CAIE A Level Biology 9700 · Enzymes
In a metabolic pathway, an enzyme catalyses the conversion of substrate to product. The activation energy for the uncatalysed reaction is 120 kJ mol, but in the presence of the enzyme it is reduced to 45 kJ mol. Describe how the enzyme achieves this reduction in activation energy. Include in your answer the roles of the active site and the formation of the enzyme-substrate complex, and refer to the lock-and-key and induced-fit hypotheses.
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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