CIE A Level Biology (9700) 2019-2021

Revision Notes

3.2.8 Enzyme Activity: Immobilised v Free

Enzyme Activity: Immobilised v Free

  • Enzymes can be added to solutions and are thereby considered ‘free’ or they can be immobilised
  • Immobilised enzymes are enzymes that have been bound to an inert, stationary and insoluble material such as alginate
  • The substrate is then passed over the immobilised enzyme and the product is collected
  • Advantages to this method:
    • There is no enzyme in the product (the product is uncontaminated) and therefore there is no need to further process or filter the end product
    • The immobilised enzyme can be reused multiple times which is both efficient and cost-effective (enzymes are expensive)
    • Immobilised enzymes have a greater tolerance of temperature and pH changes (immobilisation often makes enzymes more stable)
  • A practical application of immobilised enzymes used in the food industry is in the production of lactose-free milk:
    • Milk is a valuable source of nutrients containing protein, fat and the carbohydrate Lactose
    • 5-10% of the UK population are lactose intolerant
    • Lactose is a disaccharide that is broken down into glucose and galactose

Immobilised enzymes - lactase, downloadable AS & A Level Biology revision notes

Using immobilised enzyme to modify milk

  • Using lactase as shown above is an efficient way to remove lactose from milk and to provide lactose intolerant individuals with a way of consuming milk without suffering intolerance symptoms:
    • The enzyme lactase can be immobilised using alginate beads
    • Milk is run through the column of lactase-containing beads
    • The lactase hydrolyses the lactose in the milk to glucose and galactose
    • This ensures the milk is lactose-free
    • It can also then be used to make other lactose-free dairy products

Hydrolysis of lactose, downloadable AS & A Level Biology revision notes

Lactose is a disaccharide that is broken down by lactase into the monosaccharides glucose and galactose


Alistair graduated from Oxford University in 2014 with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems and Societies.

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