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Virus Structure and Method of Invasion. Higher Biology. Introduction to viruses. Obligate parasites Specific to type of cells they target - poliomylelitis virus attacks nerve cells - hepatitis virus attacks liver cells Reproduction is their only true characteristic of being alive

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Presentation Transcript
introduction to viruses
Introduction to viruses
  • Obligate parasites
  • Specific to type of cells they target

-poliomylelitis virus attacks nerve cells

-hepatitis virus attacks liver cells

  • Reproduction is their only true characteristic of being alive
  • Much smaller than bacteria (20-300nm)
viral structure
Viral Structure
  • Not a cell!
  • DNA or RNA (retrovirus)
  • Surrounded by protective protein coat (capsid)
  • Genetic material carries information for multiplication
  • Hijacks biochemical machinery of host cell to carry these processes out
invasion of a cell by a virus
Invasion of a cell by a virus
  • Virus can lie dormant for many years until it comes into contact with a suitable host cell
  • Binds with molecules on surface of host cell
  • Herpes

-whole virus enters cell

  • Bacteriophage

-viral DNA injected via hollow tail

alteration of cell instruction
Alteration of Cell Instruction
  • Virus takes control of cell machinery
  • Depends on host for

-ATP

-supply of free nucleotides

  • Virus suppresses cell’s normal nucleic acid replication and protein synthesis
  • Manufactures many identical copies of viral nucleic acid and protein coats
slide7
New viral particles become assembled and become released by:
  • Lysis

-viral nucleic acid used to synthesise lysis enzymes

-bursting of host cell to release viral particles

OR

2. Buds contaning virus are formed

retrovirus
Retrovirus
  • Contains RNA
  • No DNA to transcribe into mRNA
  • Reverse transcriptase injected into cell by virus with RNA

-enzyme reverses normal transcription

-Produces viral DNA from RNA

-Virus uses DNA to replicate

some video clips
Some video clips
  • Bacteriophage entering a cell
  • HIV replication
slide11

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