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Flashcards in Virus Deck (17)
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Viruses History (1)


Explain Smallpox & Flu pandemics


  • caused by Variola
  • killed 300 million
  • changed many to christianity
  • From Europe (Conquistadores: Pizarro & Cortes)
  • expansion of afrian slaves bring yellow fever

Flu Pandemics

  • Mutation of flu
  • Influenza - described by Hipocrates. Antigenic shift:  major genetic change in H & N spike
  • Spanish Flu - killed 50 million ppl. Dropped life expectancy by 12 years



Viruses History (2)


Who issolated a tobacco virus?

Contagium vivum fluidum/contagious fluid

Wendell Stanley isolated tobacco virus for Chemcial & Structural composition




Descibe a virus

What does living organisms consists of?

Virus are inert outside a cell. Has no cellular life

  • Obligate intracellular parasite
  • Has DNA or RNA
  • Enclosed by envelope
  • has spikes (receptors determine what to infect)
  • most infects specific cells
  • Family:  Viridae (Retroviridae)
  • Genus:  Virus (Lentivirus)
  • Subspecies designated by a number i.e. (HIV-1)


Living organisms

  •     metabolic process
  •     homeostasis
  •     reproduction


Bacteriophages (Phages)

What is phage?


Define Phage Therapy

  • Viruses that infect bacteria. 
  • Receptor site is cell wall or Fimbraie or flagella


Potential candidate for disease treatment. Genetically manipulate to target specific cells i.e. tumors


Virus Hosts


How do viruses attach?

  • chemically interacts with a recptor site of host cell
  • Receptor site for Bacteriophage is cell wall or Fimbraie or flagella
  • Receptor site for Animal Virus is plasma membrane of host



Virion Structure


What does it consist of?

  • All has Nucleic acid:  DNA or RNA
  • All has capsid: Capsomeres, Protein subunits
  • Some has envelope:  Lipids, proteins & Carbs
  • Has Spikes: Glycoprotein used to attach host


Complex Viral Structure


Name the parts of the body

  • Typically bacteriophages
  • Capsid = head
  • Pin
  • Base plate
  • Tail Sheath
  • Tail fiber = spikes



Viral Multiplication


Describe process

  • Viral enzyemes concerned entirely with replicating or processing nucleic acid
  • Must invade a host cell
  • Hijacks host cells
  • Assembles and bursts our of the cell


Bacteriophage Multiplication


Describe the 2 types of multiplication process

2 types of multiplication

1) Lytic cycle:  ends with lysis and death of host cell.  Phage attaches by tail fiber

  • Penetration: Lysozyme opens cell wall and tail sheath contracts and forces tail fiber and DNA into host cell.
  • Biosynthesis:  Production of virus DNA and proteins
  • Maturation:  Assembles virus particles
  • Release:  Virus lysozyme breaks thru cell wall


2) Lysogenic cycle:  Ends with host cell remaining alive

  • Prophage:  inserted DNA (inactive)
  • Lysogenic cell: Incorporates virus DNA into bacteria host DNA
  • Sponaneous event or other stimulation occurs
  • Phage is activated and iniates Lytic cycle (Biosynthesis > Maturation > Release)






Lysogenic Cycle


What happens?

Immune to reinfection by same phage

Phage conversion:  exhibiting new properties, producing toxins

Specialized transduction: viruses transfering segments of DNA from one bacteria to another



Animal Virus Multiplication



Describe process


Whats different about poliovirus

Similar to bacteriophage multiplication except

Entire virus enters host cells (Pinocytosis)

Attaches to protein and glycoprotein of plasma membrane

Attachment site is found over the entire surface of virus

Enveloped virus enters host cell via Fusion

After infusion, capsid is released into host cytoplasm (HIV)


  • Attachment: virus attaches cell membrane
  • Penetration: via endocytosis or fusion
  • Uncoating:  by virus or host enzymes. It uncoats viral nucleic acid via lysosomal enzymes of the host.  (Except:  polio.  It uncoats itself during attachment).
  • Biosynthesis:  produces nucleic acid and proteins
  • Maturation:  Assembles nucleic acid and capsid proteins
  • Release:  via Budding (enveloped) or rupture (uneveloped)







Reverse Transcription




Synthesize RNA from DNA via RNA Polymerase using DNA template


Synthesize DNA from RNA via reverse transcriptase using RNA template


Synthesize Polypeptides from mRNA templates


Biosynthesis of DNA Virus

and types

DNA is synthesize in the nucleus

Viral capsid and proteins are synthesized in host cytoplasm then travels into the nucleus to assemble with the DNA

The complete virus is transported along the endoplasmic reticulum to the plasma membrane.

Attachment > Entry > uncoating > DNA released

Types - there are 2 types: single stranded and double stranded

Parvoviridae (Single)

Herpesviridae (Double)

Poxviridae (Double)

Papovaviridae (Double)



Biosynthesis of Single Stranded RNA Virus

Single stranded

Sense strand (+) acts as mRNA produce (-) antisense strand



Antisense strand (-) acts as template to produce sense (+) strand





The 2 compliments each other.

Then maturation and then released.




Biosynthesis of Double Stranded RNA Virus

Both anti sense and sense strand






RNA virus that makes double stranded DNA via reverse transcriptase.

RNA uses reverse transcriptase molecule to make a strand of DNA in the cytoplasm.

The single stranded DNA is reversed transcribed again to produce double stranded DNA in the cytoplasm.

The Double stranded DNA then moves into the nucleus and attaches to host chromosomes: PROVIRUS

RNA polymerase makes mRNA which makes other components of the virus such as the envelope and proteins.

Then buds off.

Protease then helps rearrange the virion to infect



Cancer/tumor producing