15.2) Medicinal drugs

15.2) Medicinal drugs



Antibiotics attack bacteria in a variety of ways

  • Disrupt the production of the cell wall and so prevent the bacteria from reproducing, or even cause them to burst open.
  • Interfere with protein synthesis and thus arrest bacterial growth.


Animal cells do not have cell walls, and the cell structures involved in protein production are different. Consequently, antibiotics do no damage human cells although they may produce some side effects such as allergic reactions.


Development of resistant bacteria:

  • If a course of antibiotics is not completed, some of the bacteria it is being used to destroy will not be killed, but will have been exposed to the drug..
  • Some of the survivors may be drug-resistant mutants. When they reproduce, all their offspring will have the drug resistance, so the antibiotic will become less effective.
  • MRSA (methicillin-resistant Staphylococcus aureus). A type of bacteria that has developed resistance to a number of widely used antibiotics.
  • Development of this can be minimised by using antibiotics only when essential and ensuring treatment is completed.


Antibiotics and viral diseases:

  • Antibiotics are not effective against viral diseases.
  • This is because antibiotics work by disrupting structures in bacteria such as cell walls and membranes, or processes associated with protein synthesis and replication of DNA.
  • Viruses have totally different characteristics to bacteria, so antibiotics do not affect them.