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Combined Science
Key terms
Enzyme

GCSE Combined Science · key term

Enzyme

Definition

A protein that acts as a biological catalyst, speeding up a chemical reaction without being used up.

Used by AQA and Edexcel

How each exam board covers it

AQA GCSE Combined Science Trilogy · 8464

Specification 4.2.2.1, 4.4.2.3, 5.6.1.4 · Paper 1, Paper 2, Paper 4

Digestion, photosynthesis and respiration all involve reactions catalysed by enzymes.
Revise: Enzyme action and investigating pH
A biological catalyst that speeds up a chemical reaction without being used up.
Revise: Metabolism
Revise: Principles of Homeostasis

1 more note

A biological catalyst that speeds up reactions in living systems without being used up overall.
Revise: Chemical Catalysts

AQA Combined Science Trilogy past papers

Edexcel GCSE Combined Science · 1SC0

Specification Rates of reaction · Paper 1, Paper 2, Paper 3, Paper 4

A biological catalyst, usually a protein, that speeds up a chemical reaction without being used up.
Enzymes are biological catalysts. They speed up reactions without being used up, so the same enzyme can catalyse a reaction repeatedly.
Revise: Enzymes
A biological catalyst produced by a living organism.
Revise: Rates of reaction

Edexcel Combined Science past papers

Exam tips

1
Explain specificity using the complementary shapes of the substrate and active site, not simply by saying that an enzyme is specific.
2
At high temperatures, enzymes are denatured, not killed. Enzymes are molecules, not living organisms.
3
Do not say that enzymes are ‘killed’ by high temperatures: they can become denatured.

Related key terms

Catalyst
Activation energy
Active site
Amylase
Buffer solution
Denaturation
Enzyme–substrate complex
Metabolism
Rate of reaction
Substrate

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