Biology - Fighting Disease (AQA)
Vaccines cause the body to produce white blood cells to protect itself against one particular pathogen.

Biology - Fighting Disease (AQA)

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.

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.

Which of the following is not caused by bacteria or viruses?
Salmonella and listeria (food poisoning)
Cholera and typhoid
Whooping cough and sore throats
Scurvy and anaemia
Scurvy and anaemia are illnesses caused by a lack of certain vitamins and minerals in the body
Which of the following statements about the first ever antibiotic is true?
It is called pennysillyum and invented by Alexander Flaming
It is called penicillin and was discovered by accident by Alexander Fleming
It is called penicilliase and was made for use in the First World War
It is called amoxycillin and discovered by James Lister
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
How do antibiotics work?
They absorb the toxins released by the bacteria
They kill the viruses that have got into the body
They ingest the bacteria that are causing the infection
They stop the bacteria from reproducing
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
Antibiotics are effective against what?
Bacteria only
Viruses only
Both bacteria and viruses
Neither bacteria or viruses
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
Why do doctors think carefully about prescribing antibiotics?
Because they are expensive
Because they kill harmless viruses as well as pathogenic viruses
Because over use or patients who don't take the whole course can lead to the development of resistant bacteria
Because writing out a prescription for antibiotics is complicated and takes them a lot of time
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
Why do pathogenic diseases make you feel ill?
They alter all of the chemical reactions in your body
They slow down your metabolic rate
They produce toxins and can damage cells
It is because your immune system is fighting them off
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
What do vaccines contain?
Live pathogens but treated to make them harmless
Dead pathogens
Fragments of the pathogen that are harmless but which carry the antigen
Any of the above
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
What is a pathogen?
Someone who carries out post-mortems
A type of infectious disease
A microorganism that cause infectious diseases
A torch that surgeons wear on their heads during operations
Pathogens include bacteria, viruses, fungi and other single celled organisms
Before the 19th Century, why did doctors not wash their hands in between dealing with their patients?
They did not understand about infectious diseases
They were too lazy
Soap was not available
It meant that they could move on to the next patient as quickly as possible and make more money
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
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
You can find more about this topic by visiting BBC Bitesize - Infection and response

Author:  Kev Woodward

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