CAIE A Level Biology 9700 · Enzymes
Cellulase is an extracellular enzyme secreted by certain fungi. It catalyses the hydrolysis of cellulose to glucose. Two hypotheses used to describe enzyme action are the lock-and-key hypothesis and the induced-fit hypothesis.
Explain how the lock-and-key hypothesis and the induced-fit hypothesis differ in their description of the formation of the enzyme-substrate complex, and how each hypothesis relates to the lowering of activation energy.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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