Scheme of Work Cambridge International as & a level

Extension activity: Learners carry out research into non-hydrolytic enzymes. Some synthesise macromolecules, some transfer a chemical group, and some rearrange atoms in a molecule. Encourage learners to draw sketches of how this happens.

3.1.3 Investigate the progress of enzyme-catalysed reactions by measuring rates of formation of products using catalase and rates of disappearance of substrate using amylase. 3.1.4 Outline the use of a colorimeter for measuring the progress of enzyme-catalysed reactions that involve colour changes.

Learners suggest how enzyme activity can be measured. Discuss with learners what features the substrate and product must show for this to be possible. For example, the substrate or product must be detectable, either due to a colour change, a change in pH, and so on. Host practical activities for learners to investigate enzyme-catalysed reactions. These may include: Following the course of an enzyme-catalysed reaction using amylase. Learners plot a graph of the concentration of starch (x-axis) against absorbance (y-axis) to measure the reduction in the intensity of the blue-black colour. Learners measure the rate of reaction by measuring the rate of formation of a product, using catalase (from celery) and the breakdown of hydrogen peroxide. Using other means to track the progress of an enzyme-catalysed reaction. Another example is at: www.saps.org.uk/secondary/teaching-resources/293-student-sheet-24-microscale-investigations-with-catalase Further information related to these practical activities are at: www.nuffieldfoundation.org/practical-biology/factors-affecting-enzyme-activity Prepare three or four past paper questions, ideally of a multiple-choice or short-answer nature, which learners complete and pass to you as they leave the room. This ‘exit card’ technique can provide an opportunity for formative assessment to inform you whether you need to reinforce the content in the next lesson. (F)

3.2 Factors that affect enzyme action