Diseases and Fighting them

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How science Fights diseases


  • Once infected with a microorganism your WBC take a few days to learn how to deal with it
  • But by the time they do you can be very ill
  • A vaccination involves injecting small amounts of dead/inactive microorganisms
    • This causes the body to produce antibodies against the foreign bodies
      • E.g. MMR vaccine contains weakened virus versions of measles, mumps and rubella
  • After a vaccine the body already knows how to deal with a/some microorganisms if a live one infects you
    • This means they can rapidly produce antibodies from existing ones to attack and kill them off
  • Some vaccines wear off over time but booster injections can top them up by increasing the levels of antibodies again.
  • The speed at which the WBC can kill off the microorganisms gives them no time to damage cells too much or produce a serious amount of toxins.
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How science Fights diseases

  • Drugs
    • Some relieve systems while others cure the problem
      • Painkillers relieve pain they don't actually tackle the cause of the symptoms just reduce the symptoms
      • Antibiotics (Penicillin) actually kill or prevent the growth of bacteria without killing off body cells.
        • Different antibiotics are for different types of bacteria
        • They can't kill viruses though as viruses reproduce in your own body cells (their hosts) so drugs are hard to make that kill the virus not the body cell.
  • Resistant bacteria
    • Bacteria can mutate and somtimes these mutations cause them to become resistant to an antibiotic.
      • So being treated with antibiotics for these so calles 'superbugs' only kills the non-resistant bacteria. This increases the population of the resistant strain, a perfect example of natural slection. E.g. MRSA
      • The rate of development of resistant strains can be slowed by not over-prescribing antibiotics
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  • Viruses and Bacteria are the 2 main types of Pathogen
    • Bacteria are very small living cells=1/100th of a normal body cell)
    • Bacteria can reproduce quickly in your body
    • They make you feel ill by damaging your cells and producing toxins.
    • Viruses aren't cells and they're much smaller (circa 1/100th of a bacterium)
    • They invade your cells and replicate themselves using the cell's machinary to produce numerous copies of themselves
    • The cell eventully bursts releasing the copies
    • The cell damage makes you feel ill
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Defence System in the body

  • Skin, hairs and mucus in your respiratory tract stop a lot of Pathogens getting inside your body
  • Cuts=entry point for Pathogens=platelets in the blood (small fragments of cells) help clot the blood quickly sealing entry points.
  • Less platelets=slower blood clotting
  • If something gets through uter defences the immune system kicks in.
    • IMPORTANT=White blood cells. they traverse the body patrolling for microbes constantly.
      • When they find a microbe they attack three ways
        • Consuming-engulfing foreign bodies and digesting them.
        • Abtibodies-every invading cell has unique molecules called antigens on their surface
        • A foreign antigen=production of proteins called antibodies
          • These lock onto and kill invading cells
          • Antibodies are specific to the type of antigen
        • Antitoxins-produced to counteract toxins produced by invading bacteria
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How science Fights diseases

Investigating Antibiotics

  • Grown cultures of microorganisms can be used to test drug effectiveness
    • They're grown in a culture medium like agar jelly which contains the carbs, minerals, proteins and vitamins they need for growth.
    • Hot agar jelly gets poured into petri dishes, cools and sets
    • Inoculating loops (metal wire loops) are sterilised and used to transfer microorganisms to the agar jelly (culture medium). Here the microorganisms reproduce and grow.
    • Paper discs soaked in different antibiotics are then placed on the jelly. Antibiotic resistant strains will continue to multiply while the non-resistant will be killed off.
    • Petri dishes, Inoc. loops and culture medium must be sterilised before use. Inoc. loops get passed through a (bunsen burner) flame.
      • Unwanted organisms could get onto the culture medium without sterilisation and mutiply.Affecting the result.
    • Petri dish also needs a lid stopping any air-borne microorganisms contaminating the culture.
      • This should be taped in place/secured somehow.
    • In a lab at school cultures are kept at 25C. Harmful Pathogens likely won't grow at this.
    • In industrial conditions cultures are incubated at higher temps. These grow faster.
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New and Scary Dangers


  • They can mutate to produce new strains
  • New strains can be antibiotic resistant and so infections would no longer be cleared by current treatments.
  • OR a new strain could an unencountered one so no-one would be immune to it.
  • Thus a new strain of bacteria could spread rapidly and cause an epidemic.


  • Viruses also often mutate making it hard to develop a vaccine that will work for a length of time because changes to their DNA can make their antigens different and so unrecognisable.
  • A virus evolving that is both deadly and very infectious=a real problem
    • If this happens precautions could be taken to stop the virus spreading in the first place (quarantine) and vaccines and antiviral drugs could be developed (however it would take a while to get them mass produced.
  • In the worst case scenario a Flu Pandemic could cause billions to die all over the world.
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How science Fights diseases

Pros of Vaccination

  • Vaccines have helped control lots of infectious diseases that were once common in the UK. Smallpox now never occurs and Polio infections have fallen by 99%.
  • Herd immunity=vaccines prevent large outbreaks of disease if a large % of the population is vaccinated.
    • This way fewer people will catch the disease (even if not vaccinated) as there are fewer people to pas it on.


  • Vaccines don't always work-sometimes they don't provide immunity
  • People sometimes have bad reactions to vaccines but these are very rare e.g. swelling, or sometimes fever/seizures.
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Past of Fighting Diseases


  • Used Antiseptics
  • Working in Vienna Hospital in the 1840s he noticed women dieing in huge numbers after childbirth from puerperal fever.
  • He believed doctors were spreading diseases through unwashed hands.
  • He cut the death rate by 10% (from 12 to 2).
    • He did this by getting doctors to wash their hands in an antiseptic solution before entering his ward.
      • The antiseptic solution killed bacteria on their hands but no-one knew of the existence of bacteria and how they caused diseases for another 20 years.
      • Since he couldn't prove why/how his idea worked it was dropped when he left so death rates rose again.
  • Now we know basic hygeine is essential to controlling the spread of diseases (though recent reports have found that lack of it in oe hospitals has helped spread MRSA)
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Future of Fighting Diseases

Antibiotic Resistance

    • It's becoming more common
    • For the last few decades we could deal with bacterial infections with antibiotics so the death rate from infectious diseases geatly decreased.
    • Overuse of antibiotics has made the problem of antibiotic resistant strains of bacteria even worse by increasing the probability of someone being infected by an anticiotic resistant strain.
  • People infected with these strains can't easily get rid of them so may pass on the infection to others.
  • So antibiotic resistance=a big problem=drug companies beginning to work on finding an alternative to antibiotics that's effective against these strains.
  • Meanwhile 'superbugs' (resistant strains) are becoming more common.
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