Bio mod 7 w1

• Pathogen


  Any organism or infective agent that lives in or on another living organism that causes a disease
• Pathogens


  • Prions
  • Viruses
  • Bacteria
  • Protozoans
  • Fungi
  • Macro-parasites
• Prions


  • Disease causing proteins with no DNA/RNA
  • Normal prion proteins are in the nerve cells in the brain and do not cause disease
  • A mutation in the prion protein gene results in a disease-causing form of the protein that is resistant to heat and chemicals
  • Infectious prions stick together and form long fibres which are toxic to nerve cells
  • Nerve cells die and form holes in the brain, leading to spongiform disease
  • Infectious prions multiply by changing the structure of the normal prion proteins into infectious prion proteins
• Ways disease can be contracted from prions


  • Eating the diseased brain tissue
  • Contamination during medical procedure
  • Inheriting mutated gene
  • Spontaneous formation of infectious prion protein
• Prion diseases


  • Kuru - found in tribes in PNG, contracted through eating brains of dead relative, symptoms of uncontrolled shaking of face
  • Creutzfeldt-Jakob disease (CJD) - problems with muscular coordination, personality changes, dementia, involuntary muscle jerks, patients lapse into coma before death
  • vCJD (form of CJD) - contracted by eating beef from cattle infected with bovine spongiform encephalopathy (BSE)
• Viruses


  • Non-cellular organisms
  • Consist of a protein coat, DNA, RNA (can reverse transcriptase DNA → RNA vice versa)
  • Need a host to replicate
  • Attach to host surface, invade and make copies of itself
  • Bacteriophages are type of virus that infect bacteria
  • Infect by injecting genetic material into host cell
• Viral pathogens


  • Influenza, AIDS, Herpes, Zika, Measles, COVID
  • Viroids are smaller and less complex circular RNA only infect plants
• Prions vs Viral pathogens


  Prion is an abnormally folded disease causing protein that contains no DNA/RNA, while a viral pathogen is non-cellular and consists of a protein coat with DNA and RNA. Viruses need a host to replicate, while prions do not need a host to replicate, they replicate themselves. Both are pathogens that cause diseases.
• Bacteria


  • Single-celled prokaryotic organisms
  • Reproduce by binary fission
  • Can be beneficial or harmful
• Bacterial pathogens


  • Tetanus (Clostridium tetani), Food poisoning (Salmonella)
• Protozoans


  • Single-celled eukaryotic organisms with cell membrane and organelles
  • Types: Flagellates (have a whip-like tail called flagellum), Ciliates (covered in tiny hairs called cilia to help them move), Pseudopodia (project a 'foot' to move around), Sporozoa (reproduce by spores)
• Protozoan pathogens


  • Malaria (plasmodium through mosquito vector), Trypanosomiasis (African Sleeping sickness), Amoebic Dysentery
• Fungi


  • Eukaryotic organisms with a cell wall
  • Unicellular (yeast) or Multicellular (mushroom)
  • Reproduce sexually and asexually
  • Most fungal pathogens are dermatophytes, meaning they live on skin, nails and hair
• Fungal pathogens


  • Thrush, Athlete's foot
• Macroparasites


  • Parasites that are visible to the naked eye
  • Multicellular
  • Endoparasites (live inside host's body, e.g. tapeworms)
  • Ectoparasites (live outside host's body, can inject toxins or act as vectors, e.g. lice)