• Non-protein components
  • Bind temporarily
  • Obtained from diet (iron ions, calcium ions etc)
  • eg, amylase requires Cl⁻ to function


  • An organic (carbon-based) co-factor
  • Bind temporarily
  • Many derived from vitamins
  • Carry chemicals between enzymes

Prosthetic Groups

  • Bind permanently
  • Eg haem in haemoglobin

Activation of Enzymes

  • many enzymes are inactive to begin with
  • need a change in 3D structure to activate
  • Some activated by co-factors, some a change in environment (pH/temperature)