This lesson describes the structure of enzymes and explains how their specificity enables them to act as catalysts intracellularly and extracellularly. The engaging PowerPoint and accompanying resources have been designed to cover points 1.5 (i), (ii), (iii) & (vii) of the Edexcel A-level Biology B specification and describes Fischer’s lock and key hypothesis and Koshland’s induced-fit model to deepen student understanding of the mechanism of enzyme action
The lesson has been specifically planned to tie in with topic 1.3 where protein structure and globular proteins were covered. This prior knowledge is tested through a series of exam-style questions along with current understanding and mark schemes are included in the PowerPoint so that students can assess their answers.
Students will learn that enzymes are large globular proteins which contain an active site that consists of a small number of amino acids. Emil Fischer’s lock and key hypothesis is introduced to enable students to recognise that their specificity is the result of an active site that is complementary in shape to a single type of substrate. Time is taken to discuss key details such as the control of the shape of the active site by the tertiary structure of the protein. The induced-fit model is described so students can understand how the enzyme-susbtrate complex is stabilised and then students are challenged to order the sequence of events in an enzyme-controlled reaction.
The lesson finishes with a focus on ATP synthase, DNA helicase and DNA polymerase and students are challenged on their recall of DNA replication with an exam question before they are challenged on their knowledge of carbohydrates, lipids and proteins from topics 1.1 - 1.3 as they have to recognise some extracellular digestive enzymes from descriptions of their substrates.
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