    - others can be injected into __
    - __
    Sample of phage mixed with host bacteria and agar; poured into Petri plate; virus infect bacteria, creating clearings, called plaques

    living animals by studying immune response of aminal

    Embryonated eggs: study death, damage, or lesions of embryo

    Cell cultures
  22. Multiplication of Phages

    NA contains only a few of the genes needed for __, including genes for __ and the few __

    Synthesized and functional only within __

    Viral enzymes only concerned with __; enzymes needed for other tasks, like protein synthesis, are supplied by __

    To multiply, it must __
    • synthesis of new viruses
    • structural components
    • enzymes of the life cycle
    • host
    • replicating NA
    • host cell
    • invade a host and take over the cell’s machinery
  23. Lytic Cycle
    • Attaches to host and injects DNA; penetration
    • Phage DNA forms a circle
    • Circle multiplies and is transcribed
    • Production of new phage and cell lysis, releasing phage virions
  24. Lysogenic Cycle
    • Attaches to host and injects DNA; penetration
    • Phage DNA forms a circle
    • Circle recombines with and becomes part of circular bacterial DNA= prophage (genes arerepressed by two repressor proteins that are the products of phage genes= stop transcription
    • Prophage DNA gets replicated with host; but, it is latent
    • Activation of lytic phase caused by stress
  25. What are the three important aspects of the lysogenic cycle?
    • Lysogenic cells are immune to reinfection by same phage
    • Phage conversion=host cell may exhibit new properties
    • Specialized transduction is possible; only certain bacterial genes can be transferred
  26. Enveloped viruses get into the cell how?
    attachment to host cell receptors

    fusion with the membrane
  27. Naked Virus method of entry
    Direct penetration:: Cuts edge of host cytoplasmic membrane and injects DNA

    they can enter through receptor mediated endocytosis
  28. Animal Viruses differ how from bacteriophages
    in their entry

    animal viruses also have certain types of enzymes not found in phages

    mechanisms of mature and release, and effects of host cell, differ from phages
  29. Attachment

    Attachment sites complementary to __
    These receptor sites are __
    Attachment sites are distributed over the __
    Receptor sites are __
    Receptor can vary from __
    • receptor sites on host
    • proteins and glycoproteins
    • surface of the virus
    • inherited characteristics of the host
    • person to person
  30. Entry

    Many viruses enter by __
    __form and have elements that originate from outside the cell, such as a __
    Enveloped viruses can also enter by __, in which __
    • receptor-mediated endocytosis
    • Vesicles 
    • virion
    • fusion
    • viral envelope fuses with plasma membrane and releases capsid into cell’s cytoplasm
  31. Uncoating is __

    What happens to the capsid?
    the separation of viral NA from its protein coat once the virion is enclosed within the vesicle 

    digested when cell attempts to digest vesicle's contents
  32. Biosynthesis of DNA viruses

    DNA-containing viruses replicate their DNA in the nucleus of the host cell by using __, and they synthesize their capsid and other proteins in the cytoplasm by using __. The proteins __ and __, which are transported __to the host cell’s membrane for release
    • viral enzymes
    • host cell enzymes
    • migrate into the nucleus
    • are joined with newly synthesized DNA to form vrions
    • along the ER
  33. Example of multiplication of DNA virus
    Attachment-->entry-->uncoating--> viral DNA released into nucleus of host cell

    Transcription and translation--> enzymes required for multiplication of viral DNA (can be carried out by transcriptase); early genes first, then late genes, which include capsid and structural proteins

    Synthesis of capsid proteins, which migrate into nucleus of host cell, mature, and form complete viruses-->release
  34. Biosynthesis of RNA viruses

    + ssRNA
    • RNA viruses multiply in host cell’s cytoplasm
    • After uncoating, ssRNA viruses with + strand genome can synthesize proteins directly from + strand. Using + strand as template, they transcribe – strands to produce more + strands to serve as mRNA and be incorporated into capsid proteins as the viral genome
  35. Biosynthesis of RNA viruses

    - ssRNA
    ssRNA viruses with – strand genome must transcribe a + strand to serve as mRNA before synthesizing proteins. The mRNA transcribes additional – strands for incorporation into capsid protein
  36. + ssRNA= __strand

    Can act as __

    After attaching, penetrating, and uncoating, the single-stranded viral RNA is __, which do what, and which form an enzyme called __. This enzyme catalyzes the synthesis of another strand of RNA, which is complementary in base sequence to the original infecting strand. This new strand, called an __ serves as a __ for __.
    • Sense 
    • mRNA
    • translated into two principal proteins
    • inhibit the host cell’s synthesis of RNA and protein
    • RNA-dependent RNA polymerase
    • antisense strand (- strand)
    • template to produce additional + strands
    • mRNA 
    • incorporated into capsid proteins to form a new virus
  37. The + strands may do three things. What are they? 

    Once viral RNA and protein are synthesized, __ occurs.
    1) may serve as mRNA for the translation of capsid proteins

    2) may become incorporated into capsid proteins to form a new virus

    3) may serve as a template for continued RNA multiplication. 

  38. The formation of mRNA and RNA for new retrovirus virions may carry __, which uses the __ as a template to produce __. This enzyme also __.
    Viral DNA is then integrated into host cell chromosome as __, which never comes out of the chromosome (as prophage does)
    Sometimes the __can remain __; or, it can __
    • reverse transcriptase
    • viral RNA
    • complementary dsDNA
    • degrades the original viral RNA
    • provirus
    • provirus 
    • latent
    • produce new viruses
  39. Maturation and Release

    First step in maturation: __  

    __ of animal viruses enclosed by envelope consisting of __, __, and __

    Envelope protein encoded by __ and incorporated into __; __ and __ are encoded by host
    Envelope develops by __--> pushes through membrane, which envelopes the virus
    Nonenveloped viruses are released through __
    • assembly of protein capsid; spontaneous
    • Capsids
    • protein, lipid, and carb
    • viral gene
    • plasma membrane of host
    • lipid and carb
    • budding
    • ruptures in the host cell plasma membrane
  40. Standard Classification Criteria
    • Nucleic Acid
    • Size and Morphology
    • Enzymes
    • Susceptibility to Physical and Chemical Agents
    • Immunologic Properties
    • Methods of Transmission
    • Host, Tissue and Trophism
    • Pathology
    • Symptomatology
  41. Class I
    dsDNA viruses (e.g. Adenoviruses, Herpesviruses, Poxviruses)
  42. Class II
    ssDNA viruses (+ strand or "sense") DNA (e.g. Parvoviruses)
  43. Class III
    dsRNA viruses (e.g. Reoviruses)
  44. Class IV
    (+)ssRNA viruses (+ strand or sense) RNA (e.g. Picornaviruses, Togaviruses
  45. Class V
    (−)ssRNA viruses (− strand or antisense) RNA (e.g. Orthomyxoviruses, Rhabdoviruses)
  46. Class VI
    ssRNA-RT viruses (+ strand or sense) RNA with DNA intermediate in life-cycle (e.g. Retroviruses)
  47. Class VII
    dsDNA-RT viruses (e.g. Hepadnaviruses
  48. Taxonomy
    • Family (suffix –viridae)
    • Subfamily (suffix – nae)
    • Genus (suffix - virus)
    • Species
    • Type (Serotype)
    • Strain
Card Set:
Microbio final Pt 1
2014-11-26 16:29:08
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