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Combined Science
Key terms
Lock and key hypothesis

GCSE Combined Science · key term

Lock and key hypothesis

Definition

A simplified model of enzyme action in which a substrate fits an enzyme’s active site like a key fits a lock.

Used by OCR

How each exam board covers it

OCR GCSE Combined Science A · J250

Specification B1.2d · Biology Paper 1

The lock and key hypothesis is a simplified model of this process. The enzyme is like a lock, and its substrate is like the key that fits. A differently shaped substrate cannot fit the active site, so that enzyme cannot catalyse its reaction.
Revise: Mechanism of Enzyme Action

OCR Combined Science A past papers

Related key terms

Active site
Denaturation
Enzyme
Enzyme specificity
Enzyme–substrate complex

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Lock and key hypothesis — OCR GCSE Combined Science A Definition