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GCSE Biology · key term
The point at which the chosen measurable change shows that a reaction has finished or reached a specified stage.
Used by Edexcel and OCR
Specification 1.11 · Paper 1, Paper 2
Revise: Rate CalculationsSome enzyme investigations record only the time needed to reach a fixed end point. For example, a starch-and-amylase mixture can be sampled into iodine until the iodine remains orange, indicating that starch is no longer detected. If each trial begins with the same amount of substrate and uses the same end point, each trial represents the same overall change.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
The point at which an investigation's chosen test shows that a reaction has reached a specified stage.
Revise: TechniquesRecord when a sample no longer turns the iodine blue-black. That is the chosen end point: starch is no longer detected by this test.
If every trial uses the same end point, calculate relative rate using . Do not report the time itself as the rate.
For the iodine test, the end point is when a fresh sample no longer turns the iodine blue-black.
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