Biology / Science GCSE: Investigate the effect of pH on enzyme activity

This video demonstrates the GCSE Biology and Combined Science required practical to investigate the effect of pH on enzyme activity included in AQA, Edexcel and OCR specifications.

This video investigates the effect of pH on the enzyme amylase, with which students should be familiar having studied it linked with digestion.

This investigation requires high levels of organisation and working to specific, short intervals of time and can be challenging for students to manipulate. This video slows the process down, exploring each step.

Teacher Notes

The practical supports Development of Apparatus & Techniques Biology 1, 2 and 5 (DfE GCSE subject content guidance, Appendix 4).

This video could be used after students have attempted the investigation to support understanding of the steps involved and the purpose of each step. As the investigation is quite fast paced, these messages can easily be missed during the process.

It is likely that students will be following a prescribed method for this investigation and therefore, exploring the method step-by-step after completing the investigation can help to ensure understanding.

The video can also be used to reinforce the impact of different variables in the investigation: dependent, independent and control variables.

Finally, the video can be used to explore ways to improve the accuracy of the investigation.

Points for discussion:
This practical is challenging for students to manage and good organisation is key.

Students are working to time and sampling frequently which reduces the opportunity to process the purpose of each step.

Students often find justification of method steps difficult, even when they can recall a practical method.

This video works through the practical method, exploring the purpose of each step and the apparatus used.

The video also identifies the different variables that can affect the investigation: dependent, independent and control. This is something that students often struggle to identify at GCSE.

The video also focuses on specific improvements which can be made to improve the outcome of the investigation, again something students find challenging.

Suggested activities:
Students could be asked to suggest further improvements to this practical, for example to investigate at different pH values.

They could also be asked to design a follow-on investigation, for example to investigate the effect of changing temperature on the rate of enzyme reaction.

For each alternative, students should be encouraged to identify the different types of variable, to justify their apparatus choice and explain the purpose of each step of the method.

Showing students investigations or data linked to using different enzymes and/or a different independent variable could support them in answering questions that may be set in unfamiliar contexts.

Curriculum Notes

Suitable for teaching Biology and Combined Science at Key Stage 4 and GCSE in England, Wales and Northern Ireland, and at National 4 and 5 in Scotland.

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