Biology pathogens and disease

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  • Biology: Pathogens and Disease
    • Pathogens
      • Bacteria
        • Living cells that multiply rapidly
        • Release toxins into the body
        • e.g. food poisoning, cholera, typhoid and whooping cough
      • Viruses
        • Consist of genetic material in a protective protein coat.
        • Reproduce inside host cells
        • The virus expands until it splits the host cell so it is passed into the bloodstream
        • e.g. influenza, measles, mumps, chicken pox and AIDs
      • A pathogen is a disease causing pathogen
      • Pathogens spread by: air droplets, physical contact, food and drink, broken skin
    • Defence mechanisms
      • First line of defence
        • Skin and scabs provide a barrier
        • mucus traps pathogens
        • Stomach acid kills pathogens
      • Second line of defence
        • White blood cells ingest and destroy pathogens
      • Third line of defence
        • White blood cells release antibodies specific to antigens on the pathogen
          • Lymphocytes produce a specific antibody
          • when a lymphocyte meets the right antigen it reproduces quickly
        • They also release antitoxins to neutralise toxins
    • Vaccinations
      • inactive (weakened or dead) pathogen injected into the body
        • These stimulate white blood cells to produce antibodies
          • The right antibody is remembered so the body in future will know how to fight the disease
      • Protects a whole society from a disease
        • E.g. MMR
          • Mumps, measles and rubella
    • Antibiotics and medicine
      • Medicine relives symptoms
        • e.g. paracetamol, asprin and morphine
      • Antibiotics kill bacteria
        • Specific bacteria need specific antibiotics
        • Penicillin was fund by Alexander Fleming in 1928
      • Antibiotic resistance
        • Bacteria can develop resistance to antibiotics
          • Due to natural selection
      • Hygiene
        • Ignaz Semmelweiss insisted doctors washed their hands
          • It reduced the numbers of deaths from diseases in hospitals
    • Growing and investigating bacteria
      • Equipment: agar jelly, petri dish, inoculating loop, temperature of 25 degrees for safety
      • Sterilise the loop. Dip the loop into bacteria and zig-zag across the agar surface. Seal lid leaving space for air flow
      • sterilising is boiling solutions and heat treating apparatus to kill bacteria already on them
    • Epidemic and pandemic
      • Epidemic
        • rapid spread of infectious disease in one country
      • Pandemic
        • rapid spread of an infectious disease across many countries


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