BI-1386
Lock-and-key model
Biology · Secondary 4 · Hard · Lock-and-key model
A student adds amylase solution to starch in a test tube and keeps it at 37 °C. Every 2 minutes, she removes a drop and tests it with iodine solution.
At 0 min: blue-black
At 4 min: brown
At 8 min: yellow
Which statement best explains these results using the lock-and-key hypothesis?
At 0 min: blue-black
At 4 min: brown
At 8 min: yellow
Which statement best explains these results using the lock-and-key hypothesis?
- Starch molecules fit into amylase’s active site and are broken down, so less starch remains to react with iodine.
- Amylase changes shape to fit starch, so iodine no longer reacts with starch.
- Iodine blocks the active site of amylase, so starch cannot bind after 4 minutes.
- Starch acts as the enzyme and amylase is the substrate, so iodine colour fades.
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