Biology - Fighting Disease (AQA Syllabus A)

In GCSE Science students will look at the requirements for staying healthy. This is the fifth of six quizzes on that topic and it looks specifically at fighting pathogens which cause disease, such as bacteria and viruses.

We have Ignaz Philipp Semmelweis to thank for modern standards of hygiene in our hospitals. He discovered that more women were dying in maternity wards manned by doctors than in those manned by midwives. He realised the difference was that the doctors performed post-mortems on women who died from a disease called 'childbed fever' but the midwives only delivered babies from healthy women. At the time, doctors didn't bother washing their hands so they were passing on the pathogens which cause infection to healthy patients.

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Semmelweis got his team to wash their hands between patients and after the post mortems, and this solved the problem. Even so, it took a while for the practice to become widely accepted in the medical profession. The problem was, they did not know that bacteria (and viruses) cause disease.

We now know and understand the causes of diseases and infections a lot better, and so we can help our bodies to defend themselves against harmful microorganisms. We have a wide range of antibiotics that help when fighting infections, and vaccines that reduce our chances of getting certain diseases in the first place.

But we have some problems fighting pathogens that mutate. MRSA is a strain of bacteria that is resistant to antibiotics and this creates a problem in our hospitals. Viruses that mutate can be deadly as we have little resistance to them. A bout of the 'flu is not pleasant but our bodies can ultimately deal with it, however, some strains of this virus, like H1N1 (bird 'flu) can become killers as our immune systems cannot cope with the mutated form.

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  1. What is a pathogen?
    Pathogens include bacteria, viruses, fungi and other single celled organisms
  2. Which of the following is not caused by bacteria or viruses?
    Scurvy and anaemia are illnesses caused by a lack of certain vitamins and minerals in the body
  3. Why do doctors think carefully about prescribing antibiotics?
    The use of antibiotics has prevented many deaths from infectious bacterial diseases. New antibiotics must be developed all the time to combat the new resistant bacteria
  4. What do vaccines contain?
    Whichever type of vaccine is used, it causes the body to produce white blood cells to protect itself against the particular pathogen targeted by the vaccination
  5. Which of the following types of drugs is most effective against a bacterial infection?
    Whilst painkillers help, they treat only the symptoms and not the cause
  6. Why do pathogenic diseases make you feel ill?
    Bacteria produce toxins (poisons). Viruses reproduce inside your cells and damage them as they escape to infect more cells. It is these poisons and the cell damage that cause the symptoms of infectious diseases
  7. Before the 19th Century, why did doctors not wash their hands in between dealing with their patients?
    Bacteria and viruses were only recognised as being the cause of infectious diseases in the second half of the 19th Century. Before that, doctors did not know that disease could be passed on via dirty hands
  8. How do antibiotics work?
    That is just one of the ways they work. Penicillin destroys the cell wall of the bacteria so they literally fall apart, other antibiotics affect the bacteria's DNA and others interfere with the chemical reactions that keep the bacteria alive
  9. Which of the following statements about the first ever antibiotic is true?
    Although Fleming discovered penicillin in 1928, he wasn't able to find anyone to help him make it. Two scientists, Florey and Chain, first produced it for testing on people in 1940 but it was several years later before a process for making it in large quantities had been found
  10. Antibiotics are effective against what?
    Antibiotics do not work against viruses because they reproduce inside cells. Any substance that destroys the virus would damage your cells too. When you have a viral infection like influenza, if your doctor prescribes antibiotics they are given to combat bacterial infections that may have arisen whilst your body is in a weakened state

Author: Kev Woodward

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