CAIE A Level Biology 9700 · Enzymes
A student measures the Michaelis-Menten constant (Km) of two enzymes, lactase and sucrase, for their respective substrates (lactose and sucrose) under identical conditions. The results are shown in the table below.
| Enzyme | Substrate | Km (mM) |
|---|---|---|
| Lactase | Lactose | 0.2 |
| Sucrase | Sucrose | 2.5 |
Compare the affinity of these two enzymes for their substrates.
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.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
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