- These are enzymes that are fixed, bound or trapped in an inert matrix e.g alginate beadss.
- They can be packed into glass columns
- Substrate can be added to the top of the column and reacts with the enzyme as it slowly flows down.
- Once set up the column can be used again and again
- As the enzyme is fixed it doesn't mix up with the products therefore cheaper to seperate
- Immobilising enzymes creates micro environments allowing reactions to occur at higher temperatures than normal.
- Enzymes can tolerate wider range of conditions
- Enzymes are easily recovered, reducing overall cost
- Several enzymes with different optimal conditions can be used
- Enzymes can easily be added or removed giving greater control of the reaction
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- Biosensors work on principle that enzymes are specific and are able to select one type of molecule from a mixture.
- Can be used in the accurate detection of minute traces.
- Detection of blood sugar in diabetics
- The electrode probe has specific immobilised enzyme in a membrane and is placed in the blood sample.
- If glucose is present, it diffuse through the membrane and forms enzyme-substrate complex.
- This produces a small electric current which is picked up by the elecctrode which is read by the meter.
- Normal blood glucose levels are 3.89-5.83 mmol dm-3
Steps of using a biosensor:
- Blood contains a mixture of different molecules
- Enzyme electrode is placed in a blood sample
- Glucose diffuse through membrane enzyme layer
- Oxygen is taken up
- Rate of oxygen uptake is proportional to glucose concentration
- Digital shows accurate concentration of glucose.
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