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GCSE Biology · key term
The temporary combination formed when a substrate is bound to an enzyme's active site.
Used by AQA, Edexcel and OCR
Specification 4.2.2.1 · Paper 1
A temporary association formed when a substrate is bound to an enzyme’s active site.
Revise: The Mechanism and Factors of Enzyme ActionA correctly shaped substrate binds to the active site, forming a temporary enzyme–substrate complex.
Specification 1.7, 1.9 · Paper 1, Paper 2
Revise: Mechanism of Enzyme ActionThis temporary combination is an enzyme–substrate complex.
Specification B1.2g · Paper 1 (Foundation), Paper 3 (Higher)
Revise: Enzyme Mechanism and MetabolismWhen a suitable substrate collides with the active site, it can bind there temporarily. This produces an enzyme–substrate complex.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
Revise: EnzymesWhen substrate particles move and collide with an enzyme, a correctly shaped substrate can bind inside the active site. This forms a temporary enzyme–substrate complex. The enzyme catalyses the conversion of substrate into product while the substrate is held at the active site.
When explaining specificity, link the enzyme’s active-site shape to the complementary shape of its substrate, then state that an enzyme–substrate complex forms.
For high temperature or extreme pH, explain the whole chain: bonds are disrupted, the enzyme’s shape changes, the active site is no longer complementary, fewer enzyme–substrate complexes form, and the rate decreases.
For a mechanism question, give the sequence: substrate binds, enzyme–substrate complex forms, reaction occurs, products leave and the enzyme can be reused.
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