AQA A Level Biology

Revision Notes

1.4.1 Many Proteins are Enzymes

Enzymes as Proteins

  • Enzymes are biological catalysts
    • ‘Biological’ because they function in living systems
    • ‘Catalysts’ because they speed up the rate of chemical reactions without being used up or changed
  • Enzymes are also globular proteins
  • Critical to the enzyme’s function is the active site where the substrate binds
  • Metabolic pathways are controlled by enzymes in a biochemical cascade of reactions
    • Virtually every metabolic reaction within living organisms is catalysed by an enzyme – enzymes are therefore essential for life to exist
  • Enzymes can be intracellular or extracellular referring to whether they are active inside or outside the cell respectively
  • Intracellular enzymes are produced and function inside the cell
  • Extracellular enzymes are secreted by cells and catalyse reactions outside cells (eg. digestive enzymes in the gut)

Enzymes Table

Enzymes table, downloadable AS & A Level Biology revision notes

Exam Tip

Don’t forget that enzymes are proteins and so anything that could denature a protein, rendering it non-operational (extremes of heat, temperature, pH etc.) would also denature an enzyme.

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