Temperature & enzyme activity (Edexcel Int. A-level Biology)

This lesson explains the effects of temperature on the rate of enzyme activity and describes how to calculate the temperature coefficient. The PowerPoint and the accompanying resources have been designed to cover point 5.21 of the Edexcel International A-level Biology specification and this lesson has been specifically planned to tie in with a lesson in topic 2 where the roles and mechanism of action of enzymes were introduced.

The lesson begins by challenging the students to recognise optimum as a key term from its 6 synonyms that are shown on the board. Time is taken to ensure that the students understand that the optimum temperature is the temperature at which the most enzyme-product complexes are produced per second and therefore the temperature at which the rate of an enzyme-controlled reaction works at its maximum. The optimum temperatures of DNA polymerase in humans and in a thermophilic bacteria and RUBISCO in a tomato plant are used to demonstrate how different enzymes have different optimum temperatures and the roles of the latter two in the PCR and photosynthesis are briefly described to prepare students for these lessons in modules 6 and 5.

Moving forwards, the next part of the lesson focuses on enzyme activity at temperatures below the optimum and at temperatures above the optimum. Students will understand that increasing the temperature increases the kinetic energy of the enzyme and substrate molecules, and this increases the likelihood of successful collisions and the production of enzyme-substrate and enzyme-product complexes. When considering the effect of increasing the temperature above the optimum, continual references are made to the previous lesson and the control of the shape of the active site by the tertiary structure. Students will be able to describe how the hydrogen and ionic bonds in the tertiary structure are broken by the vibrations associated with higher temperatures and are challenged to complete the graph to show how the rate of reaction decreases to 0 when the enzyme has denatured.

The final part of the lesson introduces the Q10 temperature coefficient and students are challenged to apply this formula to calculate the value for a chemical reaction and a metabolic reaction to determine that enzyme-catalysed reactions have higher rates of reaction