CAIE A Level Biology 9700 · Enzymes
A student investigates the hydrolysis of a disaccharide by the enzyme sucrase. In the absence of sucrase, the reaction requires an activation energy of 128 kJ mol⁻¹. When sucrase is added, the activation energy is reduced to 52 kJ mol⁻¹.
Describe how an enzyme such as sucrase lowers the activation energy of a reaction. In your answer, refer to the active site, the formation of an enzyme-substrate complex, and the lock-and-key and induced-fit models of enzyme action.
6 marks, so the mark scheme is looking for about 6 separate creditworthy points. Making the same point twice in different words earns it once.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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