Immobilised enzymes (BAT)

Question 1

State the two main ways enzyme immobilisation can be achieved.

Answer 1

1) Entrapment- held inside a gel, e.g. silica gel

2) Micro-encapsulation- trapped inside a micro-capsule, e.g. alginate beads

Question 2

What are immobilised enzymes?

Answer 2

Enzymes which are attached to an inert insoluble material over which the substrate passes and the reaction takes place.

Question 3

Give an example of an application of immobilised enzymes.

Answer 3

Biosensors

Question 4

Why are immobilised enzymes important in industrial processes?

Answer 4

• Enzymes are easily recovered for reuse

• Improves enzyme stability in variable/extreme temperatures and pH (compared to free enzymes)

• Enzymes can be easily added or removed, giving greater control over the reaction

Question 5

State the two main inert matrix examples.

Answer 5

1) Sodium alginate beads
2) Cellulose microfibrils

Question 6

Compare the volume to surface area ratio of large beads to smaller beads.

Answer 6

If a given material is used to make large beads, there will be a smaller total surface area, than for smaller beads.

If smaller beads are made, the substrate molecule will have easier access to enzyme molecules, producing a higher rate of reaction.

Question 7

Advantages of immobilising enzymes with a polymer matrix?

Answer 7

• Makes them more stable- it creates a microenvironment allowing reactions to occur at higher temps/more extreme pHs than normal

• Trapping an enzyme molecule prevents the shape change (which denatures AS) so the enzyme can be used in a wide range of physical conditions (compared to if it was free in solution)

Question 8

Why do enzymes immobilised in beads have a lower rate of reaction than those enzymes immobilised on a membrane? (if all other factors are constant)

Answer 8

Some of the active sites are inside the beads, and the substrate takes time to diffuse to them.

Enzymes on a membrane are readily available for binding (-> higher reaction rate)

Question 9

What is a biosensor?

Answer 9

A device that combines a biomolecule, such as an enzyme, with a transducer, to produce an electrical signal which measures the concentration of one type of molecule from a mixture.

Question 10

Describe three advantages of testing blood glucose using a biosensor over the Benedict’s test.

Answer 10

1) Biosensor is specific and will only detect glucose, whereas the Benedict’s test could detect the presence of any reducing sugar.

2) Biosensors can detect far lower concentrations than the Benedict’s test.

3) Result is quantitative, unlike the Benedict’s test which is qualitative (relies on a colour change)