Enzyme Activity: Immobilised v Free (Cambridge (CIE) AS Biology): Revision Note

Exam code: 9700

Cara Head

Written by: Cara Head

Reviewed by: Alistair Marjot

Updated on

Enzyme activity: immobilised v free

  • Enzymes can be added to solutions and are thereby considered ‘free’ or they can be immobilised

    • Investigations with free enzymes are carried out with an enzyme added to a solution

    • Depending on the needs of an investigation, substrate can be added directly to the solution or the enzyme solution can be added in a more controlled way to a substrate

  • 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

    • Lactose is a disaccharide that is broken down into glucose and galactose

    • 5-10% of the UK population are lactose intolerant

Diagram of milk being poured through alginate beads with lactase, breaking lactose into glucose and galactose, producing lactose-free milk.
Using immobilised enzyme to modify milk
  • Using the enzyme 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

Diagram of lactase enzyme breaking down lactose disaccharide into glucose and galactose monosaccharides, showing substrate and product labels.
Lactose is a disaccharide that is broken down by lactase into the monosaccharides glucose and galactose

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Cara Head

Author: Cara Head

Expertise: Biology & Psychology Content Creator

Cara graduated from the University of Exeter in 2005 with a degree in Biological Sciences. She has fifteen years of experience teaching the Sciences at KS3 to KS5, and Psychology at A-Level. Cara has taught in a range of secondary schools across the South West of England before joining the team at SME. Cara is passionate about Biology and creating resources that bring the subject alive and deepen students' understanding

Alistair Marjot

Reviewer: Alistair Marjot

Expertise: Environmental Systems and Societies & Biology Content Creator

Alistair graduated from Oxford University 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 & Societies. Alistair has continued to pursue his interests in ecology and environmental science, recently gaining an MSc in Wildlife Biology & Conservation with Edinburgh Napier University.