Scheme of Work Cambridge International as & a level

KC2 KC6

3.2.1 Investigate and explain the effects of the following factors on the rate of enzyme-catalysed reactions: temperature pH (using buffer solutions) enzyme concentration substrate concentration inhibitor concentration.

Resource Plus Carry out the Investigating the effect of temperature on an enzyme-catalysed reaction experiment referring to the Teaching Pack for lesson plans and resources. Proteases such as trypsin catalyse the hydrolysis of the protein casein, which gives milk its white colour. Learners investigate the rate of decolourisation of milk due to the hydrolysis of casein, providing a way to investigate how a change in temperature affects the rate of the reaction. Learners plan a laboratory method, analyse the difference between quantitative and qualitative data, and interpret measurements of reaction rate. Practical tasks that address the syllabus outcomes include the following: Investigating the effect of temperature on the activity of trypsin in a reaction that catalyses the breakdown of opaque casein into a translucent solution. Analysing the effect of substrate (hydrogen peroxide) concentration on the activity of catalase. Investigating the effect of enzyme concentration on the activity of rennin. Investigating the effect of pH on the activity of amylase by recording the disappearance of a substrate by testing for starch with iodine solution on a spotting tile. Further information related to these practical activities is at: www.nuffieldfoundation.org/practical-biology/factors-affecting-enzyme-activity This series of practical activities provides a large number of opportunities to help learners understand what is meant by the independent variable, dependent variable, and standardised variables in an investigation. Help learners appreciate this by ‘standardising’ statements in writing frames, such as ‘an investigation into the effect of X and Y, while keeping A, B and C the same.’ A significant number of key terms are introduced in this topic. To help familiarise learners with them, learners work in pairs to describe key words/terms to each other, but without using other (listed) key words. For example, challenge learners to describe the effect of high temperatures on human enzyme activity without using the three key terms: denature, bonds, and active site. (F)