GCSE BIOLOGY REVISION: INFECTION AND RESPONSE
Please note: Text in bold is what the AQA GCSE biology specification requires an understanding of.
Students should be able to explain how vaccination will prevent illness in an individual, and how the spread of pathogens can be reduced by immunising a large proportion of the population.
Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies. If the same pathogen re-enters the body the white blood cells respond quickly to produce the correct antibodies, preventing infection.
Students do not need to know details of vaccination schedules and side effects associated with specific vaccines.
A vaccine is treatment used to produce immunity against a disease. They contain dead or altered forms of microbes. These microbes would normally be pathogenic, however due to them being inactive or altered, they cannot cause disease, but they can activate immune system cells. This is because the microbe will still have its antigens, therefore, white blood cells will produce complementary antibodies. Phagocytosis occurs (where the white blood cell engulfs the pathogen), and the white blood cell then presents the pathogens antigens on its outer surface to activate more immune system cells.
The primary infection is what we call the first exposure to the pathogen. During primary infection, the number of antibodies will gradually increase until it reaches a peak after roughly 10 days. Secondary infection (second exposure) will lead to a quicker production of antibodies as white blood cells have memory of prior infection and can produce the correct antibodies more efficiently.
Antibiotics and painkillers
Students should be able to explain the use of antibiotics and other medicines in treating disease. Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body. It is important that specific bacteria should be treated by specific antibiotics.
The use of antibiotics has greatly reduced deaths from infectious bacterial diseases. However, the emergence of strains resistant to antibiotics is of great concern.
Antibiotics cannot kill viral pathogens. Painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens. It is difficult to develop drugs that kill viruses without also damaging the body’s tissues.
Different medicines are used to treat different diseases, some are used to treat the symptoms of a disease whilst others are used to cure it by killing pathogens.
These are chemicals that relieve the symptoms. Painkillers do not cure what is causing the pain. Examples of painkillers are paracetamol and aspirin. Whilst they work to relieve the pain, your immune system cells will be working to fight the pathogen.
These are substances that slow or inhibit the growth of bacteria. They are highly specific and should not be oversubscribed as this increases the risk of antibiotic resistance. A common example is penicillin. They can only be used to treat bacterial infection, not viral infection. If you would like to know, it is discussed in a previous article.