# A student reads about the development of penicillin. Alexander Fleming noticed in 1928 that a mould called Penicillium was killing bacteria growing on a Petri dish. Decades later, penicillin became one of the most widely used medicines in the world. Explain why penicillin can be described as a naturally occurring substance and outline the key stages that would have been needed before penicillin could be approved for use as a medicine.

> OCR A-Level Chemistry B: Salters (H433) — WM What's in a medicine? · Explain · 5 marks

> Alexander Fleming discovered in 1928 that the mould Penicillium produced a substance that killed bacteria. This substance was eventually developed into the antibiotic medicine penicillin, which is used to treat bacterial infections.

## Mark scheme (5 marks)

1. Penicillin is naturally occurring because it is extracted/produced from a living organism (the mould Penicillium / a fungus)
2. The active ingredient/substance would need to be extracted and purified from the mould
3. The medicine must be tested to check it is safe (does not harm the patient / no harmful side effects)
4. The medicine must be tested to show it is effective / that it works against bacterial infections
5. Clinical trials must be carried out (tested on humans) before the medicine can be approved/sold

## Key terms

- [naturally occurring](https://www.gradenine.co.uk/glossary/naturally-occurring)

## Related

- [Revision notes for OCR A-Level Chemistry B: Salters (H433)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-reads-about-the-development-5242c676) · Published by Druglandscape Ltd.