Biology BY1-biosensors

- Immobilised enzymes are enzyme molecules that are trapped on an inert matrix such as alginate beads

-they are used in medicine and industry (e.g biosensors or to make lactose-free milk)

-Enzymes are found in the outside of the matrix so that they can react with the substrate

-the beads are usually packed into glass columns.The substrate slowly flows down the column and enzyme-substrate complexes are formed. 

-no purification is needed because the enzyme is fixed so it doesnt get mixed with the product

-the reaction is easy to control because the amount of substrate can be controlled very easily

-enzymes are able to withstand higher temperatures and ph's and different enzymes can be used at the same time

-it's a lot cheaper

-the enzymes can be reused easily

- it's the association of an enzyme with a transducer which produces an electrical signal in response to substrate trasformation

-biosensors work on the principal that enzymes are specific and only work with one type of molecule, so they can detect a specific molecule even in low amounts of substrate.

- biosensors are used to detect levels of glucose in blood

As urea molecules penetrate through the membrane, they bind to the active sites of urase enzymes. The enzyme catalyses the reaction and ammonium ion are produced. The higher the concentration of urea molecules, the greater the number of ammonium ions prouced.The ammonium ions will produce a small current which can be detected by the transducer and a digital reading will be displayed.

Molecules of other solutes which may be present will not affect the reuslt because the partially-permiable membrane will only allow the urea molecules to diffuse through the membrane and so it prevents the passage of other molecules.

The temperature of the biosensor should be kept constant because higher temperature will increase the rate of reaction as molecules will have mole kinetic energy and therefore will collide more frequently. Similarly,the temperature will affect the rate of diffusion