A-LevelBiologyEnzymes9700/12 · May/June 2021 · Q121 Mark
The diagram shows sucrose and sucralose. [Figure 12.1] The enzyme sucrase breaks down sucrose but cannot break down sucralose. Four students were asked to suggest why sucrase can break down sucrose but not sucralose. Three of the students gave correct suggestions. Which suggestion cannot be correct?
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
AThe Cl atoms change the shape of the sucralose molecule so it is not the same shape as the active site of sucrase.
BThe Cl atoms of the modified fructose cannot bind to the active site of sucrase.
CThe Cl atoms cannot cause an induced fit, so sucralose does not enter the active site of sucrase.
DThe Cl atoms cause fewer temporary hydrogen bonds between sucralose and the active site of sucrase.
✓ Correct answer
A: The Cl atoms change the shape of the sucralose molecule so it is not the same shape as the active site of sucrase.
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