# A student wants to use an autoclave before culturing bacteria on agar plates in a school laboratory. Explain why an autoclave is used as part of aseptic techniques, and describe what would happen to results if the agar plates and equipment were not sterilised before use.

> Pearson Edexcel A-Level Biology A (9BI0) — 5.1 Microbial growth and culture · Explain · 5 marks

> A student is preparing to culture a known, safe strain of bacteria. They have access to an autoclave, agar plates, inoculating loops and a growth medium containing carbohydrates, proteins, vitamins and minerals.

## Mark scheme (5 marks)

1. An autoclave sterilises equipment / agar plates by exposing them to high temperatures (and pressure)
2. This kills any microorganisms / pathogens already present on the equipment or agar plates before culturing begins
3. If equipment / agar plates are not sterilised, contaminating microorganisms from the environment would grow on the agar plates
4. This contamination would make it impossible to identify which colonies belong to the intended bacterial strain / results would be unreliable
5. Unsterilised equipment could also introduce pathogens, creating a health risk to the student

## Key terms

- [autoclave](https://www.gradenine.co.uk/glossary/autoclave)
- [aseptic techniques](https://www.gradenine.co.uk/glossary/aseptic-techniques)
- [agar plate](https://www.gradenine.co.uk/glossary/agar-plate)
- [sterilise](https://www.gradenine.co.uk/glossary/sterilise)

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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-wants-to-use-an-12dd49a5) · Published by Druglandscape Ltd.