Antibiotics, culturing microorganisms and new medicines — Edexcel GCSE Combined Science
How antibiotics treat bacterial but not viral infections, and the stages of discovering, developing and testing new medicines.
Revision notes
2 short notes, in the order of the specification. Each one in short:
Antibiotics are medicines that treat bacterial infections by inhibiting cell processes in the bacterium, without harming the host's own cells. They cannot treat viral diseases such as HIV, colds or flu, because viruses are not cells. Viruses live and reproduce inside host cells, so they do not have the cell processes that antibiotics inhibit.
Developing a new medicine has four stages: discovery, development, preclinical testing and clinical testing. In preclinical testing the medicine is tested on cells, tissues and then live animals to check whether it is toxic and whether it works. In clinical testing it is given first to a few healthy volunteers, then to patients to find the right dose.
Exam questions
2 exam-style questions (4 marks), each with its mark scheme.
Answer the questionsFlashcards
3 cards: flip them, mark what you knew, and practise the rest.
Practise the cardsMind map
The whole of health, disease and the development of medicines on one page, so you can see where this subtopic fits.
Open the mind mapPrint it
Free PDFs to print or save.
Quick check questions
Why can antibiotics not be used to treat viral infections?
Show answer
Antibiotics inhibit cell processes in bacteria; viruses are not cells and reproduce inside host cells.
Triple only: why is an inoculating loop heated in a flame before use?
Show answer
To sterilise it by killing any microorganisms on it.
Triple only: in the core practical, what does a larger clear zone show?
Show answer
The substance is more effective at stopping bacteria growing.
Name the four stages in developing a new medicine in order.
Show answer
Discovery, development, preclinical testing, clinical testing.
Triple only, Higher tier: what is a hybridoma cell?
Show answer
A cell made by fusing an antibody-producing lymphocyte with a tumour cell; it divides and produces antibodies.
Frequently asked questions
Why can't antibiotics kill viruses?
Antibiotics cannot kill viruses because they work by inhibiting cell processes in bacteria, and viruses are not cells. Viruses live and reproduce inside host cells, so they do not have the cell processes that antibiotics target. This is why antibiotics cannot be used to treat viral diseases such as HIV, colds or flu.
What are the stages of developing a new medicine?
New medicines go through four stages: discovery of a chemical that might treat the disease, development to improve it, preclinical testing on cells, tissues and live animals to check toxicity and effectiveness, and clinical testing on people. Clinical testing starts with a few healthy volunteers to check safety, then patients to find the dose.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026