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Factors that affect the rate of reactionEnzymes [GCSE Chemistry only]

Chemical reaction rates increase or decrease according to factors including temperature, pressure and light. A catalyst changes the rate of reaction but is unchanged at the end of the reaction.

Part of Chemistry (Single Science)Rate of chemical change

Enzymes [GCSE Chemistry only]

Enzymes are biological catalysts and are produced by living organisms to speed up the reactions they need in order to survive.

Without the use of catalysts, these biochemical processes (such as and ) would happen too slowly and the organism would not survive.

Different enzymes require different conditions to work at their highest activity (known as the optimal conditions), but most require a temperature close to 37掳C (human body temperature). If temperatures exceed the optimal temperature, the enzyme can become denatured and stop working properly.

Graph of rate against temperature (掳C) for enzymes.

Enzymes are often more effective than any non-biological alternatives, and so they are used commercially to speed up a number of different reactions. This includes uses in:

  • washing powder
  • brewing (using yeast to ferment sugar into ethanol)
  • making cheese

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