AQA GCSE Biology

Revision Notes

3.1.8 Antibiotics & Painkillers

Antibiotics & Painkillers

  • When treating a disease there are two types of medication that an individual can take:
    • Medicines that treat the cause of the disease – antibiotics
    • Medicines which treat the symptoms of the disease – eg. painkillers
  • Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body
  • The use of antibiotics has greatly reduced the deaths from infections in the last century
  • Only certain antibiotics will work on certain diseases, however, so a doctor will prescribe different antibiotics depending on the type of infection (see Culturing Microorganisms)
  • It is important that specific bacteria should be treated by specific antibiotics that are known to work against them
  • Antibiotics work by stopping bacteria cellular processes such as the production of the cell wall – they affect processes usually only in bacteria so are not harmful to animal cells


How antibiotics work, IGCSE & GCSE Biology revision notes

Penicillin was the first antibiotic to be discovered and is widely used, although resistance is a problem

  • Antibiotics will not work against viruses, as viruses reproduce inside cells. It is difficult to develop drugs that kill viruses without also damaging the body’s tissues
  • Painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens (eg. ibuprofen can reduce pain and inflammation)

Antibiotic Resistance

  • The use of antibiotics has increased exponentially since they were first introduced in the 1930s
  • In that time they have saved millions of lives


Antibiotic effect, downloadable IGCSE & GCSE Biology revision notes

The introduction of antibiotics has had one of the largest impacts on global health, shown by this example in the USA

  • However, since their discovery and widespread use, antibiotics have been overused and antibiotic resistance has developed in many different types of bacterial species
    • Bacteria, like all organisms, have random mutations in their DNA
    • One of these mutations may give them resistance to an antibiotic
    • If an organism is infected with bacteria and some of them have resistance, they are likely to survive treatment with antibiotic
    • The population of the resistant bacteria will increase
    • If the resistant strain is causing a serious infection then another antibiotic will be needed
    • A strain of Staphylococcus aureus has developed resistance to a powerful antibiotic methicillin, this is known as MRSA (Methicillin resistant Staphylococcus aureus)
    • MRSA can infect wounds and is difficult to treat without antibiotics

Antibiotic_resistance, IGCSE & GCSE Biology revision notes

Bacteria evolve rapidly as they reproduce quickly and acquire random mutations – some of which confer resistance

Preventing resistant bacteria

  • To reduce the number of bacteria that are becoming resistant to antibiotics:
    • Doctors need to avoid the overuse of antibiotics, prescribing them only when needed – they may test the bacteria first to make sure that they prescribe the correct antibiotic
    • Antibiotics shouldn’t be used in non-serious infections that the immune system will ‘clear up’
    • Antibiotics shouldn’t be used for viral infections
    • Patients need to finish the whole course of antibiotics so that all the bacteria are killed and none are left to mutate to resistant strains
    • Antibiotics use should be reduced in industries such as agriculture – controls are now in place to limit their use in farming

Reducing the spread of resistant strains

  • Good hygiene practices such as handwashing and the use of hand sanitisers have reduced the rates of resistant strains of bacteria, such as MRSA, in hospitals
  • The isolation of infected patients to prevent the spread of resistant strains, in particular in surgical wards where MRSA can infect surgical wounds

Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.

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