AQA AS 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.

Author: Amelia

While studying Biochemistry at Oxford University, Amelia started her own tutoring service, helping to connect Science tutors with students in her local area. Amelia has experience teaching the sciences and Maths at all levels to UK and international students and, as well as being our Biology Lead, designs revision resources for Chemistry.
Close

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top