Defending ourselves against infectious disease

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  • Defending ourselves against infectious disease
    • Pathogens
      • Micro-organisms that cause infectious diseases
      • Viruses, Bacteria, Protoctists, Fungi
      • Parasites that live in or on the body of a host and causes harm
        • Reproduce rapidly 1 per 20mins - bacteria
        • Invade and destroy host cells
        • Secretion of toxins/ poisons
    • Viruses
      • Smaller than bacteria
      • Make more viruses inside host cell- burst out
      • DNA and protein coat
    • Bacteria
      • Smaller than plant and animal cells
      • Cytoplasm, membrane, wall, genes in plasmids
      • Need: nutrients, oxygen, warmth and water
        • Body is ideal so multiply rapidly- binary fission
    • Growing microbes
      • Culture medium must contain: Carbs, mineral ions
      • Aseptic techniques
      • Heat glassware to 100c to sterilise
    • Spread of disease
      • Droplet infection: when you are ill you expel tiny droplets full of pathogens- sneezing
      • Contam. food and drink: raw or undercook, unpure water- diarrhoea, salmonella
        • Microbes go straight to the gut
      • Break in skin: HIV/Aids can enter through cuts or scratches
      • Direct contact: genital herpes spread by contact of skin
    • Defence
      • Barriers, phagocytes, specific immune responses
      • Clotting forms scabs and stops pathogens entering
      • Cilia & muscus line respiratory passages, pathogens stick to them
      • Stomach produce HCL acid
      • Phagocytes (wbc) engulf and ingest pathogens
      • Lymphocytes produce antibodies for the anigens
    • Vaccination
      • Inject a modified toxin
      • Injecting a modified live bacteria or virus
      • Injecting dead bacteria or virus
      • Injecting parts of antigens which act as antigens
    • Bacterial Mutations
      • A change in the DNA of an organism
      • If mutated are resistant to antibiotics
      • Antibiotics cannot kill viruses
      • Natural selection- evolution, the fittest survive, breed and pass on the useful characteristic


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