Biological basis of diseases

• Virus


  • Intracellular parasite that needs to use a host cell to reproduce
  • Not made of cells (acellular)
  • Lacks the metabolic machinery needed to acquire and use nutrients
• Viral genetic material


  • Need not be double-stranded DNA, or even DNA
  • Some viruses have RNA as their genetic material

  
• Virus structure


  • Outer capsid composed of protein units
  • Inner core of nucleic acids containing genetic information needed for viral reproduction

  
• Virus entry into host cell

  Spikes and proteins on virus surface are specific for a receptor on host cell's outer surface
• Virus life cycle


  1. Attachment

  2. Penetration

  3. Biosynthesis

  4. Maturation

  5. Release

  
• Epidemic


  More cases of a disease than expected in a certain area for a certain period of time
• Pandemic


  Global epidemic
• Examples of current pandemics: HIV/AIDS, SARS-CoV-2/COVID-19, tuberculosis, malaria, and influenza
• First human cases of HIV in the UK

  1959
• HIV structure


  • Two single strands of RNA
  • Various proteins
  • Envelope acquired from host cell
  • Reverse transcriptase, integrase, and protease enzymes

  
• HIV life cycle


  1. Attachment

  2. Fusion

  3. Entry

  4. Reverse transcription